

.^ .i.» ami iiKiUU ^ 



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1 



JC 



LECTURES 



ON THE 



APPLICATIONS OF CHEMISTRY AND GEOLOGY 



TO 



AGRICULTURE. 



"The profit of tlie earth is for aU; the king himself is served by the field."— 2?cdc». v. 9. 



^ov-- -^,> 



BY JAS. F.W.JOHNSTON, M.A.. F,R.SS.L.&E. 

FELLOW OP THE GEOLOGICAL AND CHEMICAL SOCIETIES, 

Honorary Member of the Royal Agricultural Society, Foreign Member of the Royal 

Swedish Academy of Agriculture, &c. &c. ; Chemist to the Agricultural 

Chemistry Association of Scotland, and Reader in Chemistry 

and Mineralogy in the University of Durham. 



WITH AN APPENDIX, 

CONTAINING SUGGESTIONS FOR EXPERIMENTS IN PRACTICAL AGRICULTURR. 



NEW YORK: 
PUBLISHED BY WILEY & PUTNAM, 

161 BROADWAY. 



1844. 



65^ 






14^*- 



By Transfer from 
U.S. Naval Academy 
Aug. 26 1932 









VENERABLE CHARLES THORP, D.D., F.R.S., &c., dec, 

ARCHDEACON OF DURHAM, AND WARDEN OP THE UNIVERSITY OF DURHAM. 

My dear Sir, — * ' ' 

I cannot more appropriately dedicate the following Lectures than to the head 
of the University with which I am officially connected, and within the walls 
of which the earlier Lectures were first delivered. 

In publishing this Volume I am only endeavouring to follow out the enlight- 
ened intentions of yourself and the other Founders of the University of Dur- 
ham, who have contributed so largely of their fortune and their influence for 
the promotion and diffusion of sound and useful learning. That you have so 
long and so successfully laboured to carry these intentions into effect, is ano- 
ther reason why I desire to dedicate my work especially to you. 

I need scarcely add how much pleasure it affords me to embrace this public 
opportunity of testifying my own personal regard and esteem. 
Believe me, my dear Sir, 

^ ^ With much respect, 

' Your obedient humble servant, 

JAMES F. W. JOHNSTON. 
Durham, lat June, 1844. 



I 



PREFACE. 



The First Part of the following Lectures was addressed 
to a Society* of practical agriculturists, most of whom pos- 
sessed no knowledge whatever of scientific Chemistry or Ge- 
ology. They commence, therefore, with the discussion of 
those elementary principles which are necessary to a proper 
understanding of each branch of the subject. Every thing 
in such Lectures, which is not — or may not be — easily un- 
derstood by those to whom they are addressed, is worse than 
useless. It has been my wish, therefore, to employ no scien- 
tific terms, and to refer to no philosophical principles, which 
I have not previously explained. 

To many who may take up the latter portions of the work, 
some points may appear obscure or difficult to be fully un- 
derstood ; such persons will, I hope, do me the justice to be- 
gin at the beginning, and to blame the Author only when that 
which is necessary to the understanding of the later is not 
to be found in the earlier Lectures. 

For the sake of clearness, I have, in the following pages, 
divided the subject into four Parts — the study of each pre- 
ceding Part preparing the way for a complete understanding 
of those which follow. Thus, Part I. is devoted to the or- 
ganic elements and parts of plants, the nature and sources 
of these elements, and to an explanation of the mode in which 
they become converted into the substance of plants ; — Part 
II., to the ijiorganic elements of plants, comprehending the 
study of the soils from which these elements are derived, and 

* The Durham County Agricultural Society, and the Members of the Dur- 
ham Farmers' Club. 



VI tREPACE. 

the general relations of geology to agriculture ; — Part III., to 
the various methods, mechanical and chemical, by which 
the soil may be improved, and especially to the nature of 
Quanures^ by which soils are made more productive, and the 
amount of vegetable produce increased; — and Part IV., to 
the results of vegetation^ to the kind and value of the food 
produced under different circumstances, and its relation to 
the growth and feeding of cattle, and to the amount and 
quality of dairy produce. 

By this method I have endeavoured to ascend from the 
easy to the apparently diiRcult ; and I trust that the willing 
and attentive reader will find no difficulty in keeping by my 
side during the entire ascent. 

The Author has much pleasure in now presenting these 
Lectures to the public in a complete form. He has only to 
express a hope that the delay which has occurred in the pub- 
lication of the latter part of the work has enabled him to ren- 
der it more useful, and therefore more worthy of the public 
approbation. 

Durham^ Jmie^ 1844. 



Note. — The rapid sale of a large impression having rendered a second 
edition of the first and second Parts necessary before the entire comple- 
tion of the work, such alterations, corrections, and additions only have 
been made as could be introduced without altering the original paging of 
the work. Several oversights, however, have been corrected, and some 
omissions supplied, which presented tliemselves in the earlier edition. 



LECTURES 



ON THE 



APPLICATIONS OF CHEMISTRY AND GEOLOGY 



TO 



AGRICULTURE. 

mvt K. 

ON THE ORGANIC ELEMENTS OF PLANTS, 



CONTENTS. 



TA.B.T Z. 

ON THE ORGANIC CONSTITUENTS OF PLANTS. 



LECTURE I. 

IMPORTANCE OF AGRICULTURE, 

Introduction P-H I Hydrogen, its properties and relations to 

Different kinds and states of matter .21 | vegetable life p. 25 

Carbon, its properties and relations to ve- i Nitrogen, its properties and relations to 

getable life 23 [ vegetable life 26 

Oxygen, its properties and relations to ve- Rewards of study .....27 

getable life 24 | 

LECTURE IL 



CHARACTERISTIC 

Characteristic properties of organic sub- 
stances 28 

Relative proportions of organic elements.. 29 
Of the form or state of combination in 
vfhich the organic elements enter into 
and minister to the growth of plants 31 



PROPERTIES OF ORGANIC SUBSTANCES. 

On the constitution of the atmosphere 31 

The natui'e and laws of chemical combi- 
nation 32 

Of water, and its relations to vegetable life. .36 
Of the cold produced by the evaporation 
of water, and its influence on vegetation. .43 



LECTURE in. 

CARBONIC AND OXALIC ACIDS, THEIR PROPERTIES AND RELATIONS 
Carbonic acid, its properties and relations 



to vegetable life 45 

Oxalic acid, its properties and relations to 

vegetable hfe 47 

Carbonic oxide, its constitution and pro- 
perties ^S 



Light carburetted hydrogen, the gas of 
marshes and of coalmines 49 

Ammonia, its properties and relations to 
vegetable life 50 

Nitric acid, its constitution and properties . .56 

Questions to be considered 57 



LECTURE IV. 



SOURCE OF THE ORGANIC ELEMENTS OF PLANTS, 

Form in which the nitrogen enters into 

the circulation of plants 68 

Absorption of ammonia by plants 70 

Absorption of nitric acid by plants 72 

Conclusions 74 



Source of the carbon of plants 58 

Form in which carbon enters into the cir- 
culation of plants 63 

Source of the hydrogen of plants 64 

Source of the oxygen of plants 66 

Source of the nitrogen of plants ib. 



LECTURE V. 

HOW DOES THE FOOD ENTER INTO THE CIRCULATION OF PLANTS'? 
General structure of plants, and of their 



several parts 75 

The functions of the root 76 

The course of the sap 85 

Functions of the stem.. 88 



Functions of the leaves 89 

Functions of the bark 96 

Circumstances by which the functions of 

the various parts of plants are modified . . 97 
Effects of marling 101 



iv 



CONTENTS OF PART 1. 



LECTURE VI. 

SUBSTANCES OP 'WHICH PLANTS CHIEFLY CONSIST. 



Woody fibre or lignin— its constitution 

and properties p. 103 

Starch — its constitution and properties. . . .106 

Gum — its constitution and properties 108 

Of Sugar— its varieties and chemical con- 
stitution 109 

Mutual relations of woody filjre, starch, 

gum, and sugar Ill 

Mutual transformations of woody fibre, 
, starch, gum, and sugar 112 



Of the fermentation of starch and sugar, 
and of the relative circumstances under 
which cane and grape sugars generally 
occur in nature p. 115 

Of substances which contain nitrogen.— 
Gluten, vegetable albumen, and diastase.116 

Vegetable Acids. — Acetic acid, oxalic acid, 
tartaric acid, citric acid, malic acid 121 

General observations on the substances 
of which plants chiefly consist 126 



LECTURE VIL 

CHEMICAL CHANGES BY WHICH THE SUBSTANCES OF WHICH PLANTS CHIEFLY 
CONSIST ARE FORMED FROM THOSE ON WHICH THEY LIVE. 



Chemical changes which take place du- 
ring germination, and during the devel- 
opement of tlie first leaves and roots.... 130 

Of the chemical changes from the for- 
mation of the true leaf to the expansion 
of the flower 134 

On the production of oxalic acid in the 
leaves and stems of plants 137 



Of the chemical changes between the 
opening of the flower and the ripening 
of the fruit or seed 130, 

Of the chemical changes which take place j 
after the ripening of the fruit and seed..l43-i 

Of the rapidity with which these changes 
take place, and the circumstances by 
which they are promoted 'it. 



LECTURE VIII. 

HOW THE SUPPLY OF FOOD FOR PLANTS IS KEPT UP IN THE GENERAL 
VEGETATION OF THE GLOBE. 



Of the proportion of their carbon which 

flants derive from the atmosphere 145 
the relation which the quantity of car- 
bon extracted by plants from the air, 
bears to the whole quantity contained 

in the atmosphere 147 

How the supply of carbonic acid in the 

atmosphere is renewed and regulated.. 148 
General conclusions in relation thereto. . .155 



Of the supply of ammonia to plants 156 

Of the supply of nitric acid to plants 159 

Theory of the action of nitric acid and 

ammonia .163 

Comparative influence of nitric acid and 

of ammonia in difiFerent climates 166 

Stimulating influence of these compounds, i). 
Concluding observations regarding the 

organic constituents of plants 168 



LECTURE I. 

Importance of Agriculture— Relation of the growth of food to the population of Great Britain — 
Recent progress and prospects of English Agriculture — Application of Chemical and Geo- 
logical Science to the art of culture — to the improvementof soils— the rotation of crops — 
the application of manures, &c.— Outline of the Course of Lectures — Number and nature 
of the elementary bodies — The organic elements Carbon, Hydrogen, Oxygen, and Nilro 
gen, their properties and their relations to vegetable life. 

Were I about to address you in a single or detached Lecture only, I 
should think it my duty to select some one branch of the art of culture 
for special illustration, and without much introductory matter to pro- 
ceed at once to the exposition of the principle or principles on which it 
depended. As the present, however, is only the first of a Series of Lec- 
tures I hope to have the honor of delivering to you, I may be permitted 
to introduce my subject with a few prefatory remarks, which will here 
find their appropriate place. 

In regard to the importance of Agriculture it may appear superfluous 
in me to address you. That art on which a thousand millions of men 
are dependent for their very sustenance — in the prosecution of which 
nine-tenths of the fixed capital of all civilized nations is embarked — and 
probably two hundred millions of men expend their daily toil — that art 
must confessedly be the most important of all ; the parent and precursor 
of all other arts. In every country then, and at every period, the in- 
vestigation of the principles on which the rational practice of this art is 
founded, ought to have commanded the principal attention of the great- 
est minds. To what other object could they have been more benefi- 
cially directed ? 

But there are periods in the history of every country when the study 
of Agriculture becomes more urgent, and in that country acquires a 
vastly superior importance. When a tract of land is thinly peopled, 
like the newly settled districts of North America, New Holland, or 
New Zealand, a very defective system of culture will produce food 
enough not only for the wants of the inhabitants, but for the partial sup- 
ply of other countries also. But when the population becomes more 
dense, the same imperfect or sluggish system will no longer suffice. 
The land must be better tilled, its special qualities and defects must be 
studied, and means must gradually be adopted for extracting the maxi- 
mum produce from every portion susceptible of cultivation. 

The British islands are in this latter condition. Agriculture now is 
of vastly more importance to us as a nation, than it was towards the 
close even of the last century. In 1780, the island of Great Britain 
contained about 9 millions of inhabitants ; it now contains nearly 20. 
The land has not increased in quantity, but the consumption of food has 
probably more than doubled. The importation from abroad has not in- 
creased to any important extent ; by improved management, therefore, 
the same area of land has been caused to yield a double produce. 

But the population will continue to increase; can we expect that the 
food raised from the land will continue to increase in the same ratio? 



i2 ON IMPROVEMENTS IN AGRICULTURE. 

This is an important question, to which we can give only an imperfect 
and somewhat unsatisfactory answer. 

The superficial area of Great Britain comprises about 57 millions of 
acres, of which 34 millions are in cultivation, about 13 millions are in- 
capable of culture, and the remaining 10 millions are wastelands suscep- 
tible of improvement. The present population, therefore, is supported 
by the produce of 34 millions of acres, or every 34 acres raises food for 
about 20 people. Suppose the 10 millions of acres which are suscepti- 
ble of improvement to be brought into such a state of culture as to 
maintain an equal proportion — the most favourable supposition — they 
would raise food for an additional population of about 6 millions, or 
would keep Great Britain independent of any large and constant foreign 
supply till the number of its inhabitants amounted to 26 millions. 
But at the present rate of increase this will take place in about 20 
years,* so that by 1860, unless some general improvement take place 
in the agriculture of the country, the demands of the population will 
have completely overtaken the productive powers of the land. 

But though we cannot say how far the fertility of the soil may be in- 
creased, or how long it may be able to keep a-head of the growing 
numbers of the people, we have our own past experience, the example 
of other countries, and the indications of theory, all concurring to per- 
suade us that the limit of its productive powers can neither be predicted 
nor foreseen. 

If we glance at the history of British agriculture during the last half 
century — from the introduction of the green crop system or the alternate 
iusbandry from Flanders into Norfolk, up to the present time — we find 
the results of each successive improvement more remarkable than the 
former. The use of lime, a more general drainage of the soil, the in- 
vention of improved ploughs and other agricultural implements, as well 
as the introduction of better and more economical modes of using them, 
the application of bone manure, and more recently of thorough draining 
and subsoil ploughing, have all tended not only to the raising of crops 
at a less cost, but in far greater abundance, and on spots which our 
forefathers considered wholly unfit for the growth of corn. 

The result of each new improvement, I have said, has seemed more 
astonishing than the former. For after a waste piece of land has been 
brought into an average state of productiveness, we are not prepared for 
any great improvement upon it by new labours ; nor could we readily 
believe that, half a century after such land had been in culture, its pro- 
duce or its value should at once be doubled, by a better draining, a 
deeper ploughing, or by sprinkling on its surface a small quantity of a 
saline substance imported from a foreign country. 

Yet the example of the Chinese shows us that the productive powers 
of the soil are not to be easily estimated. Nothing repays the labours 
of the husbandman more fully than the willing soil — nothing is more 
grateful for his attention, or offers surer rewards to patient industry, or 
to renewed attempts at improvement. 

In China we see a people whom we call semi-barbarians, multiply- 
ing within their own limits till their numbers are almost incredible; 

" For more precise data and calculations see Porter's Progress of the Nation. 



PROSPECTS OF SCIENTIFIC AGRICULTURE. 13 

practising from the most remote ages, and in the most skilful manner, 
various arts which the progress of modern science has but recently in- 
troduced into civilized Europe; cultivating their soil with the most assid- 
uous labour, and stimulating its fertility by means which we have hith- 
erto neglected, despised, or been wholly ignorant of — but which the dis- 
coveries of the present time are pointing out as best fitted to secure the 
amplest harvests — and have thus been enabled to compel their limited 
soil to yield a sufficient sustenance to its ainriost unlimited population.* 

Experience and example, therefore, encourage us to look forward to 
still further improvements in the art of culture, and, independent of such 
as may be derived from purely mechanical principles, theoretical 
chemistry seems to point out the direction in which important advances 
of another kind may reasonably be anticipated. The Chinese are said 
to be not only familiar with the relative value and efficiency of the va- 
rious manures, but also to understand how to prepare and apply without 
loss that which is best fitted to stimulate and support each kind of plant. 
How far this statement is exaggerated we are unable at present to de- 
termine, but it is in this direction that chemistry appears likely to pro- 
mote the advance of European agriculture. The practical farmer al- 
ready rejoices in having in one ton of bone dust the equivalent of 14 
tons of farm-j^ard manure; some of the most skilful living chemists 
predict that methods will hereafter be discovered for compressing into a 
still less bulky form the substances required by plants, and that we 
shall live to see extensive manufactories established for the preparation 
of these condensed manures.f 

* An intelligent correspondent reminds me that the agricultural skill of the Chinese is 
questioned by recent writers on the customs of that country. This doubt is founded chiefly 
on the rudeness of their astricultural implements and the scarcity of cattle, whether horses 
or cows, among them. But in this densely peopled country the hoe they employ serves 
the purpose of every other implement (Davis's China, ii. 282), and vyhere the place of cat- 
tle is supplied by an equivalent number of men, there can be no comparative want of 
valuable manure. The population of China, however, is probably not so dense in all the 
provinces as it has hitherto been supposed. Many writers have estimated the entire 

Eopulation at 300 millions, while recent statists reduce it to 175 millions. Taking even the 
igher estimate, the population is not more dense than in England and Holland — the area 
of China proper being 1,200,000 square miles, or eight times that of France. It is considera- 
bly less dense, indeed, if we take into account the number of horses and cattle which in 
Europe are reared and fed on the produce of the land. We may hereafter expect more ac- 
curate information, however, especially regarding the interior of this interesting country. — 
JSee Appendix A. 

t Should the opinions above expressed appear too sanguine to some, or be treated by any 
of my readers as merely theoretical, I would refer them to the words of Mr. Smith of Dean- 
Bton, the inventor of the subsoil plough, and the introducer of the greatest practical im- 
provement in modern agriculture. After stating that at least threefourth-t of the ichole ara- 
ble land in the country is under very indifferent culture, chiefly from the want of complete 
draining and deep working, and, adverting to the increased produce it may be made to 
yield, he says, ■' it is not at all improbable that Britain may become an exporting country in 
grain in the course of the next rwenty years." — Remarks on Thorough Draining and Deep 
Ploughing, by James Smith, Esq., of Deanston Works, p. 22. Were the population to 
. remain stationary, Mr. Smith maybe right; at all events, this opinion shows that even 
practical men do not despair of attaining to a pitch of improvement in agriculture which 
theoretical writers dare not venture to predict. 

But among all persons of enlarged information a similar opinion prevails. Thus the 
eloquent author of a recent work on the principles of population says, " the single alteration 
of substituting the kitchen-garden husbandry of Flanders in our plains, and the terraced 
culture of Tuscany in our hflls, for the present system of agricultural management, would 
at once double the produce of the British islands, and procure ample subsistence for twice 
the number of its present inhabitants." — Alison'^ Principles of Population, I. p. 216. These 
hopes are not to be rejected or suppressed ; for, though they may never be fully realized, 
yet they are, as it were, the seeds of exertion, from which ample harvests of good may 
pcreafter b^ reaped. 

2 



14 NEGLECT OP SCIENTIFIC AGRICULTURE 15 SCHOOLS. 

Thus much may be said in regard to die future hopes and prospects 
of scientific agriculture.* But how few practical men are acquainted 
with what is already known of the principles of the important art by 
which they live! Trained up in ancient methods — attached generally 
to conservaiive principles in every shape — the practical agriculturists, 
as a body, have always been more opposed to change than any other 
large cla"ss of the community. They have been slow to believe in the 
superiority of any methods of culture which differed from their own, 
from those of their fathers, or of the district in which they live— and, 
even when the superiority could no longer be denied, ihey have been 
almost as slow to adopt them. 

But the awakening spirit of the time is making itself felt in the re- 
motest agricultural districts ; old prejudices are dying out, and the cul- 
tivators of this most ancient, most important, and noblest of all the artSj 
are becoming generally anxious for information, and eager for improve^ 
ment.f 

Two circumstances have contributed to retard the approach of this 
better state of things. 

In the first yjlace, the agricultural interest in England has hitliertt 
expended its main strength in attempting to secure or maintain impor-- 
tant political advantages in the state. The encouragement of experi- 
mental agriculture has been in general neglected, while the dilfusion 
of practical knowledge has been either wholly overlooked or considered 
subordinate to other objects. No national efibrts have been made for 
the general improvement of the methods of culture. While for the 
other important classes of the community special sciiools have been es- 
tablished, in which the elements of all the branches of knowledge most 
necessary for each class have been more or less completely taught, and 
a more enlightened, because better instructed, race of men gradually 
trained up, no such schools have been instituted for the benefit of the 
agriculturist. In our Universities, in which the holders of land, those 
most interested in its improvement, are nearly all educated, a lesson 
upon agriculture, the right arm of the Stale, has hitherto scarcely ever 
been given. t With tlie practice of the art, the theory has also been 

Those who have access to the Journal of the Royal English Affricultural Society will 
find in the first number a paper by Mr. Pusey, "On the present state of the science of Agri- 
culture in England," in which much valuable information is contained, and of a more prac- 
tical kind than I have been able to introduce. This paper ought to be printed in a separate 
form, and circulated widely among those who are not members of the Royal English Agri- 
cultural Society. 

t This opinion has been confirmed by the ntimerous communications I have received 
from all parts of the country since the publication of these Lectures was announced, and in 
which I am assured that the want of knowledge is generally felt, and a supply in a sufficient- 
ly elementary form desired, by all classes of ajriciilturists. I conclude, therefore, that Lie- 
big means the following sentence to apply to his German countrymen : " What can be ex- 
pected from the present (generation of) farmers, which recoils with seeming distrust and 
aversion from all the means of assistance offered it by chemistry, and which does not un- 
derstand the art of making a rational application of chemical discoveries." I do not think 
chemists ought in fairness to blame the practical asrriculturists for not understanding the 
art of applying chemical discoveries to the improvement of the culture of the land. They 
must first know what the discoveries are ; and the error has hitherto been, that no stena 
have been taken to ditTuse this preliminary knowledge. 

J However satisfied young men may be to avoid the labor of additional study while at 
College, how many in after-life regret that their early attention had not been directed to 
some of those branches of knowledge which are applicable to common life. Thus the late 
Lord Dudley, in his letters to the Bishop of Llandaff, invariably laments, "as mistakes in 



ENCOURAGEMENT OF AGRICULTURAL LITERATURE. 15 

neglected. Scientific men have had no inducement to devote their 
time and talents to a subject which liejd out no promise of reward, 
either in the shape of actual emolument or of honorary distinction. 
And thus has arisen the second of those circumstances, by which I con- 
sider the approach of a better state of things to have been retarded— 
namely, the want of an Agricultural Literature. 

With the exception of a small number of periodical publications, 
none of these even too well supported, by which attempts have been 
zealously made to diffuse important information among the practical 
farmers — it cannot be denied that the press has not been encouraged to 
do its utmost on behalf of agricultural knowledge in general — while the 
single work of Sir Humjihry Davy is nearly all that chemical science 
has, in this country, been induced to contribute to the advancement of 
agricultural theory during the last forty years.* 

Many of you have probably read this work of Sir Humphry Davy, 
and are prepared to acknowledge its value. Yet how many tilings 
does he pass over entirely, how many things leave unexplained ! Since 
his time, not only have numerous practical observations and discoveries 
been made, but the entire science of animal and vegetable chemistry 
has been regenerated. We are not, therefore, to expect in his work a 
view of the present state, either of our theoretical knowledge, or of our 
practical agriculture. It belongs rather to the history of the progress of 
knowledge, than to the condition of existing information. Hence the 
merits of the agricultural chemistry of Davy are not to be tried by its 
accordance with actual knowledge, but with what was known in 1812, 
when its distinguished author read his course of lectures for the last 
time before the Board of Agriculture. 

We may with certainty predict, however, that neither the practice 
nor the theory of agriculture will be permitted to experience in future 
that want of general encouragement under which during the last half 

Ms early life, his unacqnaintance with the rudiments of ao;ricnlture — his ignorance of bota- 
ny and geology."— (See also a note to the Review of these Letters in the Quarterly Review 
for December, 1S40.) 

For this state of tilings we shall soon have at least a partial remedy. It is a remarkable 
fact that nearly all the new educational instituiions of ihe higher class, on the Continent of 
Europe, of which so many have been founded within the present century, and all those 
which have been established in America, I believe, without exception, have incorporated 
into their course of general study one or more of the newer sciences. Can we have a more 
consentaneous and universal testimony to their value and importance than this? The Uni- 
versity of London has been induced, by the same public demand for this sfiecies of instruc- 
tion, to include Chemistry and Botany in its course of arts; and circumstances only have 
caused Geology to be omitted for a time. Its numerous affiliated institutions have followed 
its steps; and hence the Catholic College of Si;. Cuthbert, at Ushaw, has in this respect an- 
ticipated its Protestant neighbor at Durham. 

But should the agricultural interest rest satisfied with this introduction of one or two 
branches, suppose it generally done, into the University course of study? Many are of 
opinion that it ought not, and that the general interests of practical agriculture would be 
manifestly promoted, among other means, by the establishment of agricultural colleges, in 
which all the branches necessary to be known by enlightened agricultuilsts of every class 
should be specially and distinctly taught. Wliether such Colleges might be beneficially 
annexed to tlie existing Universities, is a question deserving of serious consideration. 

* The latest edition of Lord Dundonald's "Treatise on the intimate connection between 
Chemistry and Agriculture," which I have seen, is dated London, 1803. 

I should be doing injustice to a good chemist and a zealous agriculturist, were I not to 
direct the attention of my readers to a series of excellent articlf^s on chemical agriculture 
by Dr. Madden, inserted in the numbers of the Quarterly Journal of Agriculture for the last 
two years. 

Since the above went to press, Three Lectures on Agriculture have appeared from tho 
pen of Dr. Daubeny, of Oxford, whose name will secure them an extended circulation. 



16 GENERAL SCIENCE AND AGRICULTURE. 

century they have in England been permitted to languish. The public 
mind has been awakened, and tlie establishment of Agricnllural Associ- 
ations, provincial and local, are manilestaiions of the interest nov/ felt 
upon the subject in all parts of the country. It requires only the general 
exhibition of such an interest, and the adoption of sonje general means of 
encouragetiient, to stimulate both practical ingenuity and scientific zeal 
to expend themselves on this most valuable branch of national industry. 

Science is never unwilling to lend her hand to the practical arts; on 
the contrary, she is ever forward to proffer her assistance, and it is not 
till her advances have been rejected or frequently repulsed, that she re- 
frains from aiding in their advancement. 

Need I advert, in proof of this, to the unwearied labours of the vege- 
table physiologists — or to the many valuable observations and experi- 
ments recorded in the memoirs of scientific chemists. In these memoirs, 
or in professedly scientific works, such observations have not unlre- 
quently been permitted to rest; — the public mind being unprepared 
either to appreciate their value or to encourage the exertions of those wko 
were willing to give them a practical and popular form. 

And how numerous are the branches of science connected with this 
art? Need I speak of botany, which is, as it were, the foundation on 
which the first elements of agriculture rest; or of vegetable physiology, 
to the indications of which it has hitherto almost exclusively looked for 
imjjrovement and increased success ; or of zoology, which alone can 
throw light on the nature of the numerous insects that prey upon your 
crops, and so often ruin your hopes, — and which can alone be rea'son- 
ably expected to arm you against their ravages, and instruct you to ex- 
tirpate them ? Meteorology among her other labours tabulates the highest, 
the mean, and the lowest, temperatures, as well as tlie quantity of rain 
which falls during each day and each month of the year. Do you 
doubt the importance of such knowledge to the proper cultivation of the 
land ? Consider the destructive efl!ects of a late frost in spring, or of a 
continued heat in summer, and your doubts will be shaken. A^ wet sea- 
son in our climate brings with it many evils to the practical agriculturist ; 
but what eflfect must the rain have on the soil, in countries where nearly 
as much falls in a month, as in England during the course of a whole 
year ;*— where every thing soluble is speedily washed from the land, and 
nothmg seems to be left but a mixture of sand and gravel ? It may 
indeed be said with truth, that no department of natural science is inca- 
pable of yielding instruction— that scarcely any knowledge is superflu- 
ous — to the tiller of the soil. 

It is thus that all branches of human knowledge are bound together, 
and all the arts of life, and all the cultivators of them, mutually de- 
pendent. And it is by lending each a helping hand to the others, that 
the success of all is to be secured and accelera"ted ; while with the gene- 
ral progress of the whole the advance of each individual is made sure. 

The recent contributions and suggestions of geology are the best proof 
of the readiness of the sciences of observation to give their aid to thej 
promotion especially of agricultural knowledge. The geologist can] 
best explain the immediate origin of your several soils, the cause of the] 

• At Canton, in the month of May. the fall of rain is often as much as 20 Inches. 



r 



GEOLOGY CONNECTED WITH AGRICULTURE. 17 



diversities which even in the same farm, it may be in the same field, 
they not unfreqaently exhibit;* the nature and differences among your 
subsoils, and the advantages you may expect from breaking them up or 
bringing them to the surface. 

Geology is essentially a popular science, and the talents of its emi- 
nent English cultivators are admirably fitted to make it still more so. 
Hence, a certain amount of knowledge of this science has been of late 
years very generally diffused, and its relations to agriculture are be- 
coming every day better understood. The Highland Society of Scot- 
land, among its many other useful exertions, has done very much to 
connect agriculture and geology with the sphere of its own labours, 
while the Journal of the Royat Agricultural Society of England mani- 
fests a similar desire on the part of that numerous and talented body, to 
illustrate the connection of agricuhure with geology and chemistry, in 
the southern division of the island. That Dr. Buckland, Mr. Murchi- 
6on, and Mr. De laBeche have each engaged to make a gratuitous sur- 
vey of the subsoils in several extensive agricultural districts, at the re- 
quest of the Council of this Society,f shows that, where their services are 
estimated, our most eminent scientific men will not hesitate to devote them 
to the development of the most important branches of national industry. 

The time, therefore, is peculiarly favourable for the increase and diffu- 
sion of agricultural knowledge. The growth of our population re- 
quires it — practical men are anxious to receive instruction — scientific 
men are eager to impart what they know, and to make new researches 
for the purpose of clearing up what is unknown — are we not justified, 
therefore, in anticipating hereafter a constant and general diffusion of 
light, a steady progress of agricultural improvement ? ^ ^ 

Having thus glanced at the state and prospects of scientific agricul- 
ture in general, and especially of the art of culture in England, permit 
me to advert to a few of those questions of daily occurrence among you, 
to which chemistry alone can give a satisfactory answer. I shall not in 
this place allude to the subject of manures — which form alone an entire 
chapter of most recondite chemistry, and which I shall take up in its 
proper place, but I shall select a few isolated topics, the bearing of 
chemical knowledge upon which is sufficiently striking. 

Some soils are naturally barren, but how few of our agriculturists are 
able, in regard to such soils generally, to say why ; how few who pos- 
• sess the knowledge requisite for discovering the cause ! Of these bar- 
ren lands some may be improved so as amply to repay the outlay : some, 
from their locality or from other causes, are in the present state of our 
I knowledge irreclaimable. How important to be able to distinguish be- 
f tween these two cases ! 

* I cannot refer to a plainer, more simple, or more beanfiful illustration of this fact than 
' that which is presented in a short paper by Sir John Johnstone, Bart., inserted in the Jour- 
I nal of the Enyilish Agricultural Society, I. p. 271, entitled "On the Application of Geology to 
Agriculture."" See also an able paper by the Rev. Mr. Thorpe, of which a valuable report is 
contained in the Doncasfer Chronicle of December 5th, and which will be published in the 
1 proceedings of the Geological and Polytechnic Society of the West Riding of Yorkshire, 
t Journal of the Royal Agric.ultural Society, Report of their Council, 1. p. 188. 
To form a just idea of the value and importance of such surveys, it is only necessary to 
read chap, xv., pp. 463 to 480, of Mr. De la Beche's "Geological Report on Cornwall and De- 
von," or Professor Hitchcock's "Report on a re- examination of the Economic Geology of 
1 Massachusetts." 

2* 



18 CHEMISTRY AND AGRICULTURE. 

Some apparently good soils are yet barren in a high degree. In en- 
deavouring to improve such soils, practical men have no general rule — 
ihey can have none. They work in the dark — like a man who makes 
experiments in a laboratory, without a teacher or without a book, till, < 
after many blunders and much expense, he discovers some fact, to him- 
self new, but to others long known, and forming only one of many ana- 
logous facts, flowing from a common, and probably well understood, 
principle. 

" The application of chemical tests to such a soil," says Sir Humphry 
Davy, " is obvious. It must contain some noxious principle, [or be de- 
ficient in some necessary element. — J.] which may be easily discovered 
and probably easily destroyed. Are any of the salts of iron present, 
ihey may be decomposed by lime. Is there an excess of siliceous sand, 
the system of improvement must depend on the application of clay and 
calcareous matters. Is there a defect of calcareous matter, the remedy 
is obvious. Is an excess of vegetable matter indicated, it may be re- 
moved by liming, paring, and burning. Is there a deficiency of vege- 
table matter, it is to be supplied by manure." — [Agricultural Chemistry, 
Lecture I.] 

What was true in regard to the applications of chemistry in the time || 
of Sir Humphry Davy is more true in a high degree of the chemistry 7' 
of our time. Not only is the nature of soils better understood, but we 
know in many cases what a soil must contain before it will produce a 
given crop. Why do pine forests settle themselves on the naked and 
apparently barren rocks of Scotland and of Northern Europe, content if 
their young roots can find but a crevice in the mountain to shelter them» ? 
Why does the beech luxuriate in the alluvial soils of Southern Sweden, 
of Zealand, and Continental Denmark ? Why does the birch spring 
up from the ashes of the pine forest — why the rapid rush of delicate 
grass from the burned prairies of India and of Northern America? 
Whence comes the thick and tender sward of the mountain limestone 
districts — whence the gigantic wheat stalk of a virgin soil ? Why do 
the same forest trees propagate themselves for ages on the same spots 
without impoverishing the soil — why do the natural grasses, the longer 
they are undisturbed, render the land only the more fertile ? 

These, one would think, are scarcely chemical questions, and yet to 
all of them, and to a thousand such, chemistry alone can and will give 
a satisfactory answer. 

The rotation of crops is a practical rule, the benefit of which has 
been proved by experience ; it becomes a true philosophical principle 
of action, when we discover the causes from which this benefit springs. 
Botany has thrown considerable light, and of an interesting and impor- . 
tant kind, upon this practice, but chemistry has fully cleared it up and 1 
established the principle. }. 

Sir Humphry Davy speaks of the use of lime. Can you explain the 
mysterious, and apparently fickle and diversified, agency of this sub- 
stance in reference to vegetation? Are the advantages so frequently 
attendant upon its use to be ascribed to the chemical character of the 
soil to which it is applied, to the kind and quantity of the vegetable 
matter it contains, or to the geological nature of the rocks on w4iich it 
rests? Are they dependent upon the drainage and exposure of the 



THEORETICAL KNOWLEDGE STILL VERY DEFECTIVE. 19 

land — on the kind of crop to be raised — on the general climate of the 
district — on the maxima and minima of temperature — or on the quanti- 
ty of rain which falls? 

80 with gypsum. Why are its effects lauded in one district, doubted 
in another, and decried in a third! Are no rules or principles to be 
discovered, by which these diversified effects are to be explained, and 
the true ptirpose and fit use of these and other mineral substances clear- 
ly pointed out? Such principles are yet to be sought for; but if 
sought by the way of well devised and accurately conducted experi- 
ment, they are sure to be discovered. 

The land is exhausted by frequent cropping. What language more 
famiUar, what statement more true than this? Yet how few under- 
stand what exhaustion implies; how few can explain either how it 
takes place, by what means it can be remedied, or how, if left to her- 
self, nature at length does apply a remedy ! 

Have you any doubt in regard to the prevailing ignorance on this 
subject ? To be satisfied, you have only to look with an experienced 
eye on the agricultural practice of the county of Durham. Are there 
not thousands of acres in the centre of this county which exhibit a de- 
gree of unproductiveness not natural to the soil ; — which have been 
overcropped, and worn out, and impoverished? A soil comparative- 
ly fertile by nature has been rendered unfertile by art. That which 
was naturally good has been rendered as unproductive and unprofitable 
as that which was naturally bad. Has this state of things arisen from 
ignorance, from design, or from necessity ? By whichever of these it 
has been immediately caused, it is clear that the requisite degree of 
knowledge on the part of the owners of the soil would have retarded if 
not wholly prevented it. 

The same knowledge will enable them to reclaim these lands again, 
and gradually restore them to a more fertile condition ; for the changes 
which the soil undergoes in such circumstances are all chemical 
changes, — either in the relative quantities of the substances it contains, 
or in the state of combination in which they exist. 

The art of culture indeed is almost entirely a chemical art, since 
nearly all its processes are to be explained only on chemical principles. 
If you add lime or gypsum to your land, you introduce new chemical 
agents. If you irrigate 3'^our meadows, you must demand a reason 
from the chemist for the abundant growth of grass which follows. Do 
'you find animal manure powerful in its action, is the effect of some 
permanent, while that of others is speedily exhausted ? — does a mixture 
of animal and vegetable manure prepare the land best for certain kinds 
of grain? — do you employ common salt, or gypsum, or saltpetre, or ni- 
trate of "Soda, with advantage ? — in all these cases you observe chemical 
results which you would be able to control and modify did you possess 
the requisite chemical knowledge. 

It is not wonderful that even theoretical agriculturists should be far 
behind in the knowledge of those principles on which their most impor- 
tant operations depend. The greatest light has been thrown upon the 
art of culture by the researches of organic chemistry, a branch which 
may be said to have started, if not into existence, at least into a new 
life, within the last ten years. Every day too is adding to the number 



^i 



20 OUTLINE or THE COURSE OF LECTURES. 



and value of its discoveries, and the agriculturist may well be pardoned 
for not keejnng pace with the advances of a department of science, 
Avluch even the pn^fessed and devoted chemist can scarcely overtake. 

I miijht advert also to the mechanical operations of y>loughing, wheth- 
er common or subsoil, of fallowing, draining, weeding, and many 
others, as being only so many methods by which chemical action is in- 
duced or facilitated ; — to the growth of plants, and even to such ob- 
served diflerences as that of the relative quantity of leaves and tubers in 
the potatoe, and of grain and straw in our corn-fields, as interesting 
cases on which scientific chemistry throws a flood of light. I might 
shew how the feeding of your cattle and the raising and management 
of dairy produce are not beyond the province of chemistry, but that the 
only approach to scientific principle yet made, even in these branches 
of husbandry, is derived from the results of chemical research. 

But I do not dwell on any of these }X)ints: they will all hereafter 
come under our review in their appropriate order, and will aff()rd me an 
opportunity of laying before you many im[)ortant facts, as well as, I 
hope, valuable practical deductions and observations. 

While, however, I feel justified in saying thus much of the light 
which existing chemical knowledge throws on the natural processes of 
vegetation, and on the artificial methods of practical agriculture, I 
would not lead you to supy)Ose that our knowledge is by any means 
complete, that there are not many points over which much darkness 
still rests — that some of the theoretical views now entertained are not 
crude, adopted too hastily, and generalized too rapidly. But a similar 
confession may be made in reference to all the modern sciences of ob- 
servation without diminishing their importance or detracting from the 
value of the facts they embody. Human science is progressive in all 
its branches, and to refuse to follow the indications of existing know- 
ledge because it is to some extent uncertain, would be as foolish as to 
refuse to avail ourselves of the morning's light, because it is not equal 
to that of the midday sun. 



1 advance, therefore, to the special object of these lectures, and I shall 
first present you with a rapid outline of the inethod which I intend to 
follow. It is indispensable that this method should be simple, and that 
every consecutive portion should be so fitted to clear the way for, and 
throw light upon, what is to follow, that we may be able to advance 
from the first rudimeiits to the most difficult and abstruse parts of our 
subject, without any chance of the illustrations being even difiScult to 
comprehend. This end I do not hope perfectly to attain, but it will be 
my constant aim, and, with due attention on your part, I do not fear 
that we shall fail in arriving at a perfect understanding of the various 
points to which I shall have occasion to direct your attention. 

I propose, therefore, to bring before you — 

I. The constitution of vegetable substances with the properties of the 
elementary and compound bodies which either enter into the substances 
of plants or contribute to their growth and nourishment. 

II. The general structure and functions of the several parts of plants 



ORGANIC AND INORQAXIC BIATTER. 21 

— their inode of growth — and the manner in which their fooa is ab- 
sorbed, changed, and converted into parts of their substance. 

III. The origin, nature, and principal differences of soils — with tho 
circumstances on which their relative fertility depends, or under which 
it is modified. 

IV. The nature and d ifrc re nces of manures, and their mode of action, 
whetfier directly in supplying food to the plant, or indirectly in hasten- 
ing and increasing their growth. 

V. The nature and diversities of the food raised as the result of cul- 
ture — especially in reference to their several equivalents or powers of 
supporting animal life. 

Under this head the feeding of cattle and the variations in the quan- 
tity and quality of dairy produce, will form subjects of consideration; 

These different branches, I believe, comprehend the whole subject 
of chemical agriculture ; in regard to all of them we shall derive either 
from chemistry or geology much important information. 

§ 1. Different kinds and states of matter. 

All the forms of matter which present themselves to our view, 
whether in the solid crust of the globe on which we live, in the air 
which forms the atmosphere by which we are surrounded, or in the bo- 
dies of animals and plants — all are capable of being divided into the two 
great groups of organic and inorganic matter. The solid rocks and soils, 
the atmosphere, the waters of the seas and oceans, every thing which 
neither is nor has been the seat of life, may generally be included under 
the head of inorganic matter. The bodies of all living animals and 
plants, and their dead carcases, consist of organic or organized matter. 
These generally exhibit a kind of structure readily visible by the eye, 
as in the pores of wood, and in the fibres of hemp, or of the lean of 
beef,* and are thus readily distinguished from inorganic matter, in 
which no such structure is observable. 

But in many substances of orsanic origin also, no structure is obser- 
vable. Thus, sugar, starch, and gum, are formed in plants in great 
abundance, and yet do not present any pores or fibres; they have never 
been endowed with organs, yet being produced by the agency of living 
organs, they are included under the general name of organic matter. 
So when animals and plants die, their bodies undergo decay, but the 
matter of which tliey are composed is considered as of organic origin, 
not only as long as any traces of structure are observable, but even after 
all such traces have disappeared. Thus coal is a substance of organic 
origin, though almost all traces of the vegetable matter from which it 
has been derived, have been long ago obliterated. 

Again, heat chars and destroys wood, starch, and gum, forming black 
substances totally unlike the original matter acted upon. By distillation, 
wood yields tar and vinegar; and by fermentation, sugar is converted 
first into alcohol, and then into vinegar. All substances derived from 
vegetable or animal jiroductsby these and similar processes are included 
under the general designation of organic bodies. 

* The pores of woofi and fibres and minute vessels in animals being the organs or instru- 
ments of life, the substances themselves are called organized or organic. 



22 5UMBER or ELEMENTiiRY BODIES. 

Now if we take a portion of almost any of those numerous forms 
of matter which we meet with either in the inorganic or in the organic 
kingdoms, we find, that on subjecting it to certain chemical processes, it 
is capable of being resolved or separated into more than one substance. 
Thus coal when put into a gas retort is resolved into tar, coal gas, and 
certain other substances. Wootl, when treated in the same way, yields 
pyroligneous acid, tar, and water, and leaves behind a residue of char- 
coal. °If again we subject charcoal to the action of heat (not in the 
open air), or (o any other process we can devise, we can never separate 
any thing further from it. After all our operations we obtain only 
charcoal. 

So a piece of common lead ore, when healed in a similar manner, 
will, if pure, give off sulphur only, and leave the lead behind, from which 
nothing but lead can afterwards be extracted. 

Thus it is evident that wood and the ore of lead differ from charcoal 
and metallic lead in this respect, that the former consist of more than one 
kind of matter, the latter of one kind of malter only. Hence charcoal 
and lead are called simple or elementary bodies, while wood and all oth- 
er substances which are capable of being resolved into two or more 
different kinds of matter are called compound bodies. 

The diversified forms of matter which present themselves to our no- ] 
tice in the mineral crust of the globe, and in the organs and vessels of 
plants and animals, are absolutely without number. We can no more 
reckon them than we can the stars of heaven. Yet it is one of those re- 
sults of modern chemistry which to the mind not yet familiarized 
with chemical discoveries appears most wonderful, — that these num- 
berless forms of matter are capable of being resolved into, and there- 
fore are composed or made up of, only 55* of those simple or ele- I 
meritary substances, the nature of which has been above explained. ■ ' 
Occasionally these elementary substances occur in a separate state, as 
in native [so called when found in the malleable state,] gold and silver, 
but they are generally found associated together, forming substances 
from which several of the 55 simple bodies may be extracted. 

All the material substances in nature consist of one or more of these , , 
55 elementary bodies. This is sufficiently surprising, yet it is, if pos- I 
sible, still more remarkable that nearly the entire mass of every vege- 
table substance may be resolved into one or more o^ four only of these 
simple substances. 

When a portion of animal or vegetable matter is burned it either en- 
tirely disappears or leaves behind it only a small quantity of ash. Ani- 
mal and vegetable oils and fats, gum, sugar, and starch, when burned, 
disappear entirely ; a piece of wood or of lean meal leaves a small 
quantity of earthy (inorganic) matter behind. 

Now all that disappears when any portion of vegetable matter, of any 
kind, is burned, consists generally of three, and only in some rare cases 



* The names of these elementary bodies are as follows :— Oxygen, hydrogen, nitrogen, 
sulphur, selenium, phosphorus, chlorine, bromine, iodine, fluorine, carbon, boron, silicon, 
potassium, sodium, lithium, barium, strontium, calcium, magnesium, aluminium, glucinium, 
yttrium, zirconium, thorium, cerium, lanthanium, manganese, iron, cobalt, nickel, zinc, 
cadmium, lead, tin, bismuth, copper, uranium, mercury (quicksilver), silver, palladium, 
iridium, platinum, gold, osmium, titanium, tantalum (columbium), tungsten, mo^'bdenum, 
vanadium, chromium, antimony, tellurium, arsenic. 



i 



PROPEaTIES OF CARBON. 23 

of more than four, of the elementary bodies. These four are carbon, 
oxygen, hydrogen, and nitrogen. With the exception of the matter in- 
destructible by fire (the ash), chemical analysis* has hitherto failed todetect 
the presence, in any notable quantity, of more than these four substances. 
The same remarks apply with almost equal truth to animal substances. 
The destructible part of these also consists of the same four elements. 

To the agriculturist, therefore, an acquaintance with these four con- 
stituent parts of all that lives and grows on the face of the globe is 
indispensable. It is impossible for him to comprehend the laws by 
which the operations of nature in the vegetable kingdom are conducted, 
nor the reason of the processes he himself adopts in order to facilitate or to 
modify these operations, without this previous knowledge of the nature 
of the elements— the raw materials as it were— out of which all the 
products of vegetable growth are elaborated. 

I shall first, therefore, exhibit to you briefly the properties of these 
organic constituents of plants, in order that we may be prepared for the 
further inquiries— by what means or in what form they enter into the cir- 
culation of plants — and how, when they have so entered, they are con- 
verted into those substances of which the skeleton of the plant consists 
or which are produced in its several organs. 

§ 2. Carbon — its properties atid relations to vegetable life. 

Carbon is the name given by chemists to the substance of wood char- 
coal in its purest form. When wood is distilled in close vessels, or 
burned in heaps covered over, so as to prevent the free access of air, 
wood charcoal is left behind. When this process is well performed, the 
charcoal consists of carbon with a slight admixture only of earthy and 
saline matters, which remain behind on burning the charcoal in the air. 

Healed in the air, charcoal burns with little flame, and, with the ex- 
ception of the ash which is left, entirely disappears. It is converted into 
a kind of air known among chemists by the name of carbonic acid, which 
ascends as it is formed and mingles with the atmosphere. 

Charcoal is light and porous, and floats upon water, but plumbago or 
black lead and the diamond, which are only other forms of carbon, are 
heavy and dense. The former is 2^, and the latter 3|, times heavier 
than water. The diamond is the purest form of carbon, and at a high 
temperature it burns in the air or in oxygen gas, and, like charcoal, dis- 
appears in the state of carbonic acid gas. 

Of this carbon all vegetable substances contain a very large portion. 
It forms from 40 to 50 per cent., by weight, of all the parts of plants 
which are cultivated for the food of animals or of man, [that is, of these 
plants in their dried state.] In the economy of nature, therefore, it per- 
forms a most important part. 

The light porous charcoals obtained from wood [especially from the 
willow, the pine, and the box], and from animal substances, possess 
several interesting properties, which are of practical application in the 
art of culture. 1°. They have the power of absorbing in large quanti- 
ty into their pores, the gaseous substances and vapours -which exist in 

• Under the general name of chemical analysis are comprehended the various processes 
by which, as above explained, natural forms of matter may be resolved or separated into 
the several elements or simple substances of which they consist. 



24 PROPERTIES OF OXYGEN. 

the alniosphere ;* and on this properly, as I shall explain hereafter, the 
use of cliarcoal powder as a manure probably in some measure depends. 
2°. They also separate from water any decayed animal matters or col- 
ouring substances which it may hold in solution ; hence its use in filters 
for purifying and sweetening impure river or spring waters, or for clari- 
fying syrups and oils. This action is so powerful that port wine is 
rend'ered perfectly colourless by filtering through a well prepared char- 
coal. 

In or upon the soil charcoal for a time will act in the same manner, 
will absorb from the air moisture and gaseous substances, and from the 
rain and from flowing waters organized matters of various kinds, any 
of which it will be in a condition to yield to the plants which grow 
around it, when they are such as are likely to contribute to their 
growth. 

3°. They have the property also of absorbing disagreeable odours in 
a very remarkable manner. Hence animal food keeps longer sweet 
when placed in contact with charcoal — hence also vegetable substances 
containing much water, such as potatoes, are more completely preserved 
by the aid of a quantity of charcoal — and hence the refuse charcoal of the 
sugar refiners is found to deprive night-soil of its disagreeable odour, and 
to convert it into a dry and portable manure. 4°. They exhibit also 
the still more singular property of extracting from water a portion of the 
saline substances they may happen to hold in solution, and thus allow- 
ing it to escape in a less impure form. The decayed (half carbonized) 
roots of grass, which have been long subjected to irrigation, may act in 
one or all of these ways on the more or less impure water by which 
they are irrigated — and thus gradually arrest and collect the materials 
which are fitted to promote the growth of the coming crop. 

§ 3. Oxygen — its properties and relations to vegetable life. 

Oxygen is a substance with which we are acquainted only in the gas- 
eous or aeriform state. f By the unaided senses it cannot be distin- 
guished from common air, being void of colour, taste and smell. But 
if a lighted taper be plunged into it, the flame is wonderfully increased 
both in size and brilliancy, and the taper burns away with great 
rapidity. 

The effect of this gas upon animal life is of a similar kind. When 
a living animal is introduced into a large vessel filled with oxygen, the 
rapidity of the circulation is increased, all the vital functions are stimu- 
lated and excited, a state of fever comes on, and after a time the ani- 
mal dies. 

By these two characters, oxygen is distinguished from every other ele- 
mentary body. It exists in the atmosphere to the amount of 21 percent, 
of its bulk, and in this state of air is necessary to the existence of ani- 
mals and of plants, and to the support of combustion on the face of the 
globe. ^ It exists also largely in water, every nine pounds of this liquid 
containing eight pounds of ox^'gen. 

• Thus of ammonia they absorb 9u times their own bulk, of sulphuretted hydrogen 55 times, 
of oxygen 9 times, of hydrogen nearly twice their bulk, and of aqueous vapour so much as to 
increase their weight from 10 to 20 per cent. 

t In this state it is readily obtained by healing in a glass retort the red oxide of mercury 
of the shops, or a white salt known by the name of chlorate of potash 



1 



PROPERTIES OF HYDROGE.V. 25 

But the quantity of this substance which is stored up in the solid rocks 
is still more remarkable. Nearly one-half of the weight of tbe solid 
rocks which compose the crust of our globe, of every solid substance we 
see around us — of the houses in which we live, and of the stones on 
which we tread — of the soils which you daily cultivate, and much more 
than one-half by weight of the bodies of all living animals and plants, 
consist of this elementary body oxygen, known to us, as I have already 
said, only in the state of a gas. - It may not apjjcar surprising that any 
one elementary substance should have been formed by the Creator in 
such abundance as to constitute nearly one-half by weight of the entire 
crust of our globe, but it must strike you as remarkable, that this should 
also be the element on the presence of which all animal life depends — 
and as nothing less tlian wonderful, that a substance which we know 
only in the state of thin air, should, by some wonderful mechanism, be 
bound up and imprisoned in such vast stores in the solid mountains of 
the globe, be destined to pervade and refresh all nature in the form of 
water, and to beautify and adorn the earth in the solid parts of animals 
and plants. But all nature is full of similar wonders, and every step 
you advance in the study of the principles of the art by which you live, 
you will not fail to mark the united skill and bounty of the same great 
Contriver. 

Oxygen gas is heavier than common air in the ])roportion of about 11 
to 10 [its specific gravity by experiment is 1*1026, air being 1] ; it is 
also capable of being absorbed by water to a certain extent. One hun- 
dred measures of water dissolve 6h of this gas. [De Saussure. Ac- 
cording to Dr. Henry, 100 volumes of water absorb only 3^ of oxygen.] 
Rain, spring, and river waters, always contain a portion of oxygen 
which they have derived from the atmosphere, and this oxygen, as they 
trickle through the soil, ministers to the growth and nourishment of plants 
in various ways. Some of these will be explained in a subsequent lecture. 

In an atmosphere of pure oxygen gas, plants refuse to vegetate, and 
speedily perish. 

§ 4. Hydrogen — its properties and relations to vegetable life. 

Hydrogen is also known to us only in the state of gas, and when per 
fectly j)ure agrees with oxygen and common air in being without colour, 
taste, or smell. It is not known to occur in nature in a free or simple 
state, nor does it exist so abundantly as either carbon or oxygen. It 
forms a small per centage of the weight of all animal and vegetable 
substances, and constitutes one-ninth of the weight of water, but with 
the exception of coal, it does not enter as a constituent into any of the large 
mineral masses that exist in the crust of the globe. 

When a lighted taper is plunged into this gas it is immediately ex- 
tinguished, but if in contact with the air the gas itself takes fire and burns 
with a pale yellow flame. If previously mixed with air or with oxygen 
gas, it kindles and burns with a loud explosion. During this combuS' 
tion water is formed. [See the Second Lecture.] 

It does not support life, animals cease to breathe when introduced into 
it, and plants gradually wither and die. It is the lightest of all known 
substances, being about 14^ times lighter than common air, so that if the 
stopper be removed from a bottle in which it is contained it almost imme- 



26 PROPERTIES OP MTROGEN. 

diately escapes, [its specific gravity, by experiment, is 0-0687, air be- 
in? 1.] It is the element which is employed to give buoyancy to 
balloons ; and by liiis great levity and its relations to flame it is readily 
distinguished from all other known substances. 

Water absorbs it only in very small quantities, 100 gallons taking up 
no more than about l^ gallons of hydrogen gas. But, as already ob- 
served, this gas does noit exist in nature in a free state — is not necessary, ■{ 
therefore, to the growth of |)lants or animals in this state — and hence its ■ 
insolubility in water is in unison with the general adaptation of every 
property of every body, to the health and growth of the highest orders 
of living beings. 

Hydrogen gas is readily obtained from water by putting into it a few 1: 
pieces of metallic iron or zinc, and adding a little sulphuric acid (oil of f 1 
vitriol). Bubbles of the gas are liberated from the surface of the metal, 
ascend through the water, and may be collected on the surface. 

§ 5. Nitrogen — its properties and relations to vegetable life. 

Nitrogen is also known to us only in the form of gas. It exists in the 
atmosphere to the amount of 79 per cent, of its bulk. It is without K 
colour, taste, or smell. Animals and plants die in this gas, and a taper ■ 
is instantly extinguished when introduced into it ; the gas itself under- 
going no change. It is lighter than atmospheric air, in the proportion 
of 97i to 100, [its density is 0*976, air being 1.] It is an essential 
constituent of the air we breathe, serving to temper the ardour with 
which combustion would proceed and animals live in undiluted oxygen 
gas. It forms a part of very many animal and of some vegetable sub- 
stances, but it is not known to enter into the composition of any of the 
great mineral masses of which the earth's crust is made up. In coal 
alone, which is of vegetable origin, it has been delected to the amount 
of one or two per cent. It is therefore much less abundant in nature 
than any of the other so called organic elements — and it exhibits much 
less decided properties than any of them ; yet we shall hereafter see 
that it performs certain most important functions in reference both to the 
growth of plants and to the nourishment of animals. 

One hundred volumes of water dissolve about li volumes of this 
gas.* Spring and rain waters absorb it as they do oxygen, from the at- 
mospheric air, and bear it in solution to the roots, by which it is not un- 
likely that it may be conveyed directly into the circulation of plants. 



I 



Such are the several elementary bodies of which the organic or de- 
utructible part of vegetable substances is formed. With one exception 
they are known to us only in the form of gases; and yet out of these 
gases much of the solid parts of animals and of plants are made up. 
When alone, at the ordinary temperature of the atmosphere they form 
invisible kinds of air ; when united, they constitute those various forms 
of vegetable matter which it is the aim and end of the art of culture to 
raise with rapidity, with certainty, and in abundance. How difficult 
to understand the intricate processes by which nature works up these 

* Henry De Saussure says, that pure water absorbs 4 per cent, of its bulk of this gas. 



REWARDS OF STUDT. 27 

raw materials into her many beautiful productions — yet how interest- 
ing it must be to know her ways, how useful even partially to find them 
out ! 



Permit me, in conclusion, to submit to you one reflection. We have 
seen that oxygen, hydrogen, and nitrogen, are all gaseous substances, 
which when "pure are destitute of colour, taste, and smell. They can- 
not be distinguished by the aid of our senses. Man in a state of nature 
—uneducated man — cannot discern that they are different. Yet so 
simple an instrument as a lighted taper at once shows them to be totally 
unlike each other. This simple instrument, therefore, serves us in- 
stead of a new sense, and makes us acquainted with properties the ex- 
istence of which, without such aid, we should not even have suspected. 
Has the Deity then been unkind to man, or stinted in his benevolence 
in withholding the gift of such a sense ? On the contrary, he has given 
us an understanding which when cultivated is better than twenty new 
senses. The cherriist in his laboratory is better armed for the investi- 
gation of nature, than if his organs of sense had been many times mul- 
tiplied. He has many instruments at his command, each of which, 
like the taper, tells him of properties which neither his senses nor any 
other of his instruments can discover ; and the further his researches 
are carried, the more willing does nature seem to reveal her secrets to 
him, and the more rapidly do his chemical senses increase. Do you 
think that the rewards of study and patient experimental research are 
confined to the laboratory of the chemist, and that the Deity will prove 
less kind to you, whose daily toil is in the great laboratory of nature 1 
As yet you see but faintly tne reason of many of your commonest oper- 
ations, and over the results you have comparatively little control — but 
the light is ready to spring up, the means are within your reach — you 
have only to employ your minds as diligently as you labour with your 
hands, and ultimate success is sure. 



LECTURE II. 

Charactoristlc properties of orsranic substances— Relative proportions of organic elements — 
Variable proportions of inor-^anic elements in plants— Form in which the organic eie 
ments are taken up by plants- The atmosphere, its constitution and relations to vegetablo 
life— Nature and laws of chemical combination- Water and its relations to vegetable life 

§ 1. Characteristic jiroper ties of organic substances. 

Of the four elementary substances described in ihe former lecture, the 
organic parr of all animal and vegetable substances consists. What is 
understood by the term organic has also been explained. 

But organic substances pos>.ess certain characters by which they are 
distinguished from the morganic or dead matter of the globe, and on 
which their connection with the principle of life, and with the art of 
culture, entirely depends. These characteristic properties are chiefly 
the following : 

1°. They are all easily decomposed or destroyed by a moderately 
high temperature. If wood or straw be heated in the air, as over the 
flame of a candle, it becomes charred, burns, and is in a great measure 
dissipated. So sugar and starch darken in colour when heated, black- 
en, and lake fire. The same is true of all vegetable substances. But 
limestone, clay, and other earthy or stony matters, undergo no appar- 
ent change in such circumstances — they are not decomposed. 

2°. When exposed to the air, especially if it be warm and moist, 
vegetable and animal substances putrify and decay.* They decom- 
pose of their own accord, and after a time almost entirely disappear. 
Such is not the case with inorganic matters. If the rocks and stones 
crumble, their particles may be washed away by the rains to a lower 
level, but they never putrify or wholly disappear. 

3°. They consist almost entirely of two or more of the four organic 
elements only. The mineral substances we meet with on the earth's 
surface, and collect for our cabinets, often contain portions of manv ele- 
mentary bodies; but, with few exceptions, the organic part of all plants, 
that which lives and grows, contains only the four simple substances 
described in my former lecture. 

4°. They are distinguished also by this important character, that 
they cantiot be formed by human art. Many of the inorganic com- 
pounds which occur in the mineral crust of the 'globe can be produced by 
the chemist in his laboratory, and were any corresponding benefit likely 
to be derived from the expenditure of time and labour, there is reason to 
believe that, with a few exceptions, nature might be imitated in the for- 
mation of any of her mineral productions. But in regard to organic sub- 
stances, whether animal or vegetable, the chemist is perfectly at fault. 
He can form neither woody fibre, nor sugar, nor starch, nor muscular 
hbre, nor any of those substances which constitute the chief bulk of ani- 
mals and plants, and which serve for the food of animated beings. 



PROSPECTS OF SCIENCE. 29 

This is an important and striking, and is, I believe, likely to remain a 
permanent distinction, between most substances of organic and of inor- 
ganic origin. 

Looking back at the vast strides which organic chemistry has made 
wiiliin the last twenty years, and is still continuing to make, and trust- 
ing to the continued progress of human discovery, some sanguine chem- 
ists venture to anticipate the time when the art of man shall not only 
acquire a dominion over that principle of life, by the agency of which 
plants now grow and alone produce food for man anri beast, but shall be 
able also, in many cases, to imitate or dispense with the operations of thai 
principle: and to predict that the time will come when man shall man- 
ufacture by art those necessaries and luxuries for which he is now wholly 
dependent on the vegetable kingdom. 

And, having conquered the winds and the waves by the agency 
of steam, is man really destined to gain a victory over the uncertain sea- 
sons too? Shall he come at last to tread the soil beneath liis feet as a 
really useless thing — to disregard the genial shower, to despise the influ- 
ence of the balmy dew — to be indifferent alike to rain and drought, to 
cloud and to sunshine — to laugh at the thousand cares of the husband- 
man — to pity the useless toil and the sleepless anxieties of the ancient 
tillers of the soil ? Is the order of nature, through all past time, to be re- 
versed — are the entire constitution of society, and the habits and pur- 
suits of the whole human race, to be completely altered by the pro- 
gress of scientific knowledge? 

By placing before man so many incitements to the pursuit of know- 
ledge, the will of the Deity is ,that out of this increase of wisdom he 
should extract the means of increased happiness and enjoyment also. 
But set man free from the necessity of tilling the earth by the sweat of 
his brow, and you take from him at the same time the calm and tran- 
quil pleasures of a country life — the innocent enjoyments of the return- 
ing seasons — the cheerful health and happiness that wait upon labour 
in the free air and beneath the bright sun of heaven. And for what? — 
only to imprison him in manufactories, to condemn him to the fretful 
and feverish life of crowded cities. 

To such ends, I trust, science is not destined to lead ; and he is not 
only unreasonably, but thoughtlessly sanguine," who would hope to de- 
rive from organic chemistry such power over dead matter as to be able 
to fashion it into food for living animals. With such consequences be- 
fore us it seems almost sinful to wish for it. 

Yet, that this branch of science will lead to great ameliorations in the 
art of culture, there is every reason to believe. It will explain old meth- 
ods — it will clear up anomalies, reconcile contradictory results by ex- 
plaining the principles from which they flow — and will suggest new meth- 
ods by which better, speedier, or more certain harvests ihay be reaped. 

§ 2. Relative proportions of organic elements. 
Though the substance of plants consists chiefly of the four organic ele- 
ments, yet these bodies enter into the constitution of vegetables in very 
ditferent proportions. This fact has already been adverted to in a gen- 
eral manner: it will appear more distinctly by the following statement 
of ihe exact quantities of each element contained in 1000 parts by 



Hay from 

young Clover 

3 mos. old. 


Oats. 


Clover- 
Seed. 


A.ftcr-math 
Hay. 


Peas. 


Wheat. 


Hay. 


Potatoes. 


507 


507 


494 


471 


465 


455 


458 


441 


66 


64 


58 


56 


61 


57 


50 


58 


389 


367 


350 


349 


401 


431 


387 


439 


38 


22 


70 


24 


42 


34 


15 


12 


not stated 


40 


28 


100 


31 


23 


90 


50 



30 RELATIVE PROPERTIES OF ORGANIC ELEMENTS. 

"weif^ht of some of the more important kinds of vegetable substance you 
are iu the habit of cultivating : — 



Carbon . 
Hydrogen 
Oxygen 
Nitrogen 
Ash . . 

"lOOO* lOOOf 1000* lOOOf lOOOt 1000* lOOOf lOOOf 
The numbers in the above table represent the constitution of the 
plants and seeds, taken in the state in which they are given to cattle or 
are laid up for preservation, and then dried at 230° Fahrenheit. By 
this drying they lost severally as follows : 

1000 parts of Potatoes . . lost . . . 722 parts of water 
ditto of Wheat . . — ... 166 ditto 
ditto of Hay ... — ... 158 ditto 
ditto of Aftermath Hay — . 136 to 140 ditto 
ditto of Oats ... — ... 151 ditto 
ditto ofCloverSeed . — ... 112 ditto 
ditto of Peas ... — ... 86 ditto 
In crops as they are reaped, therefore, and even as they are given for 
food, much water is present. When artificially dried, the carbon ap- 
proaches to one-half of their weight — the oxygen to more than one- 
lhird§ — the hydrogen to little more than 5 per cent. — and the nitrogen 
rarely to more than 2h per cent. These proportions are variable, but 
they represent very nearly the relative weights in which these elements 
enter into the constitution of those forms of vegetable matter which are 
raised in the greatest quantity for the support of animal life. 

But, besides the organic part, vegetable substances contain an inor- 
ganic portion, which remains behind in the form of ash when tire plant is 
consumed by fire, or of dust when it decomposes and disappears in 
consequence of natural decay. 

In the dried hay, oats, &c., of which the composition is represented 
in the above table, we see that the quantity of ash is very variable, in 
oats being as small as 4 per cent., while of hay every liundred pounds 
left 10 of ash. A similar dilference is observed generally to prevail 
throughout the vegetable kingdom. Each variety of plant, when 
burned, leaves a weight of ash, more or less peculiar to itself. Herba- 
ceous plants generally leave more than the wood of trees — and differ- 
ent parts of the same plant yield unlike quantities of inorganic matter.|| 

• Boussingault Annales de Chim. et de Phys. (183S) lxvii. p. 20 to 38. 

t Ditto ditto (1839) Lxxi. p. 113tol3G. 

i Ditto ditto (1836) lxix. p. 356. 

§ This will appear no way inconsistent with the statement in the former Lecture, that 
oxygen constitutes one half by weight of all living plants, when it is recollected that of the 
water driven off in drying these plants eiglit-ninihs by weight consist of oxygen, and that 
600 lbs. of grass, for example, yield only from 80 to 100 lbs. of hay. 

n Thus of the oak, the dried bark left 60 of ash— the dried leaves 53— the dried alburnuiT 
4— and the dried wood only 2 parts in a thousand of ash.— £>« Saussure. 



ON THE CONSTITUTION OF THE ATMOSPHERE. 31 

These facts are of great imporlance in the theory and in the enlightened 
practice of agricuhure. They will hereafter come under special and 
detailed consideration, when we shall have examined the nature of the 
soils in which ])lants grow, and shall he prepared to consider the chemi- 
cal nature, the source, and the functions, of the inorganic compounds 
which exist in living animal and vegetable substances. 

§ 3. Of the form or state of combination in which the organic elements 
enter into and minister to the growth of plants. 

From the details already presented in the preceding Lecture, in re- 
gard to the properties of carbon and nitrogen, and the circumstances 
under which they are met with in nature, — it will readily occur to you 
that neither of these elementary bodies is likely to enter directly, or in a 
simple state, into the circulation of plants. The former (carbon) being 
a solid substance, and insoluble in water, cannot obtain admission into 
the pores of the roots, the only ])arts of the f)lanls with which, in nature, 
it can come in contact. The latter (hydrogen) does not occur either in 
the atmosphere or in the soil in any appreciable (juantity, and hence, in 
its simple state, forms no part of the food of plants. Oxygen and nitro- 
gen, again, both exist in the atmosphere in the gaseous state, and the 
former is known to be inhaled, under certain conditions, by the leaves 
of plants. Nitrogen may also in like manner be absorbed by the leaves 
of living plants, but, if so, it is in a quantity so small as to have hitherto 
escaped detection. The two latter substances (oxygen and nitrogen) 
are also slightly soluble in water, and, besides being inhaled by the 
leaves, may occasionally be absorbed in minute (|uantiiy along with the 
water taken in by the roots. But by far the largest proportion of these 
two elementary bodies, and the whole of the carbon and hydrogen 
which find their way into the interior of plants, have previously entered 
into a state of mutual combination — forming what are called distinct 
chemical compounds. Before describmg the nature and constitution of 
these compounds, it will be proper to explain, 1°. the constitution of the 
atmosphere in which plants live, and, 2°. the nature of chemical com- 
bination and the laws by which it is regulated. 

§ 4. On the constitution of the atmosphere. 

The air we breathe, and in which plants live, is composed principal- 
ly of a mixture of oxygen and nitrogen gases, in the proportion very 
nearly of 21 of the former to 79 of the latter. It contains, however, as 
a constituent necessary to the very existence of vegetable life, a small 
per centage of carbonic acid. On an average this carbonic acid 
amounts to about 23~^th part* of the bulk of the air. On the shores 
of the sea, or of great lakes, this quantity diminishes; and it becomes 
sensibly less as we recede from the land. Tt is also less by day than 
by night (as 3*38 to 4*32), and over a tnoist than over a dry soil. 

The air is also imbued with moisture. Watery vapour is every 
where diffused through it, but the quantity varies with the season of 
the year, with the climate, with the nature of the locality, with its alti- 

* 0'04 per cent. The mean of 104 experiments made by Saussure at Geneva at all times 
of the year and of the day gave 4 15 volumes in lOOLK). The majtimum was 574, and the 
minimum 3 15. 



32 NATURE OF CHEMICAL COMBINATION. 

tude, and with ifs distance from the equator. In temperate climates, 
it oscillates on the same spot between i and li per cent, of the weight 
of the air ; being least in mid-winter and greatest in the hot months of 
summer. Tliere are also mingled with the atmosphere, traces of the 
vast variety of substances which are capable of rising from the surface 
of the earth in the form of vapour; such, for example, as are given ofT 
by decaying animal or vegetable matter — which are the produce of 
disease iti either class of bodies— or which are evolved during the oper- 
ations of nature in the inorganic kingdom, or by the artificial processes 
of man. Among tliese accidental vapours are to be included those 
miasmata, which, in certain parts of the world, render whole districts 
unhealthy, — as well as certain compounds of ammonia, which are infer- 
red to exist in the atmosphere, because they can be detected in rain 
water, or in snow which has newly fallen. 

In this constitution of the atmosphere we can discover many beauti- 
ful adaptations to the wants and structure of animals and plants. The 
excirinf]; effect of pure oxygen on the animal economy is diluted by the 
large atbnixture with nitrogen ; — the quantity of carbonic acid present 
is sufficient to supply food to the plant, while it is not so great as to 
prove injurious to the animal ; — and the watery vapour suffices to 
maintain the requisite moisture and flexibility of the parts of both or- 
ders of beings, without in general being in such a proportion as to prove 
hurtful to eilther. 

The air also, by its subtlety, diffuses itself ever\'where. Into every 
pore of the soil it makes its way. When there, it yields its oxygen or 
its carbonic acid to the dead vegetable matter or to the living root. A 
shower of rain expels the half-corrupted air, to be succeeded by a purer 
portion as the water retires. The heat of the sun warms the soil, and 
expands the imprisoned gases, — these partially escape, and are, as be- 
fore, replaced by other air when the rays of the sun are withdrawn. 

By the action of these and other causes a constant circulation is, to 
a certain extent, kept up, — between the atmosphere on the surface, 
which plays among the leaves and stems of plants, and the air which 
mingles with the soil and min-isters to the roots. The precise effect and 
the importance of this provision will demand our consideration in a fu- 
ture lecture. 

§5. The nature and laws of chemical combination. 

The terms combine and combination in chemical language have a 
strict and precise application. If sand and saw-dust be rubbed togeth- 
er in a mortar they may be intimately intermingled, but by pouring wa- 
ter on the mass we can separate the particles of wood and leave the 
sand unchanged behind. So if we stir oatmeal and water together, we 
niay cause them perfectly to mix together, but by the aid of a gentle 
heat we can expel the water and obtain dry oatmeal in its original 
condition. Or, by putting salt into water, it will dissolve and disappear, 
and form what is called a solution, but by boiling it down, as is done 
in our salt-pans, the water may be entirely removed and the salt 
procured of the weight originally employe J and possessed of its original 
properties. 

In none of these cases has any chemical action taken place, or any 



I 



CHEMICAL DECOMPOSITIOrf. 33 

permanent change been produced, upon any of the substances. The two 
former were merely mixtures. 

In all cases of chemical action a permanent change takes place in some 
of the substances employed ; and this change is the result either of a chem- 
ical combination^ or of a chemical decomposition. 

Thus when sulphur is burned in the air, it is converted into white va- 
pours possessed of a powerful and very unpleasant odour, and which 
continue to be given oif until the whole of the sulphur is dissipated. 

Here a solid substance is permanently changed into noxious vapours 
which disappear in the air, and this change is caused by ihe combination 
of the sulphur with the oxygen of the atmosphere. 

In like manner when limestone is put into a kiln and strongly heated 
or burned, it is changed or converted into quicklime — a substance very 
♦liferent in its properties from the natural limestone employed. But 
,liis is a case of chemical decomposition. The limestone consists of 
lime and carbonic acid. By the heat these are separated, the latter is 
driven oif and the former remains in the kiln. 

Again, when a jet of hydrogen gas is kindled in the air or in oxygen 
gas, it burns wiih a pale yellow flame. If a cold vessel be held over 
this flame, it speedily becomes bedewed with moisture, anddrojjs of wa- 
ter collect upon it. How remarkable the change which hydrogen un- 
dergoes during this combustion! It unites wiih the oxygen of the 
atmosphere and forms water. How different in its properties is this 
water from either the oxygen or the hydrogen by the union of which it is 
formed! The former a liquid, the latter gases; the former an enemy 
to all combustion, while of the latter, the one (hydrogen) burns readily, 
the other (oxygen) is the very life and support of combustion in all oth- 
er bodies. 

1°. It appears, therefore, that chemical combination or decomposition 
is always attended by a permanent change. 

2°. That when combination takes place, a new substance is formed 
differing in its properties from any of those from which it was produced, 
or of which it consists. 

When two or more elementary bodies thus unite together to form a 
new substance, this new substance is called a chemical compound. 
Thus water is a compound (not a mixture) of the two elementary bodies 
oxygen and hydrogen. 

Now when such combination takes place, it is found to do so always 
in accordance with certain fixed laws. Thus : 

I. Bodies unite together cndy in conetant and definite proportions. We 
can mix togetlier oxygen and hydrogen gases, for example, in any pro- 
portion, a gallon of the one with any number of gallons of the other, but 
if we burn two gallons of hydrogen gas in any greater number of gallons 
of oxygen, they will only consume or unite with one gallon of the oxy- 
gen, the rest of this gas remaining unchanged. A quantity of water will 
be formed by this union, in which the whole of the hydrogen will be 
contained, combined with all the oxygen that has disappeared. Under 
no circumstances can we burn hydrogen so as to cause it to consume 
more oxygen, or from a given weight of hydrogen to produce more than 
a known weight of water. And as oxygen is nearly sixteen times 
heavier than nitrogen, it is obvious that one gallon of the former is about 



34 EQUlVAIiENT NUMBERS — ISOMERIC BODIES. 

eight times heavier than two gallons of the latter, so that by weight these 
two gases, when thus burned, unite together nearly in the proportion 
of 1 to 8, — one pound of hydrogen forming nine pounds of water. 

Again, when pure carbon is burned in the air, it unites with a fixed 
and constant weight of oxygen to form carbonic acid; it never unites 
with more, and it does not tbrm carbonic acid when it unites with less. 

Now this law of fixed and definite proportions is found to hold in re- 
gard to all bodies, and in all cases of chemical combination. Thus we 
have seen that — 
By weight. By weight. 

1 of hydrogen combines with 8 of oxygen to form water. 

So 6 of carbon combine . . . 8 carbonic oxide, 

and 14 of nitrogen 8 .... . nitrous oxide. 

Hence 1 of hydrogen, 6 of carbon, and 14 of nitrogen unite respec- 
tively with the weight (8) of oxygen. These several numbers, there- 
fore, are said to be equivalent to each other (they are equivalent numbers). 
Or they represent the fixed and definite proportions in which these seve- 
ral substances combine together (they are definite proporti on ah). Some 
chemists consider these numbers to represent the relative weights of the 
atoms or smallest particles of which the several substances are made uj), 
and hence not unfrequently speak of them as the atomic weights of these 
substances, or more shortly their atoms. 

For the sake of brevity, it is often useful to represent the simple oi 
elementary bodies shortly by the initial letter of their names. Thus 
hydrogen is represented by H, carbon by C, and nitrogen by N, and 
these letters are used to denote not only the substances themselves, but 
that quantity which is recognised as its equivalent, proportional, or 
atomic weight. Thus : 

Equivalent 
Symbol. or atomic Name, 

weights. 

13 denotes 1 by weight, of iiydrogen. 

C . . . 6 carbon. 

O. . . 8 oxygen. 

N. . . 14* nitrogen. 

Chemical combination is expressed shortly by placing these letters in 
juxta-posiiion,or sometimes in brackets, with the sign plus (-(-) between 
them. Thus HO or (H + O) denotes the combination of one atom or 
equivalent of hydrogen with one of oxygen, that is, water ; and at the 
same time a weight of water (9), equal to the sum of the atomic weights 
(I -f 8) of hydrogen and nitrogen. 

A number prefixed or appended to a symbol, denotes that so many 
equivalents of the substance represented by the symbol are meant, as 
that number expresses. Thus 2 H O, 3 H O, or 3 (B + O), mean two 
or three equivalents of water, 3 H, or H3 three equivalents of hydrogen, 
and 4 C or C4, 2 N or Ngi four of carbon and two of nitrogen respec- 
tively. 

II. Not only are the quantities of the substances which unite together 
definite and constant, but the properties or qualities of the substances 
formed are in general equally so. The properties of pure water or o** 

♦ More correctly 1, 6 13, 8013, and 14 19. 



II 



LAW OF MULTIPLE PROPORTIONS. 35 

carbonic acid are constant and invariable under whatever circumstances 
they may be formed, and the elements of which they consist, when they 
combine together in the same proportions, are never known to form any 
other compounds but water and carbonic acid. 

This law, however, though generally, is not universally true. Many 
substances are known which contain the same elements united together 
in the same proportions, and which, nevertheless, possess very different 
properties. Oil of turpentine and oil of lemons are in this condition. 
They both consist of tiie same elements, carbon and hydrogen, united 
together in the same proportions, and yet their sensible properties as well 
as their chemical relations* are very dissimilar. 

Cane sugar, starch, and gum, all of them abundant products of the 
vegetable kingdom, consist also of the same elements, carbon, hydro- 
gen, and oxygen, united together in the same proportions, and may even 
be represented by the same formula (C,2 Hjo O^o)^! and yet these 
substances are as unlike to each other in their properties, as many 
bodies are of which the chemical composition is very different. To 
compounds thus differing in their properties, and yet containing the 
same elements, in the same proportions, chemists have given the name 
of Isomeric bodies. I shall have occasion to make you more familiar 
with some of them hereafter. 

.3^. Another important law by which chemical combinations are 
regulated, is known by the name of the law of multiple proportions. 
Some substances are observed to be capable of uniting together in more 
than one proportion. Thus carbon unites with oxygen in several pro- 
portions, forming carbonic oxide, carbonic acid, oxalic acid, &c. Now 
when such is the case, it is found that the quantity (the weight) of each 
substance which enters into the several compounds, if not actually re- 
presented by the equivalent number or atomic weight, is represented by 
some simple multiple of that number. Thus two equivalents of carbon 
unite with 2, 3, or 4 equivalents of oxygen, to form carbonic oxide, 
oxalic acid, and carbonic acid respectively, — while one of nitrogen unites 
with 1, 2, 3, 4, or 5 of oxygen to form a series of compounds, of which 
the last (N O5), nitric acid, is the only one I shall have frequent occa- 
sion to speak of in the present lectures. 

This law of multiple proportions, though of great importance in 
chemical theory, 1 do not further illustrate, as we shall have very little 
occasion to refer to it in the discussion of the several topics which will 
hereafter come before us. 



Having thus briefly explained the nature and laws of chemical com- 
bination, I proceed to make you acquainted with those chemical com- 
pounds of the organic elements which are known or are supposed to 
minister to the growth of plants. 

The number of compounds which the four organic elements form 
with each other is almost endless ; but of this number a very few only 

* By the chemical relations of a substance are meant the effects which are prodncei 
upon it by contact with other chemical substances. 

f This/ormuZa means that starch, gum, and sugar, consist of 12 equivalents of carboo 
united to 10 of hydrogen and 10 of oxygen. 



36 RELATIONS Or WATER TO VEGETABLE LIFE. 

are known to minister directly to the growth or nourishment of plants. 
Of these, water, carbonic acid, ammonia, and nitric acid, are the most 
important ; but it will be necessary shortly to advert to a few others, of 
the occurrence or production or action of which we may hereafter have 
occasion to speak. 

§ 6. Of water and its relations to vegetable life. 

Water ig a compound of oxygen and hydrogen in the proportion, 
already stated, of 8 of the former to 1 of the latter by weight, or of 1| 
volume of oxygen to 2 of hydrogen. 

It is more universally difflised throughout nature than any other 
chemical compound with which we are acquainted, performs most im- 
portant functions in reference to animal and vegetable life, and is en- 
dowed with properties by which it is wouderfully adapted to the exist- 
ing condition of things. 

We are familiar with this substance in three several states of cohe- 
sion, — in the solid form as ice, in the fluid as water, and in the gaseous 
as steam. At 32° F. and at lower temperatures, it continues solid, at 
higher temperatures it melts and forms a liquid (water), which a 
212° F. begins to boil and is converted into steam. By this change its 
bulk is increased 1700 times, and it becomes nearly two-fifths lighter 
than common air, [common air being 1, steam is 0-62.] It therefore 
readily rises into and diffuses itself through the atmosphere. 

I. There are only one or two circumstances in which water in the solid 
form materially affects or interferes with the labours of the agriculturist. 

1°. During the frost of a severe winter, the soil contracts and appears 
to shrink in. But the water contained in its pores freezes and expands, 
and the minute crystals of ice thus formed separate the particles of the 
soil from each other. This expansion of the water in dry soils may not 
be equal to the natural contraction of the soil itself, yet still it is suffi- 
cient to cause a considerable separation of the earthy particles through- 
out the whole frozen mass. When a milder temperature returns, and a 
thaw commences, the soil expands and gradually returns to its former 
bulk ; but the outer layers thaw first, and the particles being previously 
separated by the crystals of ice, and now loosened by the thaw, fall off 
or crumble down, and thus the soil becomes exposed to the mellowing 
action of the atmosphere, which is enabled everywhere to pervade it. 
On heavy clay land this effect of the winter's frost not unfrequently 
proves very beneficial.* 

2°. In the form of snow it has been often supposed to be beneficial to 
winter wheat and other crops. That a heavy fall of snow will shelter 
and protect the soil and crop from the destructive effects of any severe 
cold which may follow, there can be no doubt. It forms a light porous 
covering, by which the escape of heat from the soil is almost entirely 
prevented. It defends the young shoots also from those alternations of 
temperature to which the periodical return of the sun's rays continually 

• This alternate contraction and expansion is often injurious to the practical farmer in 
thrmcing out his winter wheat. Some varieties are said to be more thrown out than others, 
and this peculiarity is sometimes ascribed to the longer and stronger roots which shoot from 
one variety than from another ; it may, however, be occasionally owing to the different na- 
ture of the soils in which the trials have been made, or when, in the same soil, to the differ. 
ent states of dryness at different times. 



ACTION AND PROPERTIES OP SNOW. 37 

exposes them ;* and when a thaw arrives, by slowly melting, it allows 
the lender herbage gradually to accustom itself to the milder atmosphere. 

In this manner there is no doubt that a fall of snow may often be of 
great service to the practical farmer. But some believe that winter 
wheat actually thrives under snow. On this point I cannot speak from 
personal knowledge, but 1 will here mention two facts concerning snow, 
which may possibly be connected with its supposed nourishing quahty. 

In the tirst place, snow generally contains a certain quantity of ammo- 
nia, or of animal matter which gives otf ammonia during its decay. 
Tins quantity is variable, and is occasionally so small as to be very dif- 
ficult of detection. Liebig found it in the snow of the neighbourhood of 
Giessen, and I have this winter detected traces of it in the snow which 
fell in Durhamf during two separate storms. This ammonia is present 
in greater quantify in the first portions that fall and lie nearest the plant. 
Hence if the plant can grow beneath the snow, this ammonia may affect 
its growth ; or when the first thaw comes it may descend to the root, and 
may there be imbibed. Rain water also contains ammonia, but when 
rain falls in large quantity it runs off" the land, and may do less good than 
the snow, which lies and melts gradually. [For the properties of am- 
monia, see Lecture III.] 

Another singular property of snow is the power it possesses of ab- 
sorbing oxygen and nitrogen from the atmosphere, in proportions very 
different from those in which they exist in the air. The atmosphere, as 
already stated, contains 21 percent, of oxygen by volume (or bulk), but 
the air which is present in the pores of snow has been found by various 
observers to contain a much smaller quantity. Boussingault [Annalen 
derPhysick (Poggendorf), xxxiv., p. 211,] oljtained from air disengaged 
by melting snov^^ 17 per cent, of oxygen only, and De Saussure found 
still less. The difficulty of respiration experienced on very high moun- 
tains has been attributed to the nature of the air liberated from snow 
when melted by the sun's rays. Whether the air retained among the 
pores of the snow, which in severe winters covers our corn-fields, be 
equally deficient in oxygen with that examined by Boussingault, and 
whether, if it be, the abundance of nitrogen can at all affect vegetation, 
are matters that still remain undetermined. 

II. In the fluid state, that of water, the agency of this compound in 
reference to vegetable life, though occasionally obscure, is yet every- 
where discernible. 

Pure water is a colourless transparent fluid, destitute of either taste or 

* The effects of such alternations are seen on the occurrence of a night's frost in spring. 
If the sun's rays fall in the early morning, on a frozen shoot, it droops, withers, and black- 
ens—it is destroyed by the frost. If the plant be in a shaded spot, where the sun does not 
reach it till after the whole atmosphere has been gradually heated, and the frozen tissue 
slowly thawed, its leaves sustain little injury, and the warmth of the sun's rays, instead of 
injuring, cherish and invigorate it. This effect of sudden alternations of temperature on or- 
ganic matter explains many phenomena, to which it would here be out of place to advert. 

A thick light covering of porous earth not beaten down preserves the potatoe pit from the 
effects of the frost better than a solid compact coating of clay, in the same way as snow 
protects the herbage better than a sheet of ice; an4 it is because of the porosity of the 
covering, that ice may be preserved more effectually, and for a longer period, in a similar 
pit, than in many well-constructed ice-houses. 

t By adding two drops of sulphuric acid to four pints of snow water, evaporating to dry. 
nesa, and mixing the dry mass with quicklime or caustic potash. The residual mass con- 
tained a brown organic matter, mixed with the sulphate of ammonia. 

4 



38 WATER NECESSARY TO LIFE — ITS SOLVENT POWER. 

smell. It enters largely into the constitution of all living animals and 
plants, and forms upwards of one half of the weight of all the newly 
gathered vegetable substances we are in the habit of cultivating or col- 
lecting for the use of man. [See page 30.] 

Not only does it enter thus largely into the constitution of all ani- 
mals and plants, but in the existing economy of nature its presence in 
large quantities is absolutely necessary to the. persistence of animal and 
vegetable life. In the midst of abundant springs and showers, plants 
shoot forth with an amazing rapidity, while they wither, droop, and die, 
when water is withheld. How much the manifestation of life is de- 
pendent upon its presence, is beautifully illustrated by some of the hum- 
bler tribes of plants. Certain mosses can be kept long in the herbarium, 
and yet will revive again when the dried specimens are immersed iu 
water. At Manilla a species of Lycopodium grows upon the rocks, 
which, though kept for years in a dried state, revives and expands its 
foliage when placed in water [the Spaniards call it Triste de Corazon, 
Sorrow of the Heart. — BurneVs \Vanderings,\). I'i.'] Thus life lingers 
as it were, unwilling to depart and rejoicing to display itself again, when 
the moisture returns.* 

There are, however, three special properties of water, which are in 
a high degree interesting and important to the practical agriculturist, 
and to which I beg to direct your particular attention. These are : 

1°. Its solvent power; 

2^. Its affinity for certain solid substances ; and, 

3°. The degree of affinity by which its own elements are held to- 
gether. 

1°. When pure boiled water is exposed to the air, it gradually ab- 
sorbs a quantity of the several gases of which the atmosphere is com- 
posed, and acquires more or less of a sparkling appearance and an agree- 
able taste. The air which it thus absorbs amounts to about ^\h of its 
own bulk, and is entirely expelled by boiling. When thus expelleil, 
this air, like that obtained from snow, is found on examination to contain 
the oxygen, nitrogen, and carbonic acid in proportions very different from 
those in which they exist in the atmosphere. In the latter, oxygen i^ 
present to the amount of only 21 per cent, by volume, while the air ab- 
sorbed by water contains 30 to 32 per cent, of the same gas. In like 
manner, the mean quantity of carbonic acid in the air does not exceed 
TTToim'^^ parts (0-05 per cent.) of its bulk, while that expelled from water, 
which has been long exposed to the air, varies from 11 to 60 ten ihou- 
sj{nd parts (O-ll to 0-6f per cent.) 

* In some species of animals, life is in like manner stispenrlerl by the absence of water. 
Tlie inhabitants of some land and even marine shells may be dried and preserved for a long 
time in a state of torpor, and afterwards revived by immersion in water. The Cerilhium 
Armatum has been brought from the Mauritius in a dry state, while snails are said to have 
been revived after beina dried for 15 years. The vibrio tritici (a species of worm), was re- 
fjtored by Mr. Bauer, after an apparent death of nearly six years, by merely soakina it irj 
water. The Furcularia Anastobea, a small microscopic atjimal, may be made to undergo 
apparent death and resuscitation many times, by alternate drying and moistening. Accord- 
ing to Spallanzani, animalculi have been recovered by moisture, after a torpor of 27 years. 
These facts tend to lessen our surprise at the alleged longevity of the seeds of plants. 

t Of these gases when unmixed, water ab.sorbs very different quantities. Thus 100 vo- 
himes of water at 60° F.. ab.sorbS 55 of oxygen, 153 of hydrogen, 1 47 of nitrogen, {Henry,) 
JOG of carbonic acid, or 7800 of ammonia. 



ITS AFFINITY FOR SOLID SUBSTANCES. 39 

Thus when water falls in rain or trickles along the surface of the 
land, it absorbs these gaseous substances, carries them with it wherever 
it goes, conveys them to the roots, and into the circulation of plants, and 
thus, as we shall hereafter see, makes them all minister to the growth 
and nourishment of living vegetables. 

Again, water possesses the power of dissolving many solid substances. 
If sugar or salt be mixed with water in certain quantities, they 
speedily disappear. In like manner, many other bodies, both simple 
and compound, are taken up by this liquid in greater or less quan- 
tity, and can only be recovered by driving off the water, through the aid 
of heat. 

Thus it happens that the water of our springs and rivers is never 
pure, but holds in solution more or less of certain solid substances. 
Even rain water, washing and purifying the atmosphere as it descends, 
brings down portions of solid matter which had previously risen into the 
air in the form of vapour, and as it afterwards flows along or sinks into 
the surface of the soil, it meets with and dissolves other solid substances, 
the greater portion of which it carries with it wherever it enters. In 
this way solid substances are conveyed to the roots of plants in a fluid 
form, which enables them to ascend with the sap ; and the supply of 
these naturally solid substances is constantly renewed, by the succes- 
sive passage of new portions of flowing water. We shall hereafter be 
able to see more clearly and to ai)preciate more justly this beautiful ar- 
rangement of nature, as well as to understand how indispensable it is to 
the continued fertility of the soil. 

Nor is it merely earthy and saline substances which the water dis- 
solves, as it thus percolates through the soil. It takes up also sub- 
stances of organic origin, especially portions of decayed animal and ve- 
getable matter,- — such as are supposed to be capable of ministering to 
the growth of plants, — and brings them within reach of the roots. 

This solvent power of water over solid substances is increased by an 
elevation of temperature. Warm water, for example, will dissolve 
Epsom salts or oxalic acid in much larger quantity than cold water 
will, and the same is true of nearly all solid substances which this fluid 
is capable of holding in solution. To this increased solvent power of 
the water they absorb, is ascribed, among other causes, the peculiar 
character of the vegetable productions, as well as their extraordinary 
luxuriance, in many tropical countries. 

2°. But the affinity which water exhibits for many solid substances is 
little less important and remarkable. 

When newly burned lime is thrown into a limited quantity of water 
the latter is absorbed, while the lime heats, cracks, swells, and finally 
falls to a white powder. When thus perfectly slaked, it is found 4o be 
one-third heavier than before — every three tons having absorbed one 
ton of water. This water is retained in a solid form, more solid than 
water is when in the state of ice, and it cannot be entirely separated 
from the lime without the application of a red heat. When you lay 
upon your land, therefore, four tons of slaked lime, you tnix with your 
soil one ton of water, which the lime afterwards gradually gives up, 
either in whole or in part, as it combines with other substances. To 
this fact wo shall return when we hereafter consider the various wavs 



40 USES or WATERY VAPOUR IN VEGETATION. 

in which lime acts, when it is employed by the farmer for the purpose 
of improving his land. [See the subsequent lecture, " On the action of 
lime when employed as a manure.^'] 

For clay also, water has a considerable affinity, though by no means 
equal to that which it displays tor quicklime. Hence, even in well- 
drained clay lands, the hottest summer does not entirely rob the clay of 
its water. It cracks, contracts, and becomes hard, yet still retains 
water enough to keep its wheat crops green and flourishing, when the 
herbage on lighter soils is drooping or burned up. 

A similar affinity for water is one source of the advantages which are 
known to follow from the admixture of a certain amount of vegetable 
matter with the soil; though, as in the case of charcoal, its porosity* 
is probably more influential in retaining moisture near the roots of 
the plants. f 

3°. The degree of affinity by which the elements of water are held 
together, exercises a material influence on the growth and production 
of all vegetable substances. 

If I burn a jet of hydrogen gas in the air, ivater is formed by the 
union of the hydrogen with the oxygen of the atmosphere, for which it 
manifests on many occasions an apparently powerful affinity. But if 
into a vessel of water I put a piece of iron or zinc and then add sulphuric 
acid, the water is decomposed and the hydrogen set free, while the 
metal combines with the oxygen. 

So in the interior of plants and animals, water undergoes continual 
Jecom position, and recomposition. In its fluid state, it finds its way 
and exists in every vessel and in every tissue. And so slight, it would 
appear, in such situations, is the hold which its elements have upon 
each other— or so strong their tendency to combine with other substan- 
ces, that they are ready to separate from each other at every impulse — 
yielding now oxygen to one, and now hydrogen to another, as the pro- 
duction ofthe several compounds which each organ is destined to elab- 
orate respectively demands. Yet with the same readiness do they 
again re-attach themselves and cling together, when new metamorphoses 
require it. It is in the form of water, indeed, that nature introduces 
the greater portion of the oxygen and hydrogen which perform so im- 
portant a part in the numerous and diversified changes which take place 
in the interior of plants and animals. Few things are really more won- 
derful in chemical physiology, than the vast variety of transmutations 
which are continually going on, through the agency of the elements of 
water. 

III. In the state of vapour water ministers most materially to the 
life and growth of plants. It not only rises into the air at 212° Fahr. 
whervit begins to boil, but it disappears or evaporates from open vessels 
at almost every temperature, with a rapidity proportioned to the previ- 
ous dryness ofthe air, and to the velocity and temperature of the at- 
mospheric currents which pass over it. Even ice and snow are grad- 

• Affinity for water causes vegetable matter to combine chemically with it, porosHy cause* 
it merely to drink in the water mechanically, and to retain it, unchanged, in its pores. 

t For an exposition of the intimate relation of water to the chemical constitution of the 
solid parts of livin^r vegetables, see a subsequent Lecture, " On the nature and production 
of the substances of which plants chiefly consist. " 



FORMATIOJy OF CLOUDS AMD RAIN. 41 

ually dissipated in the coldest weather, and sometimes with a degree 
of velocity which at first sight seems truly surprising.* 

It thus happens that the atmosphere is constantly impregnated with 
watery vapour, which in this gaseous state accompanies the air where- 
ever it penetrates, permeates the soil, pervades the leaves and pores of 
plants, and gains admission to the lungs and general vascular system of 
animals. We cannot appreciate the influence which, in this highly 
comminuted form, water exercises over the general economy of organic 
nature. 

But it is chiefly when it assumes the form of rain and dew, and re- 
descends to the earth, that the benefits arising from a previous conversion 
of the water into vapour become distinctly appreciable. The quantity 
of vapour which the air is capable of holding in suspension is depend- 
ent upon its temperature. At high temperatures, in warm climates, or 
in warm weather, it can sustain more — at low temperatures less. 
Hence when a current of comparatively warm air loaded with moisture 
ascends to or comes in contact with a cold mountain top, it is cooled 
down, is rendered incapable of holding the whole of the vapour in sus- 
pension, and therefore leaves behind in the form of a mist or cloud, a 
portion of its watery burden. In rills subsequently, or springs, the 
aqueous particles which float in the midst, re-appear on the plains be- 
neath, bringing nourishmenif at once, and agreateful relief to the thirsty 
soil. 

So when two currents of air charged with moisture, but of unequal 
temperature, meet in the atmosphere, they mix, and the mixture has 
the mean temperature of the two currents. But air of this mean tem- 
perature is incapable of holding in suspension the mean quantity of wa- 
tery vapour ; hence, as before, a cloud is formed, and the excess of 
moisture falls to the earth in the form of rain. In descending to refresh 
the earth, this rain discharges in its progress another office. It washes 
the air as it passes through it, dissolving and carrying those accidental 
vapours which, though unwholesome to man, are yet fitted to minister 
to the growth of plants. 

The dew, celebrated through all times and in every tongue for its sweet 
influence, j)resents the most beautiful and striking illustration of the agen- 
cy of water in the economy of nature, and exhibits one of those wise and 
bountiful adaptations, by which the whole system of things, animate and 
inanimate, is fitted and bound together. 

All bodies on the surface of the earth radiate, or throw out rays 
of heat, in straight lines — every warmer body to every colder ; and the 
entire surface is itself continually sending rays upwards through the 
clear air into free space. Thus on the earth's surface all bodies strive, 
as it were, after an equal temperature (an equilibrium of heat), while 

* Mr. Howard states that a circular patch of snow 5 inches in diameter lost in the month 
of January 150 grains of vapour between sunset and sunrise, and 56 grains more before the 
close of the day, when exposed to a smart breeze on a house-top. From an acre of snow 
this would be equal to 1000 gallons of water during the night only. — ProuV a Bridgewaler 
Treat>.te,p. 302; Encyclopcbd. Metropol,, art. Meteorology. 

In Von Wrangell's account of his visit to Siberia and the Polar sea, translated by Major 
Sabine (p. 390), it is stated that, in the intense cold, not only living bodies— but the very 
S710W — smokes and fills the air with vapour. 

\ For the nature of this nourishment see the subsequent Lectures, " On the inorganic con- 
stituents of plants." 



42 DESCENT OF DEW.-^UNIVERSAL BOUNTY OF NATURE. 

the surface as a whole tends gradually towards a cooler state. But 
while the sun shines this cooling will not take place, for the earth then 
receives in general more heat than it gives offi and if the clear sky be 
shut out by a canopy of clouds, these will arrest and again throw back 
a portion of the heat, and prevent it from being so speedily dissipated. 
At night, then, when ihe sun is absent, the earth will cool the most ; on 
clear nights also more than when it is cloudy, and when clouds only 
partially obscure the sky, those parts will become coolest which look to- 
wards the clearest portions of the heavens. 

Now when the surface cools, the air in contact with it must cool also ; 
and like the warm currents on the mountain side, must forsake a portion 
of the watery vapour it has hitheito retained. . This water, like the float- 
ing mist on the hills, descends in particles almost infinitely minute. 
These particles collect on every leaflet, and suspend themselves from 
every blade of grass, in drops of " pearly dew." 

And mark here a beautiful adaptation. Different substances are en- 
dowed with the property of radiating their heat, and of thus becoming 
cool with different degrees of rapidity, and those substances which in 
the air become cool first, also attract first and most abundantly the par- 
ticles of falling dew. Thus in the cool of a summer's evening the grass 
plot is wet, while the gravel walk is dry ; and the thirsty pasture and ev- 
ery green leaf are drinking in the descending moisture, while the naked 
land and the barren highway are still unconscious of its fall. 

How beautiful is the contrivance by which water is thus evaporated or 
distilled as it were into the atmosphere — largely perhaps from some par- 
ticular spots, — then diffused equably through the wide and restless air,^ 
and afterwards precipitated again in refreshing showers or in long-mys- 
terious dews!* But how much more beautiful the contrivance, I might 
almost say the instinctive tendency, by which the dew selects the objects 
on which it delights to fall ; descending first on every living plant, copi- 
ously ministering to the wants of each, and expending its superfluity 
only on the unproductive waste. 

And equally kind and bountiful, yet provident, is nature in all her 
operations, and through all her works. Neither skill nor materials are 
ever wasted ; and yet she ungrudgingly dispenses her favours, apparent- 
ly without measure, — and has subjected dead matter to laws which 
compel it to minister, and yet with a most ready willingness, to the 
wants and comforts of every living thing. 

And how unceasingly does she press this her example not only of un- 
bounded goodness, but of universal charity — above all other men — on 
the attention of the tiller of the soil. Does the corn spring more 
freshly when scattered by a Protestant hand — are the harvests more 
abundant on a Catholic soil, — and does not the sun shine alike, and the 
dew descend, on the domains of each political party ? 

The beauty of this arrangement appears more striking when we consider that the whole 
of the watery vapour in the air, if it fell at once in the form of rain, would not amount to 
more than 5 inches in depth on the whole surface of the globe. In England the fall of rain 
varies from 22 inches (London, York, and Edinburgh) to 68 (Keswick), while in some few parts 
of the world (St. Domingo) it amounts to as much as 150 inches. The mean fall of rain 
over the whole earth i^s estimated at 32 or 33 inches ; but if we suppose it to be only 10 or 15 
inches, the water which thus fiills will require to be two or three times re-distilled in the course 
of every year. This is exclusive of dew, which in many countries amounts to a very 
large quantity.— See ProuVs Bridgewuter Treatise, p. 309. 



COLD PKODUCED BY EVAPORATION, A> D ITS I>TLUENCE. 43 

So science, from her daily converse with nature, fails not sooner or 
later to take her hue and colour from the perception of this universal 
love and hounty. Party and sectarian differences dvi^indleaway and 
disappear from the eyes of him who is daily occupied in the conlempla- 
lionofthe boundless munificence of the great Impartial ; he sees him- 
self standing in one common relation to all his fellow-men, and feels 
himself to be most completely performing his part in life, when he is 
able in any way or in any measure to contribute to the general welfare 
of all. 

It is in this sense too that science, humbly tracing the footsteps of the 
Deity in all his works, and from them deducing his intelligence and his 
universal goodness — it is in this sense, that science is of no sect, and of 
no party, but is equally the province, and the properly, and the friend of all, 

§ 7. Of the cold produced by the evaporation of water, and its 
injiuence on vegetation. 

Beautiful, however, and beneficent as are the provisions by which, in 
nature, watery vapour is made to serve so many useful purposes, there 
are circumstances in which, and often through the neglect of man, the 
presence of water becomes injurious to vegetation. 

The ascent of water, in the form of vapour, permits the soil to dry, 
and fits it for the labours of the husbandman ; while its descent in dew 
refreshes the plant, exhausted by the heat and excitement of a long 
summe"*^ day. But the same tendency to ascend in vapour, gives rise 
to the c«>id unproductive character of lands in which water is present in 
great excess. This character you are familiar with in what are called 
cold clay soils. 

The epithet cold, applied to such soils, though derived probably from 
no theoretical views, yet expresses very truly their actual condition. 
The surface of the fields in localities where such lands exist, is in reality 
less warm, throughout the year, than tljat of fields of a different quality, 
even in their immediate neighbourhood. This is readily proved, by 
placing the bulb of a thermometer immediately beneath the soil in two 
such fields, when in the hottest day a marked difference of temperature 
will, in general, be perceptible. The difference is dependent upon the 
following principle : — 

When an open pan of water is placed upon the fire, it continues to 
acquire heat till it reaches the temperature of 212° F. It then begins to 
boil, but ceases to become hotter. Steam, however, passes off, and ihe 
water diminishes in quantity. But while the vessel remains upon the 
fire the water continues to receive heat from the burning fuel as it did 
before it began lo boil. But since, as already stated, it becomes no hot- 
ter, the heat received from the fire must be carried off" by the steam. 

Now this is universally true. Whenever water is converted into 
steam, the ascending vapour carries off mixch heat along wilhit. 

This heat is not missed, or its loss perceived, when the vapour or 
steam is formed over a fire ; but let water evaporate in the open air 
from a stone, a leaf, or a field, and it must take heat with it from these 
objects — and the surface of the stone, the leaf, or the field, must become 
colder. That stone or leaf also must become coldest from which the 
largest quantity of vapour rises. 



44 WET AND COLD SOILS IMPROVED BY DRAINING. 

Now, let two adjoining fields be wet or moist in different degrees, that 
which is wettest will almost at all limes give off the largest quantity of 
vapour, and will therefore be the coldest. Let spring arrive, and the 
genial sun will gently warm the earth on the surface of theone, while 
the water in the other will swallow up the heating rays, and cause them 
te re-ascend in the watery vapour. Let summer come, and while the 
Boil of the one field rises at raid-day to perhaps 100° F. or upwards, that 
of the other may, in ordinary seasons, rarely reach 80° or 90° — in wet 
seasons may not even attain to this temperature, and only in long 
droughts will derive the full benefit of the solar rays. I shall hereafter 
more particularly advert to the important influence which a high tempe- 
rature in the soil exercises over the growth of plants, the functions of 
their several parts, and their power of ripening seeds — as well as to 
certain beautiful adaptations by which nature, when left to herself, is 
continually imparting to the soil, especially in northern latitudes, those 
qualities which fit it for deriving the greatest possible benefit from the 
presence of the sun's rays. In the mean time you are willing to con- 
cede that warmth in the soil is favourable to the success of your agricul- 
tural pursuits. What, then, is the cause of the coldness and poverty, 
the fickleness and uncertainty of produce, in land of the kind now al- 
luded to ? It is the presence of too much water. What is the remedy ? 
A removal of the excess of water. And ho^v ? By effectual drainage. 

There are other benefits to the land, which follow from this removal 
of the excess of water by draining, of which it would here be out of 
place to treat; but a knowledge of the above principle shows you that 
the first effect upon the soil is the same as if you were to place it in a 
warmer cHmate, and under a milder sky — where it could bring to ma- 
turity other fruits, and yield more certain crops. 

The application of this merely rudimentary knowledge will enable 
you to remove from many improvable spots the stigma oil being poor and 
cold; an appellation hitherto applied to them, — not because they are by 
nature unproductive, but because ignorance, or indolence, or indifference, 
has hitherto prevented their natural capabilities from being either ap- 
preciated or made available. 



Note.— In reference to the supposed fertilizing effect of snow, adverted to in the above 
lecture, I may mention a fact observed by Heyer, and quoted by Liebig, (p. 125), that willow 
branches immersed in snow water put forth roots three or four times longer than when put 
into pure distilled water, and that the latter remained clear while the snow water became 
coloured. This shows that snow contains something not present in distilled water, which 
Is capable of accelerating the growth of plants. The experiment would have been more 
iniitructive in regard to natural operalions, had the effect of the snow water been coca- 
pared with that of an equal bulk of rain water, collected under similar circumstances. 



LECTURE III. 

Carbonic and oxalic acids, their properties and relations to vegetable life~Carbonic oxide 
and light carburetted hydrogen, their properties and production iu nature'— Ainaionia, its 
properties and relations to vegetable life. 

§ 1. Carbonic acid, its proj^er ties and relations to vegetable life. 

When charcoal is burned in the air it combines slowly with oxygen, 
and is transformed inlo carbonic acid gas. In oxygen gas it burns more 
rapidly and vividly, producing the same compound. 

This gas is colourless, like oxygen, hydrogen, and nitrogen, but is 
readily distinguished from all these, by its acid taste and smell, by its solu- 
bility in water, by its great density, and by its reddening vegetable blues. 
Water at 60 F. and under the ordinary pressure of the atmosphere, dis- 
solves rather more than its own bulk of this gas (100 dissolve 106), and, 
however the pressure may be increased, it still dissolves the same bulk. 

All gases diminish in bulk uniformly as the pressure to which they 
are subjected is increased. Thus under a pressure of two atmospheres 
they are reduced to one-half their bulk, of three atmospheres to one- 
third, and so on. When water, therefore, is saturated wifh carbonic 
acid under great pressure, as in the manufacture of soda water, though 
it still dissolves only its own bulk, yet it retains a weight of the gas 
which is proportioned to the pressure applied. For the same reason 
also, when the pressure is removed, as in drawing the cork from a bot- 
tle of water so impregnated, the gas expands and escapes, causing a 
lively effervescence, and the water retains only its own bulk at the ex- 
isling pressure. This solution in water has a slightly sour taste, and 
reddens vegetable blues. These properties it owes to the presence of 
the gas, which is therefore what chemists call an acid body, and hence its 
name of carbonic acid. [A.cids have generally a sour taste, redden 
vegetable blues, or combine with bases, such as lime, soda, potash, &c., 
to form salts.] 

This gas is one-half heavier than atmospheric air, its density being 
1*524, and hence it may be poured through the air from one vessel to 
another. Hence also, when it is evolved from crevices in the earth, in 
caves, in wells, or in the soil, this gas diffuses itself through the atmos- 
phere and ascends into the air, much more slowly than the elementary 
gases described in the previous lecture. Where it issues from the earili 
in large quantity, as in many volcanic districts, it flows along the surface 
like water, enters into and lills up cracks and hollows, and sometimes 
reaches to a considerable distance from its source, before it is lost among 
the still air. 

Burning bodies are extinguished in carbonic acid, and living beings, 
plunged into it, instantly cease to breathe. Mixed with one-ninth of its 
bulk of this gas the atmospheric air is rendered unfit for respiration. It 
is, however, the principal food of plants, being absorbed by their leaves 
and roots in large quantity. Hence the presence of carbonic acid in the 
atmosphere is necessary to the growth of plants, and they have beenob- 



46 CARB051C ACID. — EVIDENCE OF UKITY OF DESIGN. 

served to thrive better when tlie quantity of this gas in the air is con- 
siderably augmented. Cominon air, as has been already stated, does 
not contain more on an average thang^^no^h of its bulk of carbonic acid, 
but De Saussure found that plants in the sunshine grew better when it 
was increased to y^h of tlie bulk of t}}e air, but beyond this quantity 
they were injured by its presence, even when exjiosed to the sun. 
When the carbonic acid amounted to one-half, the plants died in seven 
days ; when it reached two-thirds of the bulk of the air, they ceased to 
grow altogether. In the shade any increase of carbonic acid beyond 
that which naturally exists in the atmosphere of* our globe, was Ibund 
to be injurious. 

These circumstances it is of importance to remember. Did the sun 
always shine on every part of the earth's surface, the quantity of carbo- 
nic acid in the atmosphere might probably have been increased with ad- 
vantage to vegetation. But every such increase would have rendered 
the air less lit for the respiration of existing races of animals. Thus 
we see that not only the nature of living beings, both ])lanis and ani- 
mals, but also the periodical absence of the sun's ra3's, have been taken 
into account in the present arrangement of things. 

In perpetual sunshine plants would flourish more luxuriantly in air 
containing more carbonic acid, but they would droop and die in the 
shade. This is one of those \)roofs o[ wnity of design which occasion- 
ally force themselves upon our attention in every department of nature, 
and compel us to recognise the regulating superintendence of one mind. 
The same hand which mingled the ingredients of the atmosphere, also 
set the sun to rule the day only, — tempering the amount of carbonic 
acid to the time of his periodical j)resence, as well as to the nature of 
animal and vegetable life. 

Carbonic acid consists of one equivalent of carbon and two of oxygen, 
and is represented by CO^. It unites with bases (potash, soda, lime, 
&c.), and forms compounds known by the name of carbonate. Thus 
jjearlash is an impure carbonates of potash, — the common soda of the 
shops, corbonate of soda, — and limestone or clialk, carbonates of lime. 
From these compounds it may be readily disengaged by pouring upon 
them diluted muriatic or sulphuric acids. From limestone it is also 
readily expelled by heat, as in the common lime-kilns. During this 
process the limestone loses nearly 44 per cent, of its weight, [43-7 when 
pure and dry,] a loss which represents the quantity of carbonic acid dri- 
ven off". [Hence by burning limestone on the spot where it is quarried, 
nearly one-half of the cost of transport is saved,] 

Common carbonate of lime, in its various forms of chalk, hard lime- 
stone, or marble, is nearly insoluble in water, but it dissolves readily in 
water containing carbonic acid. Thus, if a current of this gas be pass- 
ed through lime-water, the liquid speedily becomes milky from the 
formation and precipitation of carbonate of lime, but after a sliorl time 
the cloudiness disappears, and the whole of the lime is re-dissolved. 
The application of heat to this clear solution expels the excess of car- 
bonic acid, and causes the carbonate of lime again to fall. 

By exposure to the air, we have already seen that water always ab- 
sorbs a quantity of carbonic acid from the atmosphere. As it after- 
wards trickles through the rocks or through soil containing lime, it grad- 



CARBOMC ACID RENDERS LIME SOLUBLE. 47 

ually dissolves a portion of this earth, equivalent to the quantity of gas 
it holds in solution, and thus reaches the surface impregnated with cal- 
careous matter. Or it carries it in its progress below the surface to the 
roots of plants, where its earthy contents are made available, either di- 
rectly or indirectly, to the promotion of vegetable growth. ' To the lime 
thus held in solution, spring and other waters generally owe their hard- 
ness, and it is the expulsion of the carbonic acid, by heat, that causes 
the deposition of the sediment so often observed when such waters are 
boiled. 

1 propose hereafter to devote an entire lecture to the consideration of 
the action of lime upon land, as it is employed for agricultural pur- 
poses, but I may here remark, that tiiis solvent action of the carbonic 
acid in rain water is one of the principal agents in removing the lime 
from your soils, and in rendering a fresh application necessary after a 
certain lapse of time. It is the cause also of that deposit of calcareous 
matter at the mouths of drains which you not uufrequenlly see in lo- 
calities where lime is laid abundantly upon the land. The greater the 
quantity of rain, therefore, which falls in a district, the less permanent 
will be the etFects of liming the land — the sooner will it be robbed of 
this important element of a fertile soil. Still carbonic acid is only one 
of several agents which act almost unceasingly in thus removing the 
lime from the land, a fact I shall hereafter have occasion more fully to 
explain. 

In nature, carbonic acid is.produced under a great variety of circum- 
stances. It is given off from the limgs of all animals during respira- 
tion. It is formed during the progress of fermentation. Fermented li- 
quors owe their sparkling qualities to the presence of this gas. Dur- 
ing the decay of animal and vegetable substances in the air, in com- 
post heaps, or in the soil, it is evolved in great abundance. In certain 
volcanic countries it issues in large quantity from springs and from 
cracks and fissures in the surface of the earth; while the vast amount 
of carbon contained in the wood and coal daily consumed by burning, 
is carried up into the atmosphere, chiefly in the form of carbonic acid. 
We shall hereafter consider the relation which exists between these 
several sources of supply and the proportion of carbonic acid per- 
manently present in the air and so necessary to the support of vegetable 
life. 

§ 2. Oxalic acidf its properties and relations to vegetable life. 

Oxalic acid is another compound of carbon and oxygen, which, though 
not known to minister either to their growth or nourishment, is yet found 
largely in the interior of many varieties of plants. In an uncombined 
state it exists in the hairs of the chick pea. In combination with potash 
it is found in the wood sorrel (oxalis acetosella), in the common sorrel, 
and other varieties of rwrnear, — in which it is the cause of the acidity of 
the leaves and stems, — in the roots of these plants also, in the leaves and 
roots of rhubarb, and in the roots of torraentilla, bistort, gentian, saponaria, 
and many others. It is this combination with potash, formerly extracted 
from wood sorrel, which is known in commerce by the name oi^ salt of 
sorrel. In combination with lime it forms the principal solid parts of 



48 PROPERTIES OF OXALIC A6ID. 

many lichens, especially of theparfueli^e and variolaria,* some of which 
contain as much oxalate of lime as is equivalent to 15 or 20 parts of pure 
acid in 100 of the dried plant. 

The crystallized oxalic acid of the shops forms transparent colourless 
crystals, of an intensely sour taste. These crystals dissolve readily in 
twice their weight of cold water, and the solution, when sufficiently di- 
lute, is agreeably acid to the taste. This acid is exceedingly poisonous- 
Half an ounce of the crystals is sufficient to destroy life in a very short 
lime, and a quarter of an ounce after the lapse of a few days. It con- 
sists solely of carbon and oxygen in 'the proportion of two equivalents 
of the former to three of the latter. Its symbol is C2O3. It combines 
with bases, and forms salts which are known by the name of oxalates, 
and it is characterised by the readiness with which it combines with lime 
to form oxalate of lime. If a solution of the acid be poured into lime wa- 
ter, the mixture immediately becomes milky from the formation of this 
compound, which is insoluble in water.f It is this oxalate of lirne which 
exists in the lichens, while oxalate of potash exists in the sorrels. 

Oxalic acid is one of those compounds of organic origin which we can- 
not form, as we can form carbonic acid by the direct union of its elements. 
In all our i)rocesses for preparing it artificially, we are obliged to have re- 
course to a substance previously organized in the living plant. It may 
be prepared from sugar, starch, or even from wood, by various chemical 
processes. The usual method is to digest potato starch with five times its 
weight of strong nitric acid (aquafortis), diluted with ten of water, till red 
fumes cease to be given off, and then to evaporate the solution. The ox- 
alic acid separates in crystals, or, as it is usually expressed, crystallizes in 
the solution thus concentrated by evaporation. 

It is not known to exist in the soil or in the waters which reach the 
roots of plants. Where it is found in living vegetables, therefore, it must, 
like the other substances they contain, have been formed or elaborated 
in the interior of the plant itself. By what very simple changes the 
production of this acid is or may be effected, we shall see in a subse- 
quent lecture. 

§ 3. Carbonic oxide, its constitution and properties. 

When carbonic acid (CO2) is made to pass through a tube containing 

red-hot charcoal, it undergoes a remarkable change. Its gaseous form 

remains unaltered, but it combines with a second equivalent of carbon 

(becoming C2O2), which it carries off in the aeriform state. The new 

* The parmeUa cruciataand variolaria communis are mentioned as peculiarly rich in this 
acid, which used to be extracted from them for sale. A species of parmelia, collected after 
the droughts on the sands of Persia and Georgia, contains 66 per cent, of oxniate of lime, 
with about 23 per cent, of a gelatinous substance similar to that obtained from Iceland moss. 
This lichen is used for food by the Kirgliuis. A similar lichen is collected about Bagdad for 
a similar purpose. 

t Substances that are insoluble are generally without action on the animal economv, and 
may be introduced into the stomach without producing any injurious effect. Hence this o.v- 
alate of lime, tliough it contains oxalic acid, is not poisonous. Hence also, if oxalic acid be 
present in the stomach, its poisonous action may be taken away by causing lime water or 
milli of lime to be swallowed in sufficient quantity. The acid combines with the lime, as in 
the experiment described in the text, and forms insoluble oxalate of lime. The common 
magnesia of the shops will serve the same purpose, forming an insoluble oxalate of magnesia. 
It is by performing experiments under circumstances where the results are visible— as in 
glass vessels— that we are enabled to predict the results in circumstances where the phe- 
nomena are not visible, and to act with as much confidence as if we could really see them. 



liiaWT CABBURETTED HTDROGEN. 49 

gas thus produceo is known by the name of carbonic oxide. Ii consists 
of one equivalent of carbon united to one of oxygen, and is represented 
by C2 Og* or simply CO. 

This gas is colourless, without taste or smell, lighter than common air, 
nearly insoluble in water, extinguishes flame, does not support life; 
burns in the air or in oxygen gas with a blue flame, and during this 
combustion is converted into carbonic acid. It is produced along with 
carbonic acid during the imperfect combustion of coals in our fires and 
furnaces, but is not known to occur in nature, or to minister directly to 
the growth of plants. 



There exists a general relation among the three compounds of carbon 
and oxygen above described, to which it may be interesting to advert, 
in connection with the subject of vegetable physiology. This relation 
appears when we compare together their chemical constitution, as re- 
presented by their chemical formula : — 

Carbonic acid consists of one of carbon and two of oxygen, or CO2 ; 

Carbonic oxide, of one of carbon and one of oxygen, or CO ; 

So that if carbonic acid be present in a plant, and be there deprived 
of one equivalent of its oxygen, by any vital action, it will be converted 
into carbonic oxide. 

Oxalic acid consists of two of carbon and three of oxygen, or C2O3. 

If we add together the formulae for 

Carbonic acid = COg and 
Carbonic oxide = CO, we have 

Oxalic acid =z C2O3. 

Hence this acid may be formed in the interior of plants, either by the 
direct union of carbonic oxide and carbonic acid, or by depriving two of 
carbonic acid (2CO2 or C2O4) of one equivalent of oxygen. 

When in a subsequent lecture we have studied the structure and func- 
tions of the leaves of plants, we shall see how very easy it is to under- 
stand the process by which oxalic acid is formed and deposited in the in- 
terior of plants, and by which carbonic oxide also may be, and probably 
is, produced. 

§ 4. Light carburetted hydrogen — the gas of marshes and of coal mines. 

During the decay of vegetable matter in moist places, or under water, 
a light inflammable gas is not unfrequently given offi which differs in its 
properties from any of those hitherto described. In summer it may often 
be seen rising up in bubbles from the bottom of stagnant pools and 
from marshy places, and may readily be collected. 

This gas is colourless, without taste or smell, and is little more than 
half the weight of common air, [its specific gravity, by experiment, is 
0-5576.] A lighted taper, plunged into it, is immediately extinguished, 
while the gas takes fire and burns with a pale yellow flame, yielding 
more light, however, than pure hydrogen gas, which it otherwise re- 
sembles. Animals introduced into it, instantly cease to breathe. 

It consists of one equivalent of carbon (C) united to two of hydrogen 
(•2H or H2), and is represented by CHj. When burned in the air or 



50 PROPERTIES OF AxMMONIA. 

in oxygen gas, the carbon it contains is converted into carbonic acid 
(COo), and the hydrogen into wafer (HO). 

Like oxalic acid this gas cannot, by any known process, be produced 
from the direct union of the carbon and hydrogen of which it consists. 
It is readily obtained, however, by heating acetate of potash in a retort, 
with an equivalent proportion of caustic baryta. [Acetate of potash is 
])repared by pouring vinegar (acetic acid) on common pearlash and 
evaporating the solution.] 

In nature it is largely evolved in coal mines, and is the principal com- 
bustible ingredient in those explosive atmospheres which so frequently 
cause disastrous accidents in mining districts. 

This gas is also given off along with carbonic acid during the fermen- 
tation of compost heaps, or of other large collections of vegetable mat- 
ter. It is said also to be generally present in well manured soils, 
[Persoz, Chimie Moleculaire, p. 547,] and is supposed by many to con- 
tribute in such cases to the nourishment of plants. It is, however, very 
sparingly soluble in water, so that in a state of solution, it cannot enter 
largely into the pores of the roots, even though it be abundantly present 
in the soil. How far it can with propriety be regarded as a general 
source of food to plants, will be considered in the following lecture. 

§ 5. Ammonia, its properties and relations to vegetable life. 

Ammonia is a compound of hydrogen and nitrogen. It is possessed 
of many interesting properties, and is supposed to perform a very im- 
portant part in the process of vegetation. It will be proper, therefore, 
to illustrate its nature and properties with considerable attention. 

Ammonia, like the nitrogen and hydrogen of which it is composed, is 
a colourless gas, but, unlike its elements, is easily distinguished from 
all other gaseous substances by its smell and taste. 

It possesses a powerful ])eneirating odour (familiar to you in the smell 
of hartshorn and of common smelling salts), has a burning acrid alka- 
line* taste, extinguishes a lighted taper as hydrogen and nitrogen do, but 
does not itself take fire like the former. It instantly suflfbcates animals, 
kills living vegetables, and gradually destroys the texture of their parts. 

It is absorbed in large quantities by porous substances, such as char- 
coal — which, as already stated, absorbs 95 times its own bulk of am- 
nioniacal gas. Porous vegetable substances in a decaying state likewise 
absorb it. Porous soils also, burned bricks, burned clay, and even com- 
mon clay and iron ochre, which are mixed together on the surface of 
most of our fertile lands — all these are capable of absorbing or drinking 
in, and retaining within their pores, this gaseous substance, when it hap- 
pens to be brought into contact with them. 

But the quantity absorbed by water is much greater and more sur- 
prising. If the mouth of a bottle filled with this gas be immersed in 
water, the latter will rush up and fill the bottle almost instantaneously; 
and if a sufficient supply of ammonia be present, a given quantity of 
water will take up as much as 670 times its bulk of the gas. 

This solution of ammonia in water is the spirit of hartshorn of the 
shops. When saturated [that is, when gas is supplied till the water re- 

* The term alknUne, as applied to taste, will be best iitifterstood by describing it as a taste 
similar to thai of the common soda and pearlash of (he shops. 



ITS COMBINATION WITH ACIDS. 51 

fuses to take up any more,] it is lighter than pure water, [its specific 
gravity is 0*875, water being I,] has the pungent penetrating odour of the 
gas, and its hot, burning, alkaline taste — is capable of blistering the 
skin, and decomposing or destroying the texture of animal and vegeta- 
ble substances. 

You will remark here the effect which combination has in investing 
substances with new characters. The two gases hydrogen and nitrogen, 
themselves without taste or smell, and absorbed by water in minute 
quantity only, form by their union a compound body remarkable both 
for taste and smell, and for the rapidity with which water absorbs it. 

Ammonia possesses also alkaline properties,* it restores the blue 
colour of vegetable substances that have been reddened by an acid, and 
it combines with acid substances to form salts. 

Among gaseous substances, therefore, there are some which, like car- 
bonic acid, have a sour taste and redden vegetable blues ; others which, 
like ainmonia, have an alkaline taste and restore the blue colour; and 
a third class which, like oxygen, hydrogen, and nitrogen, are destitute of 
taste and do not affect vegetable colours. These last are called nen^ 
tial or indifferent substances. 

Ammonia, as above stated, combines with acids and forms salts, 
which at the ordinary temperature of the atmosphere are all solid sub- 
stances. Hence if carbonic acid gas be mixed with ammoniacal gas, 
a white cloud is formed consisting of minute particles of solid carbonate 
of ammonia — the smelling salts of the shops. Hence also a feather 
dipped into vinegar or dilute muriatic acid (spirit of salt), and then in- 
troduced into ammoniacal gas, forms a similar white cloud, and be- 
comes covered with a white down of solid acetate or ofinuriaie of ammonia 
(sal ammoniac). The same appearance is readily seen by holding the 
feather to the mouth of a bottle containing hartshorn (liquid ammonia), 
from which ammoniacal gas continually escapes, and by its lightness rises 
into the air, and thus comes in contact with the acid upon the feathers. 

The fact of the production of a solid body by the union of two gases 
(ammonia and carbonic or muriatic acid gases) is one of a very inter- 
esting nature to the young chemist, and presents a further illustration 
of the changes resulting from chemical- combination as explained in 
the previous lecture. 

Ammonia is little more than half the weight of common air, [more 
nearly three-fifths, its specific gravity being 0*59, that of air being 1,] 
hence when liberated on the earth's surface it readily rises into and 
mingles with the atmosphere. It consists of hydrogen and nitrogen 
united together in the proportion of three equivalents of hydrogen (3H 
or H3) and one of nitrogen (N), [see Lecture H,] and hence.it is re- 
presented by the symbol (N -f 3H), or more shortly by NH3. 100 
parts by weight contain 82i of nitrogen and 17i of hydrogen, [correct- 
ly 82-545 and 17-455 respectively.] 

In nature, ammonia exists in considerable quantity. It is widely, 

' In the previous lecture, the term acid was explained as applying to substances possess- 
ed of a sour taste, and capable of reddening vegetable blues or combining with basts (pot- 
ash, soda, magnesia, &c.) to form salts ; alkalies are such as possess an alkaline faste (see 
previous Note), restore the blue colour to reddened vegetable substances, or combine with 
adds to form salts. Of salts, nitrate of soda, saltpetre (nitrate of potash), and glauber salts 
(sulphate of soda), are examples. 



62 ITS EXISTENCE IN NATURE, AND SPECIAL PROPERTIES. 

almost universally, diffused, but is not known to form large deposits on 
any part of the earth's surface, or to enter as a constituent into any 
of the great mineral masses of which the crust of the globe is com- 
posed. It exists most abundantly in a state of combination — in the 
forms, for example, of muriate (sal ammoniac), of nitrate, and of carbon- 
ate of ammonia. It frequently escapes into the atmosphere in an un- 
combined state, especially where animal matters are undergoing decay, 
but it rarely exists in this free state for any length of time. It speedily 
unites with the carbonic acid of the air, with one or other of the numer- 
ous acid vapours which are continually rising from the earth, or with 
the nitric acid which is formed at the expense of the nitrogen and oxy- 
gen of which the atmosphere consists. 

The influence of ammonia on vegetation appears to be of a very 
powerful kind. It seems not only to promote the rapidity and luxu- 
riance of vegetation, but to exercise a powerful control over the func- 
tions of vegetable life. In reference to the nature and extent of this 
action, into which we shall hereafter have occasion to inquire, there 
are several special properties of ammonia which it will be of impor- 
tance for us previously to understand. 

1°. It has a powerful afTmity* for acid substances. Hence the 
readiness with which it unites with acid vapours when it rises into the 
atmosphere. Hence also when formed or liberated in the soil, in the 
fold-yard, in the stable, or in compost heaps, it unites with such acid 
substances as may be present in the soil, &c. and forms saline com- 
pounds or salts. All these salts appear to be more or less influential in 
the processes of vegetable life. 

2°. Yet this affinity is much less strong than that which is exhibited 
for the same acids by potash, soda, lime, or magnesia. Hence if any 
of these substances be mixed or brought into contact with a salt of am- 
monia, the acid of the latter is taken up by the potash or lime, while 
the ammonia is separated in a gaseous state. Thus when sal ammo- 
niac in powder is mixed with twice its weight of quick-lime, amraoni- 
acal gas is liberated in large quantity. This is the method by which 
pure, ammonia is generally prepared ; and one of the many functions 
performed by lime when employed for the improvement of land, espe- 
cially on soils rich in animal and vegetable matter, is that of decompo- 
sing the salts, especially the organic salts, of ammonia, — as will be 
more fully explained when we come to treat at length of this important 
part of agricultural practice. f 

3°. The salts which ammonia forms with the acids are all, like am- 
monia itself, very soluble in water. Hence two consequences follow. 
First, that which rises into the air in the form of gas, and there com- 
bines with the carbonic or other acids, is readily dissolved, washed out 

' By affinity is meant the temiency which bodies have to unite and to remain united or 
combined. Thus ammonia forms a solid substance with the vapour of vinegar the moment 
the two substances come into contact; they have, therefore, a sUong tendency to unite, or 
an affinity for each other. 

t See Lecture XVI. '■'■On the use of lime." Owing to this property the action of lime upon 
compost heaps is often injurious, by causing the evolution of the ammonia produced during 
the decomposition of the animal matters they contain. This escape of ammonia, even 
when imperceptible by the sense of smell, is easily delected by holding over the heap a fea- 
ther dipped in vine;;ar or in spirit of salt (muriatic acid), when white fumes are immediate- 
ly perceived if ammonia be present. 



DECOMPOSES GYPSUM. 53 

and brought to the earth ae;ain by the rains and dews ; so that at the 
same lime the air is purified for the use of animals, and the ammo- 
nia brought down for the use of plants. And second, whatever salts of 
ammonia are contained in the soil, being dissolved by the rain, are in 
a condition to be taken up, when wholesome, by the roots of plants; or 
to be carried off by the drains when injurious to vegetation. 

4°. I have already alluded to the fact of this gas being absorbed by 
porous substances, and to its presence, in consequence, in porous soils, 
and in burned bricks and cla\'. AVith the purer kinds of unburned 
clay, however, and with the oxide of iron contained in red (or ferrugi- 
nous)* soils, ammonia is supposed to form a chemical compound of a 
weak nature. In consequence of its affinity or feeble tendency to com- 
bine with these substances, they attract it from the air, and from decay- 
ing animal or vegetable matters, and retain it more strongly than many 
porous substances can, — yet with a sufficiently feeble hold to yield it 
up, readily as is supposed, to the roots of plants, when their extremities 
are pushed forth in search of food. In this case the carbonic, acetic, 
and other acids given off, or supposed to be given off by the roots, exer- 
cise an influence to which more particular allusion will be n^ade here- 
after. 

6"^. In the state of carbonate it decomposes gypsum, forming carbon- 
ate of lime (chalk) and sulphate of ammonia. f The action of gypsum 
on grass lands, so undoubtedly beneficial in many parts of the world, 
has been ascribed to this single property; it being supposed that llie 
sulphate of ammonia formed, is peculiarly favourable to vegetation. 
This question will come properly under review hereafter. I may here, 
however, remark that if this be the sole reason for the efficiency of gyp- 
sum, its application ought to be l)eneficial on all lands not already 
abounding either in gypsum or in sulphate of ammonia. J But if tlie 

* Soila reddened by the presence of oxide of iron. 

t Gypsum is sulphate of lime — cortsisting of sulphuric acid (oil of vitriol) and quicklime. 
Carbonate of ammonia consists of carbonic acid and ammonia. When tlie two substances 
act upon each oth^r in a moist state — the two acids cliani^e places— the sulphuric acid, as it 
were, preferring the ammonia, the carbonic acid the lime. 

X Liebig says — "the striking fertility of a meadow on which gypsum i.s strewed depends 
only on its fixing in the soil the ammonia of the atmosphere, which would otherwise be vola- 
tilized with the water which evaporates." — Organic Chemistry applied to Agriculture, p. 88. 
[By fixing is meant the forming of sulphate with the ammonia. Rain water is supposed to 
bring down with it carbonate of annnunia (common smelling salts), which acts upon the sul- 
phateoflifne (i!.ypsum) in such a way that sulphate of ammnnia cin(\ cnrfwnate of li?ne are 
produced. The carbonate of ammonia readily volatilizes or rises again into the air, the sul- 
phate does not — hence the use of the word^x.] 

When we come to consider the subject of mineral manures in general, we shall study 
more in detail the specific action of gypsum in promoting vegetation — a very simple calcula- 
tion, however, will serve to shew that the above theory of Liebig is far from aflfordinga satis- 
factory explanation of all the phenomena. 

Supposing the gypsum to meet with a sufficient supply of ammonia in the soil, and that it 
exercises its full influence, 100 lb=!. of common U7ihurned gy\)sum will fix or form sulphate 
with nearly 20 lbs. of ammonia containing )6^1bs. of nitrogen. One hundred weight, there- 
fore, (112 lbs.) will form as much sulphate as will contain 22ilbs. of ammonia, and if intix>- 
duced without loss into the interior of plants will furnish them with I8h lbs. of nitrogen. 

1°. In the first volume of British Husbandry, pp. 322, 323, the following experiment is 
recorded : 

Mr. Smith, ofTunstal, near Sittingbourne, top-dressed one portion of a field of red clover 
with powdered gypsum at the rate of five bushels (or four hundred weight") per acre, and 
compared the produce with another portion of the same field, to which no manure had- been 

[' A ton of pure gypsum, when crushed, will yield 2o bushels. It should, however, al« 

wavs be applied by weight.] 



SEED. 


STRAW. 


nrs. lbs. 


cwt. qrs. lbs. 


3 21 


22 3 12 


20 


5 



54 MODE IN WHICH GYPSUM ACTS. 

results of experimental farming in this country are to be trusted, this is 
by no means the case. The action neither of this, nor probably of any 
other inorganic substance applied to the soil, is to be explained by a 
reference in every case to one and the same property only. 

7°. The presence or evolution of ammonia in a soil containing animal 
and vegetable matter in a decaying state, induces or disposes this mat- 
ter to attract oxygen from the air more rapidly and abundantly. The 
result of this is, that organic acid compounds are formed, which combine 

applied. The first crop was cut for hay, and the second ripened for seed. Tlie following 
were the comparative results per acre : 

HAY CROP. 

cwt. 

Gypsumed 60 

Unmanured 20 

Excess of produce . . 40 3 1 17 3 12 

The excess of produce in all the three crops upon the gypsumed land is very large : let us 
calculate how much nitrogen this excess would contain. In a previous lecture (II. p. 30) it 
was stated as the result of Boussingault's analyses, tliat dry clover seed contained 7 per 
cent, of nitrogen, and the same expei'imenter found in the hay of red clover 1^ per cent, (or 
70 and 15 lbs. respectively in 1000.) 

The seed as it was weighed by Mr. Smith would still contain one-ninth of its weight of 
water, and, consequently, only 6>3rd per cent, of nitrogen, [see Lecture II. p. 30.] Let it 
be taken at 6 per cent, and let the straw be supposed to contain only 1 per cent, of nitro- 
gen, the quantity of this element being found to diminish in the grasses after the seed has 
ripened, and averaging 1 per cent, in the straw of wheat, oats, and barley, the weight of ni- 
trogen reaped in the whole crop will then be as follows : 

1. 40 cwt. of hay (4480 lbs.) at U per cent, of nitrogen, contain 67 lbs. 

2. 85 lbs. of seed at 6 per cent, contain 5 lbs. 

3. 17 cwt. 3 qrs. 12 lbs. or 2000 lbs. of straw at 1 p^r cent, contain 20 lbs. 

Total nitrogen in the excess of crop, 92 lbs. 

But, as above shewn, the five bushels or four cwt. of gypsum could fix only 90 lbs. of am- 
monia containing 74 lbs. of nitrogen, leaving, therefore, 18 lbs. or onefifth of the whole, to be 
derived from some other source. 

Now this result supposes that none of the gypsum or sulphate of ammonia was carried 
away by the rains, but that the whole remained in the soil, and produced its greatest possible 
effect on the clover — and all in one season. 

But the effect of the gypsum does not disappear with the crop to which it is actually ap- 
plied. Its beneficial action is extended to the succeeding crop of wheat, and on grass lands 
the amelioration is visible for a succession of years. If, then, the increased produce of a 
single year may contain more nitrogen than the gypsum can be supposed to yield, this sub- 
stance must exercise some other influence over vegetation than is involved in its supposed 
action on the indefinite (juantity of ammonia in the atmosphere. 

2°. Again, Mr. Barnard, of Little Bordean, Hants, applied 2§ cwt. per acre on two-year 
old sain foin, on a clayey soil. Tlie increased produce of thefirst cutting was a ton per 
acre, and in October fully a ton, the undressed part yielding scarcely any hay at all, while 
the dressed part gave I7 tons. The second year no gypsum was appUed. and the diflference 
is .said to have been at least as great. 

Supposing the increased produce in all to have been 4 tons of hay, and thenilrogen it con- 
tained to have been only one per cent.— the 4 tons (89G0 lbs.) would contain about 90 lbs. of 
nitrogen. But 2^ cwt. would fix only 46 lbs. of nitrogen in the form of ammonia ; and there- 
fore, supposing it to have produced its maximum effect, there remain A^ lbs. or nearly one 
half of the whole, unaccounted for by tlie theory. 

I would not be understood to place absoluie reliance on the results of the above experi- 
ments; but the way in which such results may be easily applied for the purpose of testing 
theoretical views, will, I hope, convince the intelligent practical agriculturist how important 
it i*i that the results of some of the experiments he is every year making should be accu- 
rately determined by weight and measure. By this means data would gradually be accu- 
mulated, on which we might hope to found more unexceptionable explanations of the phe- 
nomena of vegetation, than the results obtained in our laboratories have hitherto enabled 
us to advance. 

In a subsequent note it will be shewn that the mode in which the nitrates of soda and 
potash act— in other words, the theory of their action upon vegetation — may be tested by a 
similar simple calculation, and the importance of precise experimejits made on the falm 
will then still further appear. It is in the hope of imlucmg some of njy readers to make 
comparative trials and publish occM?a/e results, that I have introduced into the Appendix 
(No. I.) an outline of the mode iu whicl» such experiments may most usefully be performed. 



I>rLUKNCE OF AMMOiyiA OVilE PLANTS. 66 

with the ammonia, and form ammoniacal salts.* On the decomposi- 
tion of these salts by lime or otherwise — the organic acids which are se- 
parated from them, are always more advanced towards that state in 
which they again become fit to act as food for plants. 

8°. But the most interesting, and perhaps the most important proper- 
ty of ammonia, is one which I have already had occasion to bring under 
your notice, as possessed by water also, and as peculiarly fitting that 
fluid for the varied functions it performs in reference to vegetable life. 
This property is the ease with which it undergoes decomposition, either 
in the air, in the soil, or in the interior of plants. 

In the air it is diffused through, and intimately mixed with, a large 
excess of oxygen gas. In the soil, especially near the surface, it is also 
continually in contact with oxygen. By the influence of electricity in 
the air, and of lime and other bases in the soil, it undergoes a constant 
though gradual decomposition (oxidation), its hydrogen being chiefly 
converted into water, and a portion of its nitrogen into nitric acid.f 

In the interior of plants this and other numerous and varied decom- 
posilions in all probability take place. 

The important influence which ammonia appears to exercise over the 
growth of plants — the evidence for which I shall presently lay before 
you — is only to be explained on the supposition that numerous transfor- 
mations of organic substances are effected in the interior of living vege- 
tables — which transformations all imply the separation from each other, 
or the re-arrangement of the elements of which ammonia consists. In 
the interior of the plant we have seen that water, ever present in great 
abundance, is also ever ready to yield its hydrogen or its oxygen as oc- 
casion may require, while tliese same elements are never unwilling to 
unite again for the formation of water. So it is, to a certain degree, 
■with ammonia. The hydrogen it contains in so large a quantity is ready 
to separate itself from the nitrogen in the interior of the plant, and, in con- 
cert with the other organic elements introduced by the roots or the leaves, 
to aid in producing the different solid bodies of which the several parts 
of plants are made up. The nitrogen also becomes fixed in the coloured 
petals of the flowers, in the seeds, and in other parts, of which it appears 
to constitute a necessary ingredient — passes off" in the form of new com- 
pounds, in the insensible perspiration or odoriferous exhalations of the 
plant, — or returning with the downward circulation, is thrown off^by the 
root into the soil from which it was originally derived. Much obscurity 
still rests on the actual transformations which take place in the interior 
of plants, yet we shall be able in a future lecture, I hope, to arrive at a 
tolerably clear understanding of the general nature of many of them. 

Such are the more important of those properties of ammonia, to which 
we shall hereafter have occasion to advert. The sources, remote as 
well as immediate, from which plants derive this, and other compounds 
we have described as contributing to the nourishment and growth of 
plants, will be detailed in a subsequent section. 

' Organic ac/rfs generally contain more oxygen in proportion to their carbon and hydro- 
gen, than those which are alkaline or neuhal. 

t It will be remembered that ammonia is represented by NH3, water by HO, and nitric 
acid by NO5. It is easy to see, tlier'efore, how, by means of oxygen, ammonia should be 
converted into water and nitric acid. 



56 PROPERTIES or NITRIC ACID. 

§ 6. Nitric acid, its constitution and properties. 

When the nitre or saltpetre of commerce is introduced into a retort, 
covered with strong sulphuric acid (oil of vitriol*) and heated over a lamp 
or a charcoal fire, red fumes are given off, and a transparent, often 
brownish or reddish li(|uid, distils over, which may be collected in a bot- 
tle or other receiver of glass. This liquid is exceedingly acid and cor- 
rosive. In small quantity it stains the skin and imparts a yellow colour 
to animal and vegetable substances. In larger quantity it corrodes the 
skin, producing a painful sore, rapidly destroys animal and vegetable 
life, and speedily decomposes and oxidizesf all organic substances. 
Being obtained from nitre, this liquid is called nitric acid. It consists of 
nitrogen combined with oxygen, one equivalent of the former (N) being 
united to 5 of the latter (O5), and is represented by NOg. 

This acid contains much oxygen, as its formula indicates, and its ac- 
tion on nearly all organic substances depends upon the ease with which 
it Is decomposed, and may be made to part with a portion of this oxygen. 

In nature, it never occurs in a free state ; but it is found in many in- 
tertropical (hot) countries in combination with potash, soda, and lime — in 
the stare of nitrates. It is an important character of these nitrates that, like 
the salts of ammonia, they are all very soluble in water. Those of so- 
da, lime, and magnesia attract moisture from the air, and in a damp at- 
mosphere gradually assume the liquid form. 

Saltpetre is a compound of nitric acid with potash (nitrate of potash). 
It is met with in the s^urface soil of many districts in Upper India, and 
is separated by washing the soil and subsequently evaporating (or boil- 
ing down) the clear li(|uid thus obtained. When pure, it does not be- 
come moist on exposure to the air. It is chiefly used in the manufac- 
ture of gunpowder, but has also been recommended and frequently and 
successfully tried by the practical husbandman, as an influential agent 
in promoting vegetation. 

In combination with soda, it is found in deposits of considerable thick- 
ness in the district of Arica in Northern Peru, from whence it is im- 
ported into this country, chiefly for the manufacture of nitric and sulphu- 
ric acids. More recently its lower price has caused it to be extensively 
employed in husbandry, especially as a top-dressing for grass lands. 
Like the acid itself, these nitrates of potash and soda, when present in 
large quantities, are injurious to vegetation. This is probably one cause 
of the barrenness of the district of Arica in Peru, and of other countries, 
where in consequence of the little rain that falls, the nitrous incrusta- 
tions are accumulated upon the soil. In small quantity they appear to 
exercise an important and salutary influence on the rapidity of growth, 
and on the amount of produce of many of the cultivated grasses. This 
salutary influence is to be ascribed, either in whole or in part, to the 
constitution and nature of the nitric acid which these salts contain. It 

* Sulphuric acid is a compound of oxygen and sulphur, which is prepared by burning sul- 
phur wth certain precautions in large leaden chambers. It is also obtained directly by dis- 
tillinii green vitriol (sulphate of iron) at a high temperature in an iron still — hence its name oil 
of vitriol. It is a heavy, oily, acid, and remarkably corrosive liquid. In a concentrated state 
it is exceedingly destructive both to animal and to vegetable life. 

t When a substance combines with oxygen^ either in consequence of exposure to the air 
or in any otlier circumstances, it is said to become oxidized. 



qUESTlONS TO BE CONSIDERED. 57 

is chiefly ^vith a view to the explanation I shall hereafter attempt to 
give of the nature of this salutary action, that I have thought it neces- 
sary here to make you acquainted with this acid compound of nitrogen 
and oxygen, in connection with the alkaline compound (ammonia) of ihe 
same gas with hydrogen. 

Having thus shortly described both the organic elements themselves, 
and such chemical compounds of these elements as appear fo be most 
concerned in promoting the growth of plants, we are prepared for enter- 
ing upon ihe consideration of several very important questions. These 
questions are — 

1°. From what source do plants derive the organic elements of which 
they are composed ? 

2°. In what form do plants take them up— or what proof have we 
that the com pounds above described really enter into plants? 

3°. By what organs is the food introduced into the circulation of 
plants? In consequence of what peculiar structure of these several 
parts are plants enabled to take up the compounds by which they appear 
to be fed ; and what are the functions of these parts, by the exercise of 
which the food is converted and appropriated to their own sustenance 
and further growth ? 

4*^. By what chemical changes is the food assimilated by plants, that 
is — after being introduced into the circulation, through what series of 
chemical changes does it pass, before it is converted by the plant into 
portions of its own substance ? 

5°. By what natural laws or adaptations is the supply of those com- 
pounds, which are the food of plants, kept up ? Animals are supported 
by an unfailing succession of vegetable crops, — by the operation of what 
invariable laws is food continually provided for plants ? 

These questions we shall consider in succession. 



LECTURE IV. 

Source of the organic elements of plants — Source of the carbon — Form in which it enters 
into Ih'e circulation of plants — Source of the hydrogen — Source of the oxygen — Source of 
the nitrogen — Form in which nitrogen enters into the circulation of plants — Absorption of 
ammonia and nitric acid by plants. 

The first of the series of questions stated at the close of the preceding 
lecture, regards the source from which plants derive the organic ele- 
ments of which they are composed. They are supported, it is obvious, 
at the conjoined expense of the earth and the air — how much do they 
owe to each, and for which elejiients are they chiefly and immediately 
indebted to the soil, and for which to tlie atmosphere ? We must first 
consider the source of each element separately. 

§1. Source of the carbon of plants. 

We have already seen reason to believe that carbon is incapable of 
entering directly, in its solid state, into the circulation of plants. It is 
generally considered, indeed, that solid substances of every kind are un- 
fit for being taken up by the organs of plants, and that only such as are 
in the liquid or gaseous state, can be absorbed by the minute vessels of 
which the cellular substances of the roots and leaves of plants are com- 
posed. Carbon, therefore, must enter either in the gaseous or liquid 
ibrm, but from what source must it be derived ? There are but two 
sources from which it can be obtained, — the soil in which the plant 
grows — and the air by which its stems and leaves are surrounded. 

In the soil much vegetable matter is often present, and the farmer 
adds vegetable manure in large quantities with the view of providing 
food for his intended crop. Are plants really fed by the vegetable mat- 
ter which exists in the soil, or by the vegetable manure that is added to 
it? 

This question has an important practical bearing. Let us, therefore, 
submit it to a thorough examination. 

1°. We know, from sacred history, what reason and science concur 
in confirming, that there was a time when no vegetable matter existed 
in the soil which overspread the earth's surface. The first plants must 
have grown without the aid of either animal or vegetable matter — that 
is, they must have been nourished from the air. 

2°. It is known that certain marly soils, raised from a great depth 
beneath the surface, and containing apparently no vegetable matter, 
will yet, without manure, yield luxuriant crops. The carbon in such 
cases must also have been derived from the air. 

3°. You know that some plants grow and increase in size when sus- 
pended in the air, and without being in contact with the soil. 

You know, also that many plants— bulbous flower roots for example 
— will grow and flourish in pure water only, provided they are open to 
tlie access of the atmospheric air. Seeds also will germinate, and, 
when duly watered, will rise into plants, though sown iu substances 
that contain no trace of vegetable matter. 



•\VHE3^Cfi 1»LANT3 DERIVE THEIR CARBON. 59 

Thus De Saussure found that two beans, when caused to vegetate in 
the open air on pounded flints, doubled the weight of the carbon they 
originally contained. 

Under similar circumstances Boussingault found the seeds of trefoil 
increased in weight 2i times, and wheat gave plants equal in weight, 
when dry, to twice that of the original grains, [ Ar>n. de Chim. et de Phys. 
Ixvii., p. 1.] The source of the carbon in all these cases cannot be 
doubted. 

4°. When lands are impoverished, you lay them down to grass, and 
the longer they lie undisturbed the richer in vegetable matter does the 
soil become. When broken up, you find a black fertile mould where 
little trace of organic matter had previously existed. 

The same observation applies to lands long under wood. The vege- 
table matter increases, the soil improves, and when cleared and plough- 
ed it yields abundant crops of corn. 

Do grasses and trees derive their carbon from the soil ? Then, how, 
by their growth, do they increase the quantity of carbonaceous matter 
which the soil contains ? It is obvious that, taken as a whole, they 
must draw from the air not only as much as is contained in their own 
substance, but an excess also, which they impart to the soil. 

5°. But on this point the rapid growth of peat may be considered as 
absolutely conclusive. A tree falls across a little running stream, dams 
up the water, and produces a marshy spot. Rushes and reeds spring 
up, mosses take root and grow. Year after year new shoots are sent 
forth, and the old plants die. Vegetable matter accumulates ; a bog, 
and finally a thick bed of peat is formed. 

Nor does this peat form and accumulate at the expense of one spe- 
cies or genus of plants only. Laiitude and local situation are the cir- 
cumstances which chiefi}'' effect this accumulation of vegetable matter 
on the soil. In our own country, the lowest layers of peat are formed 
of aquatic plants, the next of mosses, and the highest of heath. In 
Terra del Fuego, "nearly every patch of level ground is covered by 
two species of plants [asteiia pumila of Brown, and donatia magellau' 
ica), which, by their joint decay, compose a thick bed of elastic peat." 
" In the Falkland Islands, almost every kind of plant, even the coarse 
grass which covers the whole surface of the island, becomes converted 
into this substance."* 

Whence have all these plants derived their carbon ? The quantity 
originally contained in the soil is, after a lapse of years, increased ten 
thousand fold. Has dead matter the power of reproducing itself? 
You will answer at once, that all these plants must iiave grown at the 
expense of the air, must have lived on the carbon it was capable of af- 
fording them, and as they died must have left this carbon in a state un- 
fit to nourish the succeeding races. 

This reasoning appears unobjectionable, and, from the entire group of 
facts, we seem justified in concluding that plants every where, and 
under all circumstances, derive the whole of their carbon from the at- 
mosphere. 

• Dancin's Researches in Geology and Natural History^ pp. 349-fJO. Dr. Gei-ville informs 
me that the asteiia approaches more nearly to the juaceae or rush tribe, and the donatia to our 
tufled saxlfratfe?, than to any other Bdlisb plants. 



60 THE VEGETABLE MATTER OF THE SOIL. 

In certain extreme cases, as in those of plants growing in the air and 
in soils perfectly void of organic matter, this conclusion must be abso- 
lutely true. The phenomena admit of no other interpretation. But is 
it as strictly true of the more usual forms of vegetable life, or in the or- 
dinary circumstances in which plants grow spontaneously or are culti- 
vated'^ by the art of man ? Has the vegetable matter of the soil no 
connection with the growth of the trees or herbage ? — does it yield them 
no regular supplies of nourishment ? Does nature every where form a 
vegetable mould on which her wild flowers may blossom and her pri- 
meval forests raise their lofty heads ? Has the agricultural experience 
of all ages and of all countries led the practical farmer to imitate nature 
in preparing such a soil ? Does nature work in vain ? — is all this ex- 
perience to be at once rejected ? * 

While we draw conclusions, legitimate in kind, we must be cautious 
how, in degree, we extend them beyond our premises. 

The consideration of one or two facts will shew that our general con- 
clusion must either be modified or more cautiously expressed. 

1°. It is true that plants will, in certain circumstances, grow in a soil 
containing no sensible quantity of organic matter — but it is also true, 
generally^ that they do not luxuriate or readily ripen their seed in such a 
soil. 

2°. It is consistent with almost universal observation, that the same 
soil is more productive when organic matter is present, than when it is 
wholly absent. 

3°. That if the crop.be carried off a field, less organic matter is left 
in the soil than it contained when the crop began to grow, and that by 
constant cropping the soil is gradually exhausted of organic matter. 

Now it must be granted that tillage alone, without cropping, would 
gradually lessen the amount of organic matter in the soil, by continually 
exposing it to the air and hastening its decay and resolution into gaseous 
substances, which escape into the atmospliere. But two years' open 
fallow, with constant stirring of the land, will not rob it of vegetable 
matter so effectually as a year of fallow succeeded by a crop of wheal. 
Some of the vegetable matter, therefore, which the soil contained when 
the seed was sown, must be carried off the field in the crop. 

The conclusion therefore seems to be reasonable and legitimate, that 
the crop which we remove from a field has not derived all its carbon di- 
rectly from the air — but has extracted a portion of it immediately from 
the soil. It is to supply this supposed loss, that the practical farmer 
finds it necessary to restore to the land in the form of manure — among 
other substances — the carbon also of which the straw or hay had robbed 
the soil. 

But how is this reconcileable with our previous conclusion, that the 
whole of the carbon is derived from the air ? The difficulty is of easy 
solution. 

A seed germinates in a soil in which no vegetable matter exists ; it 
sprouts vigorously, increases then slowly, grows languidly'- at the expense 
of the air, and the plant dies stunted or immature. But in dying it im- 
parts vegetable matter to the soil, on which the next seed thrives better 
— drawing support not only from the air, but by its roots from the soil 
also. The death of this second plant enriches the soil further, and thus, 



i 



HOW THE VEGETABLE MATTER INCREASES. 61 

while each succeeding plant is partly nourished by food from the earth, 
yet each, when it ceases to live, imparts to the soil all the carbon which 
during its life it has extracted from the air. Let the quantity which 
each plant thus returns to the«soil, exceed what it has drawn from it by 
only one ten-thousandth of the whole, and — unless other causes inter- 
vene — the vegetable tnalter in the soil must increase. 

Thus while it is strictly true that the carbon contained in all plants 
has been originally derived from the air, it is not true that the whole of 
what is contained in any one crop we raise, is directly derived from the 
atmosphere — the proportion it draws from the soil is dependent upon nu- 
merous and varied circumstances. 

The history of vegetable growth, therefore — in so far at least as the 
increase of the carbon is concerned — may be thus simply stated : 

1°. A plant grows partly at the expense of the soil, and partly at that 
of the air. When it reaches maturity, or when winter arrives, it dies. 
The dead vegetable matter decays, a part of it is resolved into gaseous 
matter and escapes into the air, a part remains and is incorporated with 
the soil. If that which remains be greater in quantity than that which 
the plant in growing derived from the soil, the vegetable matter will in- 
crease; if less, it will diminish. 

2°. In warm climates the decay of dead vegetable matter is more 
rapid, and, therefore, the portion left in the soil will be less than in 
more temperate regions — in other words, the vegetable matter in the 
soil will increase less rapidly — it may not increase at all. 

3°. As we advance into colder countries, the decay and disappearance 
of dead vegetable matter, in the form ofgaseous substances which escape 
into the atmosphere, become more slow — till at length, between the par- 
allels of 40° and 45°, it begins to accumulate in vast quantities in favour- 
able situations, forming peat bogs of greater or less extent. While the 
living plant here, as in warm climates, derives carbon both from the 
earth and from the air, the dead plant, during its slow and partial decay, 
restores little to the atmosphere, and therefore adds rapidly to the vege- 
table matter of the soil. 

4°. Again, in one and the same climate, the decay of vegetable mat- 
ter, and its conversion into gaseous substances, is more rapid in propor- 
tion to the frequency with which it is disturbed or exposed to the action 
of the sun and air. Hence this decay may be comparatively slow in 
shady woods and in fields covered by a thick sward of grass; and in such 
situations organic matter may accumulate, while it rapidly diminishes 
in an uncovered soil, or in fields repeatedly ploughed and subjected to 
frequent cropping.* 

Being thus fitted, by nature, to draw their sustenance — now from the 
earth, now from the air, and now from both, according as they can most 
readily obtain it — plants are capable of living, — though rarely a robust 
life, — at the expense of either. The proportion of their food which they 
actually derive from each source, will depend upon many circumstan- 
ces — on the nature of the plant itself — on the period of its growth — on 
the soil in which it is planted — on the abundance of food presented to 

* In removing a crop we take away both what the plants have received from the earth and 
what they have absorbed from the air — the materials, in short, intended by nature to reetore 
the loss of vegetable matter arising from the natural decaj. 
6 



^wi 



62 PLANTS PARTLY SUPPORTED BY THE AIR AND BV THE SOIL. 

cither extremity — on the warmth and moisture of the climate — on the du- 
ration and intensity of the sunshine, and other circumstances of a similar 

kind so that the only general law seems to be, that, like animals, plants 

have also the power of adapting themselves, to a certain extent, to the 
conditions in which they are placed ; and of supporting life by the aid of. 
such sustenance as may be within their reach. ^ ^ 

Such a view of the course of nature in ihe vegetable kingdom, is con- 
sistent, I believe, with all known facts. And that ihe Deity has bounti- 
fully fitted the various orders of plants — with which the surface of the 
earth is at once beautified and rendered capable of supporting animal 
life — to draw their nourishment, in some spots more from the air, in oth- 
ers more from the soil, is only in accordance with the numerous provisions 
we everywhere perceive, for the preservation and continuance of the 
present condition of things. 

By taking a one-sided view of nature, we may arrfve at startling 
conclusions — correct, if taken as partial truths, yet false, if advanced a-ii 
general propositions — and fitted to lead into error, such as have not the- 
requisite knowledge to enable them to Judge ft)r themselves — or such as, 
doubtful of their own judgment, are willing toyield assent to the author- 
ity of a name. 

Of this kind appears, at first sight, to be the statement of Liebig, that 
"when a plant is quite matured, and when the organs by which it ob- 
tains food from the atmosphere are formed, the carbonic acid of the soil 
is no further required" — and that, "during the heat of summer it derives; 
its carbon exclusively from the atmosphere." — [Organic Chemistry ap- 
plied to Agriculture, p. 48.] 

A little consideration will shew us that, while the proposition contained 
in the former quotation may be entertained and advanced as amatter of 
opinion — the latter is obviously incorrect. In summer, when the sun 
shines the brightest, and for the greatest number of hours, the evapora- 
tion from the leaves of all plants (theii' insensible perspiration) is the 
greatest — the largest suppl}'' of water, therefore, must at this season be 
absorbed by the roots, and transmitted upwards to the leaves. — [Lindley's 
Theory of Horticulture, p. 46.] — But this water, before it enters the roots, 
has derived carbonic acid and other soluble substances from the air and 
from the soil, in as large qiiantity at tliis period as at any other during 
the growth of the plant; and these substances it will carry with it in its 
progress through the roots and the stem. 

Are the functions of the root changed at this stage of the plants' 
growth ? Do they now. absorb pure water only, carefully separating and 
refusing to admit even such substances as are held m solution? Or 
do the same materials which minister to the growth of the plant in its 
earlier stages, now pass upwards to the leaf and return again in the- 
course of the circulation unchanged and unemployed, to be again re- 
jected at the roots ? Does all this take place in the height of summer, 
while the plant is still rapidly increasing in size ? The opinion is nei- 
ther supported by facts nor consistent with analogy. 

But such an opinion, — however the words above quoted may mislead' 
some, — is not Intended to be advanced by Liebig; for, in the 'following 
page he says, that " the power which roots possess of taking up nourish- 
ment does not cease so long as nutriment is present." In summer, 



1 



LEAVES AND ROOTS ABSORB CARBONIC ACID. 63 

therefore, as well as in spring or in autnmn, the plant must be ever ab- 
sorbing nourishment by these roots, if the soil is capable of afTording it— 
and thus, in the general vegetation of the globe, the increase of carbon 
in growing plants must, at every season of the year, be partly derived 
from the vegetable matter of the soil in which they grow. 

§ 2. Form in which carbon enters into the circulation of plants. 

Supposing it to be established that the whole of the carbon contained 
in plants has originally been derived from the air — we have only to in- 
quire in what state this element exists in the atmosphere, in order to 
satisfy ourselves as to the form of combination in which it is and has 
been received into the circulation of plants. In considering the consti- 
tution of the atmosphere in the preceding lecture, it was stated that car- 
bonic acid, a compound of carbon and oxygen, is always present in it— 
and that, though this gas is diffused through the air in comparatively 
small quantity only, yet it is everywhere to be detected, — while no 
other compound of carbon is to be found in it in any appreciable quanti- 
ty. We must conclude, therefore, that from this gaseous carbonic acid 
the whole of the carbon contained in plants has been jrrimarily derived. 
This conclusion is confirmed by the observation so frequently made, 
that the leaves of plants in sunshine absorb carbonic acid, and that 
plants die in an atinosphere from which this gas is entirely excluded. 

But we have seen reason to believe that, under existing circumstan- 
ces, plants also extract a portion of the carbon they contain from the 
soil in which they grow. In what state or form of combination do the 
roots absorb carbon ? 

The most abundant product of the decay of vegetable matter in the 
soil, is the same carbonic acid which plants inhale so largely from the 
atmosphere by their leaves. In a soil replete with vegetable matter, 
therefore, the roots are surrounded by an atmosphere more or less 
charged with carbonic acid. Hence if they are capable of inhaling 
gaseous substances, this gas will enter the roots in the aeriform state — if 
not, it must enter in solution in the water, which the roots drink in so 
largely, to su[)ply the constant waste caused by the insensible perspira- 
tion of the leaves. 

During the early fermentation of artificial manures there is also de- 
veloped in the soil a variable proportion of hght carburetted hydrogen. 
(Lecture III., p. 49), which is supposed by some to enter occasionally 
into the roots. That it does enter, however, is doubtful, — and we are 
safe^ I think, in considering this compound not only as an uncertain 
source of the carbon of plants, but as one from which, in the most fa- 
vourable circumstances, they can derive only a small supply. 

Thus, from the earth as from the air, the most unfailing supply of food 
is the gaseous carbonic acid. 

But as the water passes through the soil it takes up inorganic substan- 
ces — potash, soda, lime, magnesia — and conveys them through the roots 
into the circulation of the plants. Can it refuse to fake up and to perform 
a similar otiice to the soluble organic substances it meets with, as it sinks 
through the soil ? Or do the spongioles of the roots keep a perpetual 
watch over the entering waters, to prevent the introduction of every so- 
luble form of carbon but that of carbonic acid ? Or, supposing such 



64 ROOTS ABSORB ORGANIC SUBSTANCES ALSO 



1 

li 



I 



substances introduced into the interior of the plant, are none of them 
digested there and converted to the general purposes of food ? A state- 
ment of two or three facts will afford a satisfactory reply to these several 
questions. 

1°. When plants are made to grow in infusions of madder the radicle A 
fibres are finked of a red colour. • • 

2^. The flower of a wfiite hyacinth becomes red after a few hours, 
when the earth in which it is planted is sprinkled with the juice of the 
jphyfolaca decandra (BIoi). 

Therefore organic substances can enter into the roots^ and thence into 
the circulation^ of the plant. 

3°. The colour of the madder does not usually extend upwards to 
the leaves and flowers of the plant. 

4°. The colour imparted to the flower of the white hyacinth disap- 
pears in the sunshine in the course of a few days. 

Organic colouring matters, therefore, undergo a chemical change either 
in the stem, in the leaf or in the flower — some sooner, some later — and 
the same is probably the case with most other organic substances which 
gain admission into the interior of plants. 

5°. Sir Humphry Davy introduced plants of mint into weak solutions 
of sugar, gum, jelly, the tanning principle, &c., and found that they 
grew vigorously in all of them. He then watered separate spots of grass 
with the same several solutions, and with common water, and found all 
to thrive more than that to which common water was applied — while 
those treated with sugar, gum, and gelatine grew luxuriantly. — [Davy's 
Agricultural Chemistry, Lecture VI.] 

Therefore different organic substances — being introduced into the cir- 
culation and there changed — are converted by plants into their own sub- 
stance, or act as food, and nourish the jAant. 

"We may consider it, therefore, to be satisfactorily established that, 
while a plant sucks in by irs leaves and roots much carbon in the form of 
carbonic acid, it derives a variable portion of its immediate sustenance 
(of its carbon) from the soluble organic substances that are within reach 
of its roots. 

This fact is never doubted by the practical husbandman. It forms 
the basis of many of his daily and most important operations, while 
the results of these operations are further proofs of the fact. 

The nature of the soluble substances which are formed during the de- 
cay of animal and vegetable substances — and which the roots of plants 
are supposed to take up — will be considered in a subsequent lecture.* 

§ 3. Source of the hydrogen of plants. 

The source of the hydrogen of plants is less doubtful, and will re- 
quire less illustration, than the source of the carbon. This elementary 
substance is not known to exist in nature in an uncombined state, and, 
therefore, it must, like carbon, enter into plants in union with some other 
element. 

1°. Water has been already shewn to consist of hydrogen in combina- 

* This part of the subject might have been discussed here without appearing out of place 
— but it will come in more appropriately, I think, when treating of the nature and mode of 
action of regetabU manitte*. 



SOURCE or THE HYDROGEN OF PLANTS. 65 

tion with oxygen. In the form of vapour, this compound pervades the 
atmosphere, and plays among the leaves of plants, while in the liquid 
state it is diffused through the soil, and is unceasingly drunk in by the 
roots of all living vegetables. In the interior of plants — at least during 
their growth — this water is continually undergoing decomposition, and 
it is unquestionably the chief source of the hydrogen which enters into 
the constitution of their several parts. In explaining the properties of 
water I have already dwelt upon the apparent facility with which its 
elements are capable either of separating from, or of re-uniting to, each 
other, in the vascular system of animals or of plants. The reason and 
precise results of these transformations we shall hereafter consider. 

2°. In light carburetted hydrogen (CH2), given off as already stated 
during the decay of vegetable matter, and said to be always present in 
highly manured soils, this element, hydrogen, exists to the amount of 
nearly one-fourth of its weight. On the extent, therefore, to which this 
gaseous compound gains admission into the roots of plants, will de- 
pend the supply of hydrogen which they are capable of drawing from 
this source. Had we satisfactory evidence of the actual absorption of 
this (marsh) gas by the roots or leaves of plants, in any quantity, we 
should have no difficulty in admitting that plants might, from this source, 
easily obtain a considerable supply both of carbon and of hydrogen. It 
would be also easy to explain how (that is, by what chemical changes,) 
it is capable of being so appropriated. But the extent to which it really 
acts as food to living vegetables is entirely unknown. 

3°. Ammonia is another compound, containing much hydrogen, [its 
formula being NH.3, or one equivalent of nitrogen and three of hydro- 
gen,] which, as I have already stated, exercises a manifest influence on 
the growth of plants. If this substance enter into their circulation in 
any sensible quantity, — if, as some maintain, it be not only universally 
diffused throughout nature, but is constantly affecting, and influencing at 
all times, the universal functions of vegetation — there can be no doubt 
that the hydrogen it contains must, to an equal extent, be concerned in 
the production of the various organic substances which are formed or 
elaborated by the agency of vegetable life. How far this probable in- 
terference of the hydrogen of ammonia with the functions of the vegeta- 
ble organs, will tend to explain or illustrate the influence actually exert- 
ed by this compound, we shall, by and by, more accurately inquire. In 
the mean time,, the quantity of ammonia, which actually enters into the 
circulation of plants in a state of nature, is too little known, and making 
the largest allowance, probably too minute, to permit us to consider it as 
an important source of hydrogen to the general vegetation of the globe. 

4°- The soluble organic substances, which enter into the circulation 
of plants through the roots, as shewn in the preceding section, do not 
consist of carbon and water only, but of combinations of carbon with 
hydrogen and oxygen in various proportions. From these substances, 
therefore, plants derive an uncertam and indefinite supply of hydrogen 
in a state already half-organized, and probably still more easily assimi- 
lated or converted into portions of iheir own substance, than when this 
element is combined with oxygen in the form of water. 

We may, therefore, conclude generally in regard to the source of the 
hydrogen of plants — that though there are undoubtedly several other 



^6 SOURCE OF THE OXYGEN AITD NiTROGEIf . 

forms of combination in which this element may enter inlo their circula- 
tion, in uncertain quantity — yet that all-pervading water is the main 
and constant source from which the hydrogen of vegetable substances is 
derived. 

§ 4. Source of the oxygen of plants. 

We can at once perceive, and without difficulty, the various sources 
of the oxygen of plants ; though it is difficult in this case also to say 
how much they derive from each. 

1°. The water which they imbibe so largely consists in great part of 
oxygen, and is easily decomposed, [eight-ninths of the weight of water 
are oxygen.] This alone would yield an inexhaustible supply. 

2°. The atmosphere contains 21 per cent, of its bulk of oxygen, and 
the leaves of plants in certain circumstances are known to absorb this 
oxygen. The air in which they live, therefore, might be another 
source. 

3°. Carbonic acid contains 72 per cent, by weight of oxygen, and 
this gas is also known to be absorbed in large quantity from the atmos- 
phere by the leaves of plants — while its solution in water is admitted 
readily by the roots. 

From any one of these sources an ample supply of oxygen might 
readily be obtained, and it may be considered as a proof of the vast im- 
portance of this element to the maintenance of animal and vegetable 
life, that it is everywhere placed so abundantly within the reach of 
Jiving beings. It is from the first of these sources, however, from the 
water they contain, that plants are believed to derive their principal 
supply. The reasons on which this opinion is founded will appear 
when we sliall have considered the functions of the several parts of 
plants, and the chemical changes to which the food is subjected in the 
course of the vegetable circulation. 

§ 5. Source of the nitrogen of plants. 

The quantity of nitrogen present in plants is very small, compared 
with that of any of the other elements which enter into their constitu- 
tion. Of this you will be reminded, by a reference to the analyses of 
hay, oats, and potatoes, exhibited in the second lecture (page 30), which 
shew that the nitrogen contained in these several crops, when perfectly 
dried at 240° F., is respectively 1^, 2^, and 1^ per cent. In the state 
in which they are usually given to cattle they contain a still less per 
centage of nitrogen, in consequence of the quantity of water still present 
in them. Thus raw potatoes as they are given to cattle contain only | 
of a per cent, of nitrogen, hay 1^ percent., and oats 1^* per cent., or a 
hundred pounds of each contain 5 ounces, 1 pound 5 ounces, and 1 pound 
14 ounces respectively. 

It would appear at first sight as if this small quantity of nitrogen 
could be cf little importance to the plant, especially since, as we shall 
hereafter see, it does not enter as a constituent into those vegetable sub- 
stances, such as woody fibre, starch, sugar, and gum, which plants pro- 
duce in the greatest abundance, and of which their own stems and 

• 33, 1 29, and 1 87 per cent, —the potatoes containing also 72 per cent, of water, the hay 
14, and the oata 15 per cent. 



QUANTITY OF NITROGEN IN PLANTS. 67 

branches chiefly consist. The same remark, however, applies to this, 
as to many other cases which present themselves to the chemist, during 
his analyses, especially of organized substances, — that those elements 
wliich are present only in small quantity are as necessary — as essential 
— to the constitution of the particular substance in which they occur, as 
other elements are of which they contain much ; and that if these small 
quantities are removed or absent, not only are the physical and chemi- 
cal properties of the substance materially altered, but it is found also to 
exercise a very different influence on animal and vegetable life. This 
latter observation will present itself to you in a very striking light, when 
we come hereafter to study the nutritive properties of the several kinds 
of food by which animals are chiefly supported, — and shall see on what 
elementary body their relative nutritive properties depend, or by the 
amount of which their relative value appears at least to be indicated. 

But a consideration of the absolute quantity of nitrogen contained in 
an entire crop will satisfy you that though small in comparative amount, 
[that is, compared witii the carbon and oxygen which plants contain,] 
this element cannot be without its due share of importance in reference 
to vegetable life. Hay, as above stated, contains, as it is stacked, 1^* 
per cent, of nitrogen, or a ton of hay contains 30 lbs. of this element. A 
good crop of hay, on land which is depastured during the winter, will 
amount to 2 or 24 tonsf per acre. Taking 2 tons as an average, the hay 
from one acre will contain 60 lbs. of nitrogen, or from 100 acres 6000 lbs., 
equal to-2| tons of nitrogen. 

Allowing, therefore, nothing for the aftermath, and supposing the 
other crops to contain no more nitrogen than the hay does, the farmer of 
five hundred acres will annually carry into his stack-yard at least 13 
tons of nitrogen in the form of hay, straw, grain, and other produce. J 

Nature performs all her operations on a large scale, and the quantity 
of materials she employs are large in a corresponding degree. Hence, 
though comparatively small, the nitrogen in vegetable substances is ah- 
solutehj large. You cannot suppose, wlien viewed in this light, that 
nitrogen is an element of little consequence in reference to vegetable 
life ; or that in nature it should be so constantly and universally dif- 
fused without reference to soms important end. If I may be allowed a 
familiar illustration of the mode in which small quantities of matter will 
affect the sensible properties of large masses, I would recall to your 
minds the effects of seasoning upon food, in imparting, when added in 
small quantity only, an agreeable relish to what would otherwise be 

* In different crops of hay Boussingault found in three several years the following pro- 
portions of nitrogen :— 

Hay, as commonly Hay dried at 

stacked. 200° F. 

In IJ>36 118 104 of nitrogen per cent. 

" 1838 1.3 1 15 " " 

" 1839 1-5 1-3 " " 

Aftermath 2i 2 •* " 

t The Rev. Mr. Ogle, of Kirkley, Northumberland, informs me that some of his land 
near the Hall has yielded annually at this rate for 100 years, and without other manure than 
the droppings from the cattle which have fed upon it. 

I This average estimate gives but an inaccurate idea of the quantity actually contained 
In some species of crops. Thus red clover with the aid of gypsum will yield 3 tons of hay 
per acre. This hay contains more than twice the quanfity^of nitrogen (Boussingault) that 
common hay does, hf nee an acre of such hay would contain at least 180 lbs. of nitrogen. 
(See Lecture II., p. 30.) 



68 THE ATMOSPHERE THE PRIMARY SOURCE OP NITROGEN. 

insipid. But I need not dwell on this point, since I shall hereafter have 
occasion to draw your attention to ceriain facts in reference to the con- 
stitution of the atmosphere, which will satisfy you that, hy the agency 
of comparatively feeble causes, gigantic effects are continually produced 
in nature, — and that we can scarcely fall into a graver error in reason- 
ing of natural processes, than by overlooking the agency of forms of mat- 
ter which present themselves to our senses in minute quantity only. In 
reference to insect life this truth has been long established. In the coral 
reefs you are familiar with the wonderful results of tlie persevering la- 
bour of minute animals in one element. When I come to explain the 
nature and origin of soils, I shall have occasion to show that even the 
element on which you labour — the earth, on the cultivation of which 
your thoughts and hands are daily employed — is occasionally indebted 
for some of its most valuable properties to a similar agency, often un- 
seen by you, and though working for your good, unheeded and un- 
thought of. 

Whence, then, is this nitrogen derived by plants? The primary 
source it is not ditficult (o see. We can arrive at it by a train of reason- 
ing similar to that which led us to the atmosphere as the original source 
of the carbon of plants. Nitrogen does not constitute an ingredient of any 
of the solid rocks,* nor do we know any other source than the atmosphere 
from which it can be obtained in very large quantity. It exists, as we 
have seen, in many vegetables, and it is more largely present in animal 
substances, but these organized matters must themselves have drawn 
this element from a foreign source, and the atmosphere is the only one 
from which we can fairly assume it to have been originally derived. 

But though the nitrogen, like the carbon of plants, may thus be traced 
to the atmosphere — as its orginal source — it does not follow that this 
element is either absorbed directly from the air, or, in an uncombined 
and gaseous state. Though the leaves of trees and herbs are continually 
surrounded by nitrogen, the constitution of plants may be unfitted for 
absorbing it by their leaves. The nitrogen may not only require to be 
in a state of combination before it can enter into the circulation, but it 
may also be capable of gaining admission only by the roots. These 
points are considered in the following section. 

§ 6. Form in which the nitrogen enters into the circulation of plants. 

The question as to the form in which nitrogen enters into the circula- 
tion of plants is one which at the present moment engages much attention. 
It will be proper, therefore, to discuss it with considerable care. 

1°. It is considered an essential part of good tillage to break up and 
loosen the soil, in order that the air may have access to the dead vege- 
table matter, as well as to the living roots which descend to considerable 
depths beneath the surface. When thus admitted to the roots, it is-jH^- 
possible that some of the nitroijen of the atmosphere, as well as some of 
its oxygen, may be directly absorbed and appropriated by the plant. 
To what extent this absorption of nitrogen may proceed, however, we 

* Except coal, and coalifself is of vegetable origin. Throughout all rocks in which or- 
ganic remains are found, more or less animal matter containing nitrogen is to be met with, 
but these remains are only accidentally present, and they must have derived their nitrogen 
during life, either directly or indirectly, from the atmosphere. 



RAIN WATER DISSOLVES XT. 



69 



have as yet no experimental results from which we can form any esti- 
mate. Whether it takes place at ail or not, is wholly a matter of opinion. 

2°. The leaves of plants, as will be more fully explained hereafter, absorb 
certain gaseous substances from the atmosphere, and we might, therefore, 
expect that some of: the nitrogen of the air would, by this channel, be 
admitted into their circulation. This view, liowever, is not confirmed 
by any of the experiments hitherto made with the view of investigating 
the action and functions of the leaves.* We are not at liberty, there- 
fore, to assume that any of the nitrogen which plants contain has in this 
way been derived directly from the air. It may be the case ; but it is 
not yet proved. 

3°. There is little doubt, however, that nitrogen enters the roots of 
plants in a state of solution. But the quantity they thus absorb is un- 
certain — it is supposed to be small, and must be variable. 

When water is exposed to the air in an open vessel it gradually ab- 
sorbs oxygen and nitrogen, though, as hks been stated in a "previous lec- 
ture, in proportions different from those in which they exist in the atmos- 
phere. The whole quantity of the mixed gases thus taken up amounts 
to about 4 per cent, of the bulk of the water (Humboldt and Gay-Lus- 
sac), and in rain water about | of the whole consist of nitrogen. One 
hundred cubic inches of rain water, therefore, will carry into the soil 
about 2| inches of nitrogen gas. But in passing through the soil, the 
water meets with other soluble substances befijre it reaches the roots, 
especially the deep-seated roots of plants. It takes up carbonic acid, 
and it dissolves solid substances, and in doing so it is a property of water 
to give off" a portion of the other gases whicli it had previously absorbed 
from the air. 

^ But let us suppose that rain water actually takes to the roots, and car- 
ries with it into the circulation of the plant, 2 per cent, of its bulk of 
nitrogen, and let us calculate how much of the nitrogen it contains a 
crop of hay could in tiiis way derive from the air. 

See subsequent lecture " On the structure and functions of the several parts of plants." 
TIieex|)erinjents above referred to were made irpon plaiit.s growing in close vessels, the 
air contained in which was measured and examined (analysed) both before the plants were 
introduced and after they had been some time in the vessel. In these experiments the 
bulk of the nitrojien present has sometimes been observed to increase, but never to di?>iin- 
ish, in quantity. The conclusion seems satisfactory, that no nitrogen is abstracted directly 
from tlie atmosphere by the leaves of plants. Yet Boussingault* very justly remarks, that 
a dimmntion in the bulk of the nitrogen too small to be detected in the onlinary moiie of 
making these expt^ritnents, would be sufficient to accoiuit fur a considerable portion of Lliat 
comparatively small (juantily of nitrogen which is present in all living plants. While, there- 
fore, we accord their due weight to these researches of the vegetable physiologists, we are 
not to consider them as by any means decisive of tjie question. With this rational and cau- 
tious comdusion, Liebig is not satisfied ; he says, " We have not the slightest reason for be- 
lieving that the nitiog&n of the atmosphere takes part in the processes of assimilation of plants 
ajid animals; on tlie contrary, we know that many pkuits emit tiie tiifrogen which is ab- 
sorbed by their roofs either in the gaseous form or in solution in water." (p. 70.) But if 
they occasionally expire nitrogen by their leave.s why must this nitrogen be exactly that 
portion which has previously been absorbed by the roots in Uie uncombined state, aiid the 
quantity of which is so uncertain and so indefinite! 

[I Boussingault details a series of experiments in the course of which he made peas, tre- 
foil, wheat, and oats, grow in the same pure siUceous sand containing no organic matter, and 
•watered them with the .same distilled water. The absolute (luanlity of nitrogen increased 
sensibly in the peas and trefoil during their growth ; in tlie wlieat and oats no change could 
be detected by analysis. From these resiilts he is inclined to infer that tJie green leaves of 
the former have the power of sensibly absorbing nitrogen from the atmosphere, while those 
of the latter have not this power— at l^ast under the circumstances in which the experi- 
ments were made. This conclusion, however, is not certain, as will presently be shewn. — 
See Ami. de Chini. et de Phrjs. Lxvii. p. 1, and Ixix. p. 353.] 



70 ABSORPTION OF AMMONIA BY PLANTS. 

The quantity of rain that falls at York from the first of March to the 

middle of June — during which time the grass grows and generally ri- 
pens — is about five inches.* On a square foot, therefore, there fall 720 
cubic inches of water, containing 2 per cent, of their bulk, or 14 cubic 
inches of nitrogen, weighing 4} grains. This gives 28 lbs. for the quan- 
tity of nitrogen thus brought to the soil over an entire acre. But if we 
consider how the rain falls in our climate, we cannot suppose the grass 
in a field to absorb by its roots, and afterwards perspire by its leaves, 
more than one-third of the whole. This quantity would carry with it 9 
lbs. of nitrogen into the circulation of the plants — or little more than a 
seventh part of the 60 lbs. which, as we have seen, are taken off the 
field in a crop of hay. 

Such a caJculation as this affords at the best but a very rude approxi- 
mation to the truth — it seems, however, to justify us in concluding that 
plants can derive from the air, and in an uncombined state, only a small 
portion of the nitrogen they are found to contain — and that they proba- 
bly draw a larger supply from certain compounds of this elementary sub- 
stance with hydrogen and oxygen — which are known to come within 
the reach of their roots and leaves. 

The most important of these compounds, and those perhaps the most 
extensively concerned in influencing vegetation, are ammonia and nitric 
acid, the properties of which have been described in the preceding 
lecture. t 

§ 7. Absorption of ammonia hy plants. 

That ammonia enters directly into the circulation of plants is ren- 
dered probable by a variety of considerations. 

1°. Thus it is found to be actually present in the juices of many 
plants. In that of the beet-root, and in those of the birch and maple 
trees, it is associated with cane sugar (Liebig.) In the leaves of the 
tobacco plant, and of scurvy grass, in elder flowers, and in many fungi, 
it is in combination with acid substances, and may he detected by 
mixing their juices with quick-lime. — [Schiibler Agricultur Chemie, 
II., p. 56.] 

2°. Some plants actually perspire ammonia. Among these is the 
Chenopodium Olidum (stinking goosefoot), which is described by Sir 
William Hooker as "giving out a most detestable odour, compared to 
putrid salt fish." In the odoriferous matter given off ammonia is con- 
tained, and may be detected by putting a glass shade over the plant, 
and after a time introducing a feather moistened with vinegar or dilute 
muriatic acid: — [Chevalier Jour, de Pharm. X., p. TOO.] It is also pre- 
sent in the odoriferous exhalations of many sweet-smelling plants and 
flowers. — [Schiibler, I., p. 152.] 

3°. Nearly all vegetable substances, when distilled with water, yield 
an appreciable quantity of ammonia. Thus the leaves of hyssop, and 

* The result of experiments made in 1S34 by Prof. Phillips and Mr, Edward Gray. The 
mean annual fall of rain at York is about 22 inches. — (See fifth Report of the British Associa- 
tion, p. 173.) 

t It will be recollected that ammonia consists of one equivalent of nitrogen (N) united to 
three of hydrogen (H3), being represented by NH3; and that nitric acid consists of one of ni- 
trogen (N) and five of oxygen (Os), its formula being NO3.— See Lecture III., p 34. 



AMMONIA OBTAINED FROM VEGETABLES. 71 

the flowers of the lime tree, yield distilled waters in which ammonia 
can be detected (Schiibler), the seeds of plants thus distilled yield it in 
abundance (Gay-Lussac), and traces of it may be found in most vege- 
table extracts (Liebig). 

4°. Ammonia is also given off, among other products, when wood is 
distilled in iron retorts for the manufacture of pyroligneous acid, and by 
a similar treatment it may be obtained from many other vegetable sub- 
stances. 

The above facts, however, are not to be considered as proofs that am- 
monia enters directly into the circulation of plants either by their roots 
or by their leaves. That which is associated with sugar in the beet, may 
have been formed by the same converting power which, in the interior 
of the plant, has produced the sugar from carbonic acid and water. So, 
that exhaled by the leaves of the goosefoot, which grows in waste places, 
especially near the sea, may have been produced during the upward 
flow of the sap or during its passage over the leaf. And we know that 
the nitrogen does not exist in the state of ammonia in the seeds of plants, 
or in wood, or in coal — though from all of them it may be obtained by 
the processes above described. 

The production of ammonia, by the agency of a high temperature, 
may be illustrated by a very familiar experiment often performed, 
though for a very different purpose. The juice and dried leaf of tobac- 
co contain nitre (nitrate of potash) and a little ammonia. But when 
tobacco is burned, ammonia in sensible quantity is given off along with 
the smoke, chiefly in the state of carbonate of ammonia. This may be 
shown by bringing a lighted cigar near to reddled litmus paper, when 
the blue colour" will be restored ; or to a red ro^e, when the leaves will 
become green ; or to a rod dipped in vinegar or in dilute muriatic acid, 
when a white cloud will appear. — [Runge, Einleitung in die technische 
Chemie, p. 375.] 

In this case a portion of the ammonia given off by the tobacco has 
most probably been formed during the combustion, at the expense of the 
nitrogen contained in the nitrate of potash which is present in the leaf. 

5°. But there are other circumstances which are strongly in favour of 
the opinion, that ammonia not unfrequently does enter, as such, into the 
circulation of plants. ^ 

Thus it is proved, by long experience, that plants grow most rapidly 
and most luxuriantly when supplied with manure containing substances 
of animal origin. These substances are usually applied to the roots or 
leaves in a state of fermentation or decay, during which they always 
evolve ammonia. Putrid urine and night-soil are rich in ammonia, 
and they are among the most efficacious of manures. This ammonia 
is supposed to enter into the circulation of plants along with the water 
absorbed by their roots, and sometimes even by the pores of their leaves. 
We can scarcely be said to have as yet obtained decisive proof that it 
does so enter, but probabilities are strongly in favour of this stapposition ; 
and when we come hereafter, to consider minutely the mode in which it 
is likely to act, when within the plant, we shall find the probabilities 
derived from practical experience to be strengthened by the deductions 
of theory. 

But though the facts so long observed in reference to the action of an- 



72 OTHER IMMEDIATE SOURCES OF NITROGEN. 

imal manures upon vegetation, justify us in believing that ammonia 
actually enters into the roots, and perhaps into the leaves, of plants — we 
ought not hastily to conclude that all the nitrogen which plants are ca- 
pable of deriving from decaying animal matter must enter into their cir- 
culation in the form of ammonia. Other soluble compounds containing 
nitrogen are formed during the decay of animal substances — they ac- 
tually exist largely in the liquid manures of the stable and fold-yard, 
and they can scarcely fail, when applied to the soil, to be to a certain 
extent absorbed by the roots of plants. This urea is a substance con- 
taining much nitrogen, which exists in the urine or excrements of most 
animals, and by its decomposition produces carbonate of ammonia. 
But being very soluble, this substance may enter directly into the roots, 
and may be there decomposed, and made to give up its nitrogen to the 
living plant. To other compound substances of animal origin the same 
observation may apply,* — so that while the fact, that animal manure in 
a state of fermentation i^ very beneficial to vegetation, may be consid- 
ered as rendering it highly probable that the ammonia which such 
manure contains, enters directly and supplies much nitrogen to ths 
growing plants, it must not be entirely left out of view that, in nature, a 
portion of the nitrogen, derived from animal substances, may be ob- 
tained immediately from other compounds in which ammonia does not 
exist. 

To what amount ammonia actually enters into the circulation of 
plants, or how much of the nitrogen they contain it actually supplies, 
we have no means of ascertaining. Were it abundantly present in the 
soil, its great solubilitv would enable it to enter, with the water absorbed 
by the roots, in almost unlimited quantity. In a subsequent section we 
shall consider the conditions under which ammonia is produced in nature, 
the comparative abundance in which it exists on the earth's surface, 
and the extent of the influence it may be supposed to exercise on the 
general vegetation of the globe. 

§ 8. Absorption of nitric acid hy plants. 
1°. That ammonia is actually present in the juices of many living 
vegetables has been adduced, as a kind of presumptive evidence, that 
this compound is directly absorbed by plants. A similar presumption 
is offered in favour of the direct entrance of nitric acid, by its invariable 
presence in combination with potash, soda, lime, or magnesia, in the 
juices of certain common and well known plants. Thus it is said to be 
always contained in the juices of the tobacco plant, of the sunflower, of 
the goosefoot,f and of common borage. The nettle is also said to con- 
tain it, and it has been detected in the grain of barley. t It exists pro- 
bably in the juices of many other plants in which it has not hitherto 

• Thus it may be applied more strongly to the kippuric acid, which exists in the urine of 
the horse, and other herbivorous animals. This acid decomposes naturally into benzoic 
acid and ammonia. The sweet-scented verm.\s.ra.%s {Anthoxanthum Odorutum) by \\\\\i:h 
hay is perfumed, owes its agreeable odour to the presence of this benzoic acid. It may, 
ttierefore, be supposed that, where cattle and horses graze, the grasses actually ab.sorb the 
hippuric acid contained in the urine, which reaches their roots, decompose it as it ascends 
with the sap, appropriate its nitrogen, and exhale the odoriferous benzoic acid. 

t Chenopodium, probably in all the species of this genus.— See Liebig, p. 82. 

t Grisenthwaile (New Theory of Agriculiure, p. 105) says, it is always present in barley in 
the form of uitrate o( soda.—See Appendix. 



ABSORPTION OF NITRIC ACID — ITS EFFECT ON VEGETATION. 73 

been sought for. Were we, therefore, entitled, from fhe mere presence 
of this acid in plants, lo infer that it had really entered by their roots or 
leaves, we should have no hesiiation in drawing our conclusion. But, 
like areimonia, it may have been formed in the interior of the living ve- 
getable ;* and hence the fact of its presence proves nothing in regard to 
the state in which the nitrogen it contains entered into the circulation of 
the plant. 

2°. But nitric acid, like ammonia, exerts a powerful influence on the 
growing crop, whether of corn or of grass. Animal matters, as we have 
seen, give off ammonia during their decay, and manures are rich and 
efficacious in proportion to the quantity of animal manure they contain. 
The crop produced also is valuable and- rich in nitrogen in like propor- 
tion. Therefore, as already stated, it is inferred that ammonia enters 
directly into the living plant, and supplies it with nitrogen. 

The effect of nitric acid is similar in kind, and perhaps equal in de- 
gree. Applied to the young grass or sprouting shoots of grain, it has- 
tens and increases their growth, it occasions a larger produce of grain, 
and this grain, as when ammonia is employed, is richer in gluten, and 
more nutritious in its qualify. f An equal breadth of the same field 
yields a heavier produce, and that produce, weight for weight, contains 
more when saltpetre or nitrate of soda have been applied in certain 
quantities to the young plants which grow upon it. It is reasonable to 
conclude, therefore, that the acid of the nitrates, in some form or other, 

• When the beetroot arrives at maturity, the sugar begins to diminish, and saltpetre or 
other nitrates to be formed, probably at the expense of the ammonia which the juice pre- 
viously contained.— Decroizelles, Jour, de Phar., X., p. 42. 

t The analoffous effects of ammoniacal manures and of the nitrates on the relative quan- 
titles of gluten and starch in grain, are shown by the following experiments : 

Hermbstaedt sowed equal quantities of the same wheat, on equal plots of the same ground, 
•and manured them with equal weights of different manures. Then from 100 parts of each 
sample of grain produced, he obtained starch and gluten in the following proportions : 

Gluten. Starch. Produce. 

Without manure 9-2 667 3 fold. 

With vegetaCle manure (rotted 

potatoe haulm) 96 6594 5 " 

With cow dung 120 623 7 " 

With pigeons' dung 12-2 632 9 " 

With horse dung 13 7 61-64 10 «' 

With goats' dung 329 42 4 12 " 

With sheep dung 329 42 8 12 « 

With dried nighfsoil 33 14 4144 14 « 

With dried ox-blood 34 24 41 3 14 " 

With dried human urine - - - 35 I 393 12 "* 

The manures employed by Hermbstaedt are supposed, during fermentation, to evolve 
more ammonia in the order in which they are here placed, beginning at the top of the list ; 
while the amount and kind of the produce obtained by the use of each, afford the chief evi- 
dence in favour of the opinion that this ammonia actually enters into and yields nitrogen to 
the plant. 

Mr. Hyett found in flour raised on two patches of the same land in Gloucestershire, the 
one dressed with nitrate of soda, the other undresspd, the following proportions : 

Glutpn. Starch. 

Tn the nitrated - - - 2325 49-5 

In the unnitrated - • 19- 55-5 

And Mr. Daubeny, [Three Lectures on Agriculture, p. 76,] in flour from wheat top-dressed 
with saltpetre, found — 

In the nitrated 15 per cent, of gluten. 

In the unnitrated - - - - 13 " " 

These differences are not so striking as in the case of ammonia, but they are precisely 
the same in kind, and lead to the same general conclusion in regard to the nature of the in- 
fluence of the nitrates on vegetation. Accurate and repeated experiments on the precise 
effects of the nitrates are still much to be desired. 

[^ Schiibler. Gi-unds'dtze der AgricuUur Chemie, II. p. 170.] 



74 GEIMERAL CONCLUSIONS. 

is capable of entering into the circulation of living plants — and of yield- 
ing to thera, in whole or in part, the nitrogen they contain. 

But here, again, as in the case of ammonia, we are at fault in regard 
to the quantity of nitrogen which plants in a state of nature actually 
derive from nitric acid or the nitrates. The compounds of this acid with 
potash, soda, lime, and magnesia (the nitrates of these substances), are 
all very soluble in water. The quantity of this fluid, therefore, which 
enters by the roots of plants, could easily convey into their circulation 
far more of these nitrates than would be alone sufficient to supply the 
whole of the nitrogen tiiey require — for the formation of all their parts 
and products. But so it might of ammonia or its salts, as has already 
been shown. I shall hereafter lay before you certain considerations 
which may probably lead us to approximate conclusions in regard to 
the relative influence exercised by these two compounds on the general 
vegetation of the globe. 



Conclusions. — Respecting the form in which nitrogen enters into the 
circulation of plants, we have therefore, I think, fairly arrived at these 
deductions: 

1°. That the nitrogen of the atmosphere may, to a small extent, enter 
directly into the living vegetable either in the form of gas or in solution 
in water, but that supposing nitrogen to be in this way appropriated* by 
the plant, the quantity so taken up could form only a small quantity of 
that which vegetables actually contain.- 

2°. That ammonia is capable of entering into plants in very large 
quantity, and of yielding nitrogen to them, and that in European agri- 
culture, which employs fermenting animal manure as an important 
means of promoting vegetable growth, it does appear to yield to cultiva- 
ted plants a considerable portion of the nitrogen they contain. 

3°. That nitric acid, in like manner, is capable of entering into and 
giving up its nitrogen to plants; and that where this flcid is employed as 
an instrument of culture, the crops obtained owe part of their nitrogen 
to the quantity of this compound which has been applied to the grow- 
ing plants. The same inference may fairly be drawn in regard to the 
effect of nitric acid — when, in the form of nitrates, it exists or is pro- 
duced naturally in the soil. 

4°. That other compound bodies, such as are contained in urine, or are 
produced during the decay of animal matter, may also enter into the 
circulation of plants, and yield nitrogen to promote their growth. 

On the whole, however, there seem strong reasons for believing that 
plants are mainly dependent on ammonia and nitric acid for the nitro- 
gen they contain ; and that they obtain it most readily, and with least 
labour, so to speak, from these compounds, — though nature* has kindly 
fitted them for deriving a stinted supply from other sources, when these 
substances are not present in sufficient abundance. 

How far each of these compounds is employed by nature, as an in- 
strument in promoting the general vegetation of the globe, will be con- 
sidered in a subsequent lecture. 

• Liebi^ and others say that plants arc incapable of appropriating or assimilating the nitro- 
gen which enters into their circulation in the simple state. We shall consider this ques- 
tion hereafter. 



LECTURE V. 

How does the food enter into the circulation of plants — Structure of the several parts of 
plants — Functions of the root — Course of the sap — Cause of its ascent — Functions of 
the stem— of the leaves— and of the bark — Circumstances by which the exercise of these 
functions is modified. 

Having now taken a general view of the source from which plants 
derive the elementary substances of which their solid parts consist, and of 
the states of combination in which these elements enter into the vegeta- 
ble circulation, — the next step in our inquiry is — how are these substan- 
ces admitted into the interior of living plants — and under what condi-' 
tions or regulations? "We are thus led to study the structure and func- 
tions of the several parts of plants, and the circumstances by which the 
exercise of these functions is observed to be modified. 

§ 1. General structure of plants ^ and of their several parts. 

Plants consist essentially of three parts — the roots, the stem, and the 
leaves. The former spread themselves in various directions through 
the soil, as the latter do through the air, and the stem is dependent for its 
food and increase on the rapidity with which the roots shoot out and ex- 
tend, and on the number and luxuriance of the leaves. 

We shall obtain a clearer idea of the relative structure of these several 
parts by first directing our attention to that of the stem. 

The stem consists apparently of four parts — the pith, the wood, the 
bark, and the medullary rays. The pith and the medullary rays, how- 
ever, are similarly constituted, and are only prolongations of one and 
the same substance. The pith forms a solid cylinder of soft and spongy 
matter, which ascends through the central part of the stem, and varies 
in thickness with the species and with the age of the trunk or branch. 
The wood surrounds the pith in the form of a hollow cylinder, and is itself 
covered by another hollow cylinder of bark. In trees or branches of 
considerable age the wood consists of two parts, the oldest or heart wood^ 
often of a brownish colour, and the newer external wood or alburnum, 
which is generally softer and less dense than the heart wood. The bark 
also is easily separated into two portions, the inner bark or liber, and 
the epidermis or outer covering of the tree. The pith and the bark are 
connected together by thin vertical columns or partitions, which inter- 
sect the wood and divide it into triangular segments. A cross section 
of the trunk or branch of a tree exhibits these thin columns extending 
in the form of rays, or like the spokes of a wheel, from the centre to 
the circumference. Though they form in reality thin and continuous 
vertical plates, yet from the appearance they present in the cross sec- 
lion of a piece of wood, they are distinguished by the name of medulla- 
ry rays. 

These several parts of the stem are composed of bundles of small 
tubes or hollow cylindrical vessels of various sizes, and of different 
kinds, the structure of which it is unnecessary for us to study. They 



76 STRUCTURE OF THE STEMS, ROOTS, AND LEAVES OF PLANTS. 

are all intended to contain liquid and gaseous substances, and to convey 
them in a vertical, and sometimes in a horizontal, direction. The 
tubes which compose the wood and bark are arranged vertically, as may 
readily be seen on examining a piece of wood even with the naked eye, 
and are intended to convey the sap upwards to the leaves and down- 
wards to the roots. Those of which the pith and medullary plates con- 
sist are arranged horizontally, and appear to be intended to maintain a 
lateral intercourse between the pith and the bark — perhaps even to place 
the heart of the tree within the influence of the external air. 

The root, though prior in its origin to the stem, may nevertheless for 
the purpose of illustration be considered as its downward and lateral 
prolongation into the earth — as the branches are its upward prolonga- 
tion into the air.* When they leave the lower part of the trunk of the 
tree, they differ little in their internal structure from the stem itself. 
As they taper off', however, first the heart wood, then the pith, gradual- 
ly disappear, till, towards their extremities, tliey consist only of a soft 
central woody part and its covering of soft bark. These are connected 
with, or are respectively prolongations of, the new wood and bark of the 
trunk and branches. At the extreme points of the roots the bark be- 
comes white, soft, spongy, and full of pores and vessels. It is by these 
spongy extremities only, or chiefly, that liquid and gaseous substances 
are capable either of entering into, or of making their escape from, the 
interior of the root. 

The branches and twigs are extensions of the trunk; and of the 
former, the leaves may be considered as a still further extension. The 
fibres of the leaf are minute ramifications of the woody matter of the 
twigs, are connected through them with the wood of the branches and 
stems, and from this wood receive the sap which they contain. The 
green part of the leaf may be considered as a special expansion of the 
bark, by which it is fitted to act upon the air, in the same way as the 
spongy mass into which the bark is changed at the extremity of the root, 
is fitted to act upon the water and other substances it meets with in the 
soil. For as the fibres of the leaf are connected with the wood of the 
stem, so the green part of the leaf is connected with its bark, and from 
this green part the sap first begins to descend towards the root. 

§2. The functions of the root. 

The position in whichthe roots of plants in their natural state are ge- 
nerally placed, has hitherto prevented their functions from being so ac- 
curately investigated as those of the leaves and of the stem. While, 
therefore, the main purposes they are intended to serve are universally 

* The correctness of this comparison is prove<I by the fact that, in many trees, the branch 
if planted will become a root, and Ihe root, if exposed to the air, will gradually be trans- 
formeii into a branch. The banana in the forest, and Ibe oirrant tree in our gardens, are 
familiar instances of trees spontaneously plantina their branches, and causing them to per- 
form the functions of roots. In like manner, " if the stem of a young plum or cherry-tree, 
or of a willow, be bent in the autumn so that one-half of the top can be laid in the earth and 
one-half of the root be at the same lime taken carefully up — sheltered at first and after- 
wards gradually exposed to the cold — and if in the following year the remaining part of the 
top and root be treated in the same way. the branches of the top will become roots, and the 
ramifications of the roots will become branches, producing leaves, flowers, and fruit in due 
season. — [Lnwlon's Encyclo^^adia of Ag^riculture.] The tree is thus reversed in position, 
and the roots and branches being thus mutually convertible cannot be materially unlike in 
general structure. 



II 



ROOTS ABSORB AQUEOUS SOLUTIONS, AND O^XTGEN. 77 

Known and understood, the precise way in which these ends are accom- 
plished by the roots, and the powers with which they are invested, are 
still to a considerable degree matters of dispute. 

I. It appears certain that they are possessed of the power of absorb- 
ing water in large quantity from the soil, and of transmitting it upwards 
to the stem. The amount of water thus absorbed depends greatly upon 
the nature of the soil and of the climate in which a plant grows, but 
much also upon the specific structure of its leaves and the extent of its 
foliage. 

II. The analogy of the leaves and young twigs would lead us to 
suppose that, when in a proper state of moisture, the roots should 
also be capable of absorbing gaseous substances from the air which 
pervades the soil. Experiment, however, has not yet shown this to be 
the case. 

We know, however, that they are capable of absorbing gases through 
the medium of water. For if the roots of a plant are placed in water 
containing carbonic acid in the state of solution, this gas is found gradu- 
ally to disappear. It is extracted from the water by the roots. And if 
the water in which the roots are immersed be contained in a bottle only 
partially filled with the liquid, while the remainder is occupied by at- 
mospheric air, the oxygen in this air will also slowly diminish. It will 
be absorbed by the roots through the medium of the water.* 

Again, if in the place of the atmospheric air in this bottle, carbonic 
acid be substituted, the plant will droop and in a few days will die. The 
same will take place, if instead of common air or carbonic acid, nitro- 
gen or hydrogen gases be introduced into the bottle. The plant will not 
live when its roots are exposed to the sole action of any of the three. 

It is obvious, therefore, that the roots of plants absorb gaseous sub- 
stances from the air which surrounds their roots, at least indirectly and 
through the medium of water. It appears also that from this air they 
have the power of selecting a certain portion of oxygen when this gas is 
present in it. Thirdly, that though they can absorb carbonic acid to a 
limited amount without injury to the plant, yet that a copious supply of 
this gas, unmixed with oxygen, is fatal to vegetable life. This deduction 
is confirmed by the fact that, in localities where carbonic acid ascends 
through fissures in the subjacent rocks and saturates the soil, the growth 
of grass is found to be very much retarded. And, lastly, since nitrogen 
is believed not to be in itself noxious to vegetable life, the death of the 
plant in water surrounded by this gas, is supposed to imply that the pre- 
sence of oxygen is necessary about the roots of a growing and healthy 
plant, and that one of the s{)ecial functions of the roots is constantly to 
absorb this oxygen. 

This supposition is in accordance with the fact that, in the dark, the 
leaves of plants absorb oxygen from the atmosphere; for we have al- 
ready seen reason to expect that, from their analogous structure, the roots 
and leaves in similar circumstances should perform also analogous func- 
tions. At the same time, if the roots do require the access and presence 

* It will be recollected that water absorbs about 4 per cent, of its bulk of air from the at- 
mosphere, of which about one-third is oxygen. If the roots extract this oxygen from the 
water, the latter will agaiq drink in a fresh portion from the atmospheric air which floats 
above it. 



78 DO SOLID SUBSTANCES ENTER THE ROOTS? 

of oxygen in the soil, it would further appear that those of some plants! | 
require it more than those of others ; inasmuch as some genera, like the 
grasses, love an open and friable soil, into which the air is more com- 
pletely excluded. — [Sprengel, Chemie, II., p. 337.] 

III. We have in a former lecture (IV. p. 64) concluded from facts 
there stated, that solid substances, which are soluble in water, accom- 
pany this liquid when it enters into the circulation of the plant. This 
appears to be true both of organic and inorganic substances. Potash, 
soda, lime, and magnesia thus find their way into the interior of plants, 
as well as those substances of animal and vegetable origin to which the 
observations made in the fourth lecture were intended more especially to 
apply. Even silica,* considered to be almost insoluble in water, enters 
by the roots, and is found in some cases in considerable quantities in the 
stem. Some persons have hence been led to conclude that solid sub- 
stances, undissolved, if in a minute state of division, may be drawn into 
the pores of the root and may then be carried by the sap upwards to the 
stem. 

Considered as a mere question of vegetable mechanics, argued as such 
among physiologists, it is of little moment whether we adopt or reject 
this opinion. One physiologist may state that the pores by which the 
food enters into the roots are so minute as to baffle the powers of the best 
constructed microscope, and, therefore, that to no particles of solid mat- 
ter can they by possibility give admission — while another may believe 
solid matter to be capable of a mechanical division so minute as to jiass 
through the pores of the finest membrane. As to the mere fact itself, it 
matters not which is right, or which of the two we follow. The adoption 
of the latter opinion implies in itself nrerely that foreign substances, 
unnecessary, perhaps injurious to vegetable life, may be carried forward 
by the flowing juices until in some still part of the current, or in some 
narrower vessel, they are arrested and there permanently lodged in the 
solid substance of the plant. 

By inference, however, the adoption of this opinion implies also, that 
the inorganic substances found in plants, — those which remain in the 
form of ash when the plant is burned, — are accidental or)\y , not essential 
to its constitution. For since they may have been introduced in a mere 
state of minute mechanical division suspended in the sap, they ought to 
consist of such substances chiefly as the soil contains in the greatest 
abundance, and they ought to vary in kind and relative quantity with 
every variation in the soil. In a clay land the ash should consist chiefly 
of alumina, f in a sandy soil chiefly of silica. But if, as chemical in- 
quiry appears to indicate, the nature of the ash is not accidental, but es- 
sential, and in some degree constant, even in very different soils, this 
latter inference is inadmissible; — and in reasoning backwards from this 
fact, we find ourselves constrained to reject the opinion that substances 
are capable of entering into the roots of plants in a solid state — and this 
without reference at all to the mechanical question, as to the relative size 
of the pores of the spongy roots or of the particles into which solid mat- 
ter may be divided. 

* Silica i« the name given by chemists to the pure matter of flint or of rock crystal. Sand 
and sandstones consist almost entirely of n Uca. 
t Alumina is the pure eailh of clay. 



SELECTING POWER OF THE ROOTS. "T9 

IV. We are thus brought to the consideration of the alleged selecting 
power of the roots, which, if rightly atrributed to them, must be con- 
sidered as one of the most important functions of which they are pos- 
sessed. It is a function, however, the existence of which is disputed by 
many eminent physiologists. But as the adojnion or rejection of it will 
materially influence our reasonings, as well as our theoretical views, in 
regard to some of the most vital processes of vegetation, — it will be pro- 
per to weigh carefully the evidence on which this power is assigned to 
the roots of plants. 

1°. The leaves, as we shall hereafter see, possess in a high degree 
the power of selecting from the atmosphere one or more gaseous sub- 
stances, leaving the nitrogen, chiefly, unchanged in bulk. The absorp- 
tion of carbonic acid and the diminution of the oxygen in the experi- 
ments above described, appear to be analogous effiscts, and would seem 
to imply in the roots the existence of a similar power. 

2°. Dr. Daubeny found that pelargoniums, barley {hordeum vulgare)^ 
and the winged pea {lolus tetragonolobus)^ though made to grow in a 
soil containing much strontia,* appeared to absorb none of this earth, for 
none was found in the ash left by the stem and roots of the plant when 
burned. In like manner De Saussure observed that polygonum persi- 
caria refused to absorb acetate of lime from the soil, though it freely took 
up common salt.r— [Lindley's Theory of Horticulture, p. 19.] 

3°. Plants of different species, growing in the same soil, leave, when 
burned, an ash which in ev£ry case contains either different substances, 
or the same substances in unlike proportions. Thus if a bean and a 
grain of wheat be grown side by side, the stem of the plant from the lat- 
ter seed will be found to contain silica, from the former none.f 

4°. But the same plant grown in soils unlike in character and com- 
position, contains always — if they are present in the soil at all — very 
nearly the same kindj of earthy matters in nearly the same proportion. 
Thus the stalks of corn plants, of the grasses, of the bamboo, and of many 
others, always contain silica, in whatever soil they grow, or at least are 
capable of growing with any degree of luxuriance. 

With the view of testing this point, Lampadius prepared five square 
patches of ground, manured them with equal quantities of a mixture of 
horse and cow dung, sowed them with equal measures of the same 
"wlieat, and on four of these patches strewed respectively five pounds of 
finely powdered quartz (siliceous safld), of chalk, of alumina, and of 
carbonate of magnesia, and left one undressed. The produce of seed 
from each, in the above order, weighed 24i, 28|, 26i, 21i, and 20 ounces 
respectively. The grain, chaff", and straw, from each of the patches 
left nearly the same quantity of ash — the weights varying only from 3-7 
to 4-08 per cent., and the roots and chaff" being richest in inorganic mat- 
ter. The relative proportions of silica, alumina, lime, and magnesia, 

* Watered with a solution of nitrate of strontia. Strontia is an earthy substance resem- 
bling lime, which is found in certain rocks and mineral veins, bui which has not hitherto been 
observed in the ashes of plants. 

t It is not strictly correct that the bean will absorb no silica, but the quantity it will take up 
will be only one-thirteenth of that taken up by the wheat plant— the per centage of silica in 
the ash of bean straw being, according to Sprengei, only 022, while in wheat straw ifis 2 87 
per cent. Pea straw contains four times as much as that of the bean, or 996 per cent. 

J For more precise information on this point, see the subsequent lectures, " Onihe inor- 
ganic constituents of plants," (Part II.) 



80 PLANTS MAY ABSORB POISONOUS SUBSTANCES. 

were the same in all. — [Meyen Jahreshericht, 1839, p. 1.] Provided, 
therefore, the substances which plants prefer be present in the soil, the 
kind of inorg:anic matter they take up, or of ash they leave, is not mate- 
rially affected by the presence of other substances, even in somewhat 
larger quantity. 

These facts all point to the same conclusion, that the roots have the 
power of selecting fronl the soil in which fhey grow, those substances 
which are best fitted to promote the growth or to maintain the healthy 
condition of the plants they are destined to feed. 

5°. It has been stated above that the roots of certain plants refuse to 
absorb nitrate of sfrontia and acetate of lime, though presented to them 
in a state of solution — the same is true of certain coloured solutions which 
have been found incapable of finding their way into the circulation of 
plants whose roots have been immersed in them. On the other hand, 
it is a matter of frequent observation that the roots absorb solutions con- 
taining substances which speedily cause the death of the plant. Arsenic, 
opium, salts of iron, of lead, and of copper, and many other substances, 
are capable of being absorbed in quantities which prove injurious to the 
living vegetable — and on this ground chiefly many physiologists refuse to 
acknowledge that the roots of plants are by nature endowed with any 
definite and constant power of selection at all. But this argument is of 
equal force against the possession of such a power by animals or even by 
man himself; since, with our more perfect discriminating powers, aided 
by our reason too, we every day swallow with our food what is more or 
less injurious, and occasionally even fatal, to human life.* 

On the whole, therefore, it appears niost reasonable to conclude that 
the roots are so constituted as (1°) to be able generally to select from the 
soil, in preference, those substances which are most suitable to the nature 
of the plant — (2°) where these are not to be met with, to admit certain 
others in their steadf — (3°) to refuse admission also to certain substan- 
ces likely to injure the plant, though unable to discriminate and reject 
every thing hurtful or unbeneficial which may be presented to them in • 
a state of solution. 

The object of nature, indeed, seems to be to guard the plant against 
the more common and usual dangers only — not against such as rarely 
present themselves in the situations in which it is destined to grow, or 
against substances which are unlikely even to demand admissi.on into its 
roots. How -useless a waste of skill, if I may so speak, would it have 
been to endow the roots of each plant with the power of distinguishing 
and rejecting opium and arsenic and the thousand other poisonous sub- 
stances which the physiologist can present to them, but which in a state 
of nature — on its natural soil and in its natural climate — the living vege- 
table is never destined to encounter ! 

* I may here remark (hat it is by no means an extraordinary power which these circum- 
stances seem to show the roots of plants to possess. h\ the presence of oxygen, nitrogen, 
and carbonic add, in equal quantities, water will prefer and will select ihe latter. From a 
mixture of lime and magnesia, acetic or sulphuric acid will select and separate Ihe former. 
Is it unrearonable to suppose the roolsof plants— the organs ofalivin?beinff — to he endowed 
with powers of discrimination at least as preat as those possessed by dead matterl 

t This conclusion is not strictly contained in the premises above stated, but the facts from 
which it is drawn will be fully explained in treating of the inorganic constituents of plants. 
It is liitroc^uced here for the purpose of giving a complete view of what appears to be the 
true powers of diacriaiinalion possessed by the root. 



EXCRETORY POWER OF THE ROOTS. 81 

V. Another function of tlie roots of plants^ in regard to which physiol- 
ogists are divided in opinion at the present day, is what is called their 
excretory power. 

1°. When barley or other grain is caused to germinate in pure chalk, 
acetate of lime* is uniformly found to be mixed with it after the germi- 
nation is somewhat advanced (Becquerel and Mateucci, Ann. deChem. 
et de Phys., 1 v., p. 310.) In this case the acetic acid must have been given 
off (excreted) by the young roots during the germination of the seed. 

This fact may be considered as the foundation of the excretory theory 
as it is called. This theory, supported by the high authority of Decan- 
doUe, and illustrated by the apparently convincing experiments of Ma- 
caire, {Ann. de Chim. el de Phys., lii., p. 225,) has more recently been met 
by counter-experiments of Braconnot, (Ixxii. p. 27,) and is now in a great 
measure rejected by many eminent vegetable physiologists. It may in- 
deed be considered as quite certain that the ai)plicaiion of this theory by 
Decandolle and others to the explanation of the benefits arising from a 
rotation of crops, is not confirmed, or j^ roved to be correct, by any exper- 
iments on the subject that have hitherto been pul)lished.f 

According to Decandolle, plants, like animals, have the jwwer of se- 
lecting from their food, as it passes through their vascular system, such 
portions as are likely to nourish them, and of rejecting, by their roots, 

* Acetate of lime is a combination of acetic acid or vinegar with lime derived from the chalk. 

■f The discordant results of Macaire and Braconnot were as follow : 

1° Macaire observed that wlien plants of ClwndriUa Muralis were grown in rain water 
they imparted to it something of the saiell and taste of opium. Braconnot confirmed this, 
bin attributed it to wounds in the roots which allowed the proper juice of the plant to escape.' 
He says it is almost impossible to free the young roots from the soil in which they have grown, 
without injuring them and causing the sap to exude. 

2°. Euphorbia Peplus (Petty Spurge) imparted to the water in which it grew a gummi- 
resinous substance of a very acrid taste. In the hands of Braconnot it yielded to the water 
scarcely any organic matter, and that only slightly bitterish. 

3°. Braconnot washed the soil in which plants of Eu.p/ioi-bia Breuni and Asclepias Incur- 
nala were growing in pots, and obtained a solution containing earthy and alkaline salts with 
only a trace of organic matter. 

He also washed the soil in which the Pi^ppy (Papaver Somni/erum) had been grown ten 
years successively. The soluiion, besides inorganic earthy and alkaline salts, gave a consid- 
erable quantity of acetic acid (in the form of acetate of lime) and a trace of brown organic 
matter. He infers that these several plants do not excrete any organic matter in sufficient 
quantity to be injuiious to themselves. 

iP. Macaire observed that when separate portions of the roots of the same plant of Mercu- 
ria'.is Annua were immersed in separate vessels, the one containing pure water and the 
other a solution of acetate of lead, — the solution of lead was absorbed by the plant, — was to 
be traced in every part of it, and afterwards was partially transmitted to the pure water. Bra- 
connot observed the same results, but he found the entrance of the lead into the second vessel 
to be owing to the ascent of the fluid up the outer surface ofthe one root and down the exterior 
of the other, and tliat, by preventing the possibility of this passage, no lead could be detected 
among the pure water. 

Tlie conclusion^ of Macah'e, therefore, in favour of the rotation theory of Decandolle 
must be considered as at present inadmissible, and we shall hereafter see reason to coin- 
cide, at least to a certain extent, in the conclusion of Braconnot, "that if these excretions 
(of organic matter) really take place in the natural state ofthe plant, they are as yet so ob 
Bcure and so little known as to justify the presumption that some other explanation must 
be given of the general system of rotation." Various illustrations have been given by differ- 
ent observers of this supposed excreting power ofthe roots. Among the most recent are 
those of Nietner, wtio ascribes the luxuriant rye crops obtained without manure after three 
years of clover, to the excretions of this plant in the soil, which, like those ofthe pea and 
Dean to the wheat, he supposes 'o be nourishing food to the i-ye. He also states that the 
beet or the turnip after tobacco has an unpleasant taste, and is scarcely eatable, which he 
altribntes to the excretions ofthe tobacco plant. Meyen ascribes the effect of the clover to 
the green manure supplied by its roots and stubble and Uiat ofthe tobacco to the undecom- 
posed organic substances contained in the sap and substance ofthe roots and stems of this 
plant, of which so large a quantity is left behind in tlie field. — [^ley en' s Jahresbericht, 1839, 
p. 5.]— These objections of Meyen are not without their weight, but we shall hereafter eee 
ihitt they embody only half the truth. 



82 EXPERIlvrENTS OF DE SAUSSURE. 

when the sap descends, such as are unfit to contribute to their support, 
or would be hurtful to them if not rejected from their system. He further 
supposes that, after a time, the soil in which a certain kind of plant 
grows becomes so loaded with this rejected matter, that the same plant 
refuses any longer to flourish in it. And, thirdly, that though injurious 
to the plant from which it has been derived, this rejected matter may be 
wholesome food to plants of a different order, and hence the advantage to 
be derived from a rotation of crops. 

There seems no good reason to doubt that the roots of plants do at 
times — it may be constantly — reject organic substances from their roots. 
The acetic acid given off during germination, and the same acid found 
by Braconnot in remarkable quantity in the soil in which the poppy 
{papaver somniferum) has grown — may be regarded as sufficient evi- 
dence of the fact — but the quantity of such organic matter hitherto de- 
tected among what may be safely viewed as the real excretions of plants, 
seems by far too small to account for the remarkable natural results at- 
tendant upon a rotation of crops. 

The consideration of these results, as well as of the general theory of 
such a rotation, will form a distinct topic of consideration in a subsequent 
part of these lectures. I shall, therefore, only mention one or two facts 
which seem to me capable of explanation only on the supposition that 
the roots of ])lants are endowed wiih the power of rejecting, and that 
they do constantly reject, when the sap returns from the leaf, some of 
the substances which they had previously taken up from the soil. 

1°. De Saussure made numerous experiments on the quantity of ash 
pe cent, left by the same plant at different periods of its growth. Among 
other results obtained by him, it appeared — 

A. That the quantity of incombustible or inorganic matter in the dif- 
ferent parts of the plant was different at different periods of (he year. 
Thus the dry leaves of the horse chestnut, gathered in May, left 7-2 per 
cent., towards the end of July 8-4 per cent., and in the end of Septem- 
ber 8-6 per cent, of ash; the dry leaves of the hazel in June left 6-2, 
and in September 7 per cent. ; and those of the poplar {populus nigra) 
in May 6-6, and in September 9-3 per cent, of ash. These results are 
easily explained on the supposition that the roots continued to absorb 
and send up to the leaves during the whole summer the saline and 
earthy substances of which the ash consisted. But — 

B. He observed also that the quantity of the inorganic substances in 
— or the ash left by — the entire plant, diminished as it approached to 
maturity. Thus the dry plants of the vetch, of the golden rod {solida- 
go vulgaris), of the turnsol {helianthus annuus), and of wheat, left res- 
pectively of ash, at three different periods of their growth, [Davy's 
Agricultural Chemistry, Lecture 111,] — 

Before flowering. In flower Seeds ripp. 

per cent. per cent. per cent. 

Vetch 15 12-2 6-6 

Golden rod . . . 9-2 5-7 5-0 

Turnsol .... 14-7 13-7 9-3 

Wheat .... 7-9 5-4 3-3 

This diminution in the proportion of ash, might arise either from an 

increase in the absolute quantity of vegetable matter in the plants ac- 



PROPORTION or SILICA IN THE ASH OF PLANTS. 83 

companying their increase in size — or from a portion of the saline and 

earthy matters they contained heing again rejected by the roots. But 

if the former be the true explanation, the relative proportions of the 

several substances of which the ash itself consisted, in the several cases, 

should have been the same at the several periods when the experiments 

were made. But this was by no means the ease. Thus, to refer only 

to the quantity of silica contained in the ash left by each of the above 

plants at the several stages of their growth, the ashes of the 

Before flowering. In flower. Seeds ripe. 

peT cent. per cent. per cent. 

Vetch contained ... 1*5 1*5 1*75 

Golden rod 1-5 1-5 3-5 

Turnsol 1-5 1-5 3-75 

Wheat ...... 12-5 26-0 51-0 

If, then, the proportion of silica in the ash increased in some cases 
four-fold, while the whole quantity of ash left by the plant decreased, it 
appears evident that some part of that which existed in the plant during 
the earlier periods of its growth must have been excreted or rejected by 
the roots, as it advanced towards maturity. 

2°. This conclusion is confirmed and carried farther by another con- 
sideration. The quantity of ash left by the ripe wheat plant, in the 
above experiments of De Saussure, amounted to 3-3 per cent. ; — of 
which ash, 51 percent., or rather more than one-half, was silica. This 
silica, it is believed, could oi]ly have entered into tlie circulation of the 
plant in a state of solution in water, and could only be dissolved by the 
agency of potash or soda. But, according to Sprengel, the potash, soda» 
and silica, are to each other in the grain and straw of wheat, in the pro- 
portions of — 

Potash. Soda. Silica. 

Grain .... 0-225 0-24 0-4 

Straw .... 0-20 0-29 2-87 

Or, supposing the grain to equal one-half the weight of the straw— 

their relative proportions in the whole plant will be nearly as 21 potash, 

27 soda, 205 silica, or the weight of the silica is upwards of four times 

the weights of the potash and soda taken together. 

Now silica requires nearly half its weight of potash to render it solu- 
ble in water,* or three-fifths of its weight of a mixture of nearly equal 
parts of potash and soda. The quantity of these alkaline substances 
found in the plant, therefore, is b}^ no means suflticient to have dissolved 
and brought into its circulation the whole of the silica it contains. One 
of two things, therefore, must have taken place. Either a portion of 
the potash and soda present in the plant in the earlier stages of its 
growth must have escaped from its roots at a later stage, f leaving the 
silica behind it — or the same quantity of alkali must have circulated 
through the plant several limes — bringing in its burden of silica, deposit- 

* A soluble glass may be made by melting together in a crucible for six hours 10 parts of 
carbonate of potash, 15 of silica, and 1 of charcoal powder. 

t De Saussure does not state the exact relative quantities of potash and soda at the several 
periods of tiie growth of wheat, though they appear to have gradually diminished. It 
seems, indeed, to be true of many plants, that the potash and soda they contain diminishes 
in quantity as their age increases. Thus the weight of potash in the juice of the ripe or 
eweet grape, is said to be less than in the unripe or sour grape — and the leaves of the potato 
^ave been found more rich in potash before than after blossoming (Liebig). 



64 CAN THE ROOTS MODIFY THE FOOD OF PLANTS? 

ing it in the vascular system of the plant, and again returning to the 
soil for a fresh supply. In either case the roots must have allowed it 
egress as well as ingress. But the fact, that the proportion of silica in 
the plant goes on increasing as it continues to grow, is in favour of the 
latter view — and renders it very probable ihat the same quantity of al- 
kali returns again and again into the circulation, bringing with it sup- 
plies of silica and probably of other substances which the plant requires 
from the soil. And while this view appears to be the more probable, it 
also presents an interesting illustration of what may probably be the 
kind of function discharged by the potash and other inorganic substances 
found in the substance of plants — a question we shall hereafter have oc- 
casion to consider at some length. 

The above considerations, therefore, to which I might add others of a 
similar kind, satisfy me that the roots of plants do possess the power of 
excreting various substances which are held in solution by the sap on its 
return from the stem — and which having performed their functions in 
the interior of the plant are no longer fitted, in their existing condition, 
to minister to its sustenance or growth. Nor is it likely that this excre- 
tory power is restricted solely to the emission of inorganic substances. 
Other soluble matters of organic origin are, no doubt, permitted to es- 
cape into the soil — though whether of such a kind as must necessarily 
be injurious to the plant from which they have been extruded, or to such 
a degree as alo7ie to render a rotation of crops necessary, neither reason- 
ing nor experiment has hitherto satisfactorily shown. 

VI. The roots have the power of absorbing, and in some measure of 
selecting, food from the soil — can they also modify or alter it as it passes 
through them ? A colourless sap is observed to ascend through the 
roots. From the very extremity up to the foot of the stem a cross sec- 
tion exhibits little trace of colouring matter, even when the soil contains 
animal and vegetable substances which are soluble, and which give dark 
coloured solutions, [such as the liquid manure of the fold-yard.] Does 
such matter never enter the root ? If it does, it must be speedily changed 
or transformed into new compounds. 

We have as yet too few experiinents upon this subject to enable us to 
decide with any degree of certainty in regard to this function of the root. 

It is probable, however, that as the sap passes through the plant, it is 
constantly, though gradually, undergoing a series of changes, from the 
lime when it first enters the root till it again reaches it on its return from 
the leaf 

Can we conceive the existence of any powers in the root, or in the 
whole plant, of a still more refined kind? The germinating seed gives 
off acetic acid into the soil, — does this acetic acid dissolve lime from the 
soil and return with it again, as some suppose (Liebig), into the circula- 
tion of ihe plant?* Is acetic acid produced and excreted by the seed 
for this very refined purpose? We have concluded that in the wheat 
plant the potash and soda probably go and come several times during its 
growth, and the ripening of its seed. Is this a contrivance of nature to 

* Braconnot found acetate of lime in very small quantities to be singularly hurtful to vege- 
tation, and acetate of magnesia a little less so. He only mentions, however, some experi- 
ments upon mercurialis annua, [Ann. de Chim. et de Phys. Ixxii. p. 36,] and as Saussura 
found that some plants actually refused to talie it up at all, these acetates may not be equally 
injurious to all plants. 



THE SAP ASCENDS THROUGH THE WOOD. 85 

make up for the scarcity of alkaline substances in the soil — or would the 
same mode of operation be employed if potash and soda were present 
in greater abundance ? Or where the alkalies are present in greater 
abundance, might not more work be done by them in the same 
time, — might not the plant be built up the faster and the larger, when 
there were more hands, so to speak, to do the work ? Is the action of 
inorganic substances upon vegetation to be explained by the existence 
of a jjower resident in the roots or other parts of plants, by which such 
operations as this are directed or superintended ? There are many 
mysteries connected with the nature and phenomena of vegetable life, 
which we have been unable as yet to induce nature to reveal to us.* 
But the morning light is already kindling on tlie tops of the mountains, 
and we may hope that the deepest vallies will not forever remain obscure. 

§ 3. The course of the sap. 

If the trunk of a tree be cut off above the roots, and the lower extrem- 
ity be immediately plunged into a solution of madder or other colouring 
substances, the coloured liquid will ascend and will gradually tinge the 
wood. This ascent will continue till the colour can also be observed 
in the nerves of the leaf. If at this stage in the experiment the trunk 
be cut across at various heights, the wood alone will appear coloured, 
the bark remaining entirely untinged. But if the process be allowed 
still to continue when the coloured matter has reached the leaf, and after 
some further time the stem be cut across, the bark also will appear dyed, 
and the tinge will be perceptible further and further from the leaf the 
longer the experiment is carried on, till at length both bark and wood 
will be coloured to the very bottom of the stem. 

Or if the root of a living plant, as in the experiment of Macaire de- 
tailed in a preceding note, be immersed in a metallic solution — such 
as a solution of acetate of lead, — which it is capable of absorbing with- 
out immediate injury, and different portions of the plant be examined 
after the lapse of different periods of titne, — first the stem, afterwards 
the leaves, then the bark of the upper part of the stem, and lastly that 
of the lower part of the stem, will exhibit traces of lead. 

These experiments show that the sap which enters by the roots as- 
cends through the vessels of the wood, diffuses itself over the surface 
of leaves, and then descends by the bark to the extremities of the root. 

But what becomes of the sap when it reaches the root? Is it deliver- 
ed into the soil, or does it recommence the same course, and again, re- 
])eatedly perhaps, circulate through the stem, leaves, and bark ? This 
question has been partly answered by what has been stated in the pre- 
ceding section. When the sap reaches the extremity of the root, it ap- 
pears to give off to the soil both solid and fluid substances of a kind and 

• The roots of trees will travel to comparatively great distances, and in various directions, 
in search of water: the roots of sainfoin {Esparsetle) will penetrate 10 or 12 feet through the 
calcareous rubbly subsoil, or down the fissures of limestone rocks on which they delight to 
grow. Is this the result of some perceptive power in the plant — or is it merely by accident 
that the roots display these tendencies'? 

Those who are in any degree acquainted with the speculations of the German physiolo- 
gists of the greatest name — in regard to the soul and even the immorlality of plants — will not 
accuse me of going very far in alluding to the possible existence of some such perceptive 
power in plants. . Von Martins gets rid of objectors by speaking of them as '■'■ scientific men 
to whom the power of comprehending the transcendental has been imparled in a lower degree." 
See Mey en' sJahresbeiicht, 1S39, or i^illiman's Journal for January, 1841, p. 170. 



■g6 CAPILLARY ATTRACTIOX. 

to an amount which probably differ with every species of plant. The 
remainder of the sap and of the substances it holds in solution must be 
diffused through the cellular spongy terminations of the roots, and, with 
the new supply of liquid imbibed from the soil, returned again to the 
stem with the ascending current. 

But what causes the sap thus to ascend and descend ? By what 
power is it first sucked up through the roots, and afterwards forced down 
again from the leaves? Several answers have been given to this ques- 
tion. 

1°. When the end of a wide tube, either of metal or of glass, is 
plunged into water, the liquid will rise within the tube sensibly to the 
same level as that at which it stands in the vessel. But if a capillary* 
tube be employed instead of one with a wide bore, the liquid will rise, 
and will permanently remain at a considerably higher level within than 
without the tube. The cause of this rise has been ascribed to an attrac- 
tion which the sides of the tube have for the liquid, and which is suffi- 
ciently strong to raise it and to keep it up above the proper level of the 
water. The force itself is generally distinguished by the name o^ capil- 
lary attraction. 

Now, the wood of a tree, as we have seen, is composed of a mass of 
fine tubes, and through these the sap has been said to rise by capillary 
attraction. But if the top of a vine be cut off when it is juicy and full 
of sap, the liquid will exude from the newly formed surface, and if the 
air be excluded, will flow for a length of lime, and may be collected in 
a considerable quantity [Lindley's Theory of Horticulture, p. 47, note]. 
Such a flow of the sap is not to be accounted for by mere capillary at- 
traction — the sides of tubes cannot draw up a fluid beyond their own 
extremities. 

2°. To supply the defect of this hypothesis, De Saussure supposed 
that the fluid at first introduced by capillary attraction into the extremi- 
ties of the root, was afterwards propelled upwards by the alternate con- 
traction and expansion of the lubes of which the wood of the root and 
stem is composed. This alternate contraction and expansion he also 
supposed to be caused by a peculiar irritating property of the sap itself, 
which caused each successive part of the tube into which it found ad- 
mission to contract for the purpose of expelling it. Mr. Knight also as- 
cribed the ascent of the sap to a similar contraction of certain other parts 
of the stem. Being once raised, he supposed it to return again or de- 
scend b}'' its own weight — but in drooping branches it is obvious that the 
sap must be actually driven or drawn upwards from the leaves on its re- 
turn to the root. These explanations, therefore, are still unsatisfactory. 

3^. If one end of an open glass tube be covered with a piece of mois- 
tened bladder or other fine animal membrane, tied tightly over it, and a 
strong solution of sugar in water be then poured into the open end of the 
tube, so as to cover the membrane to the depth of several inches, and if 
the closed end be then introduced to the depth of an inch below the sur- 
face of a vessel of pure water, the water will after a short time pass 
through the bladder inwards, and the column of liquid in the tube will 
increase in height. This ascent will continue, till in favourable circum- 

Glass tubes perforated by a very fine bore, like a human hair, are called capillary tnbea. 
Such are those of which thermometers are usually made. 



CAUSE OF THE ASCENT OF THE SAP. 87 

Stances the fluid will reach the height of several feet, and will flow out 
or run over at the open end of the tube. At the same lime the water in 
the vessel will become sweet, indicating that while so much liijuid has 
passed through the membrane inwards, a quantity has also passed out- 
wards, carrying sugar along with it.* To these opposite eflects DutrO' 
chet, who first drew attention to the fact, gave the names of Endosmose, 
denoting the inward progress, and Exosmose, the outward progress of the 
fluid. He supposed them to he due to the action of two opposite cur- 
rents of electricity, and he likens the {)henomena observed during the 
circulation of the sap in plants, to the appearances presented during the 
above experiment. 

Without discussing the degree of probabiUty which exists as to the in- 
fluence of electricity in producing the phenomena of endosmose and ex- 
osmose, it must be admitted that the appearances themselves bear a 
strong resemblance to those presented in the absorption and excretion of 
fluids by the roots of plants — and point very distinctly to at least a 
kindred cause. 

Thus, if the spongy termination of the root represent the thin porous 
membrane in the above experiment — the sap with which the tubes of 
the wood are filled, the artificial solution introduced into the experimen- 
tal tube — and the water in the soil, the water or aqueous solution into 
which the closed extremity of the tube is introduced, — we have a series 
of conditions precisely similar to those in the experiment. Fluids ought 
consequently to enter from the soil into the roots, and thence to ascend 
into the stem, as in nature they appear to do. 

This ascent, we have said, will continue till the fluid in the tubes of 
the wood (the sap) is reduced to a density as low as that of the liquid 
entering the roots from the soil. But in a growing tree, clothed with 
foliage, this will never happen. The leaves are continually exhaling 
aqueous vapour, as one of their constant functions, and sometimes in 
very large quantity. The sap, therefore, when it reaches the leaves, is 
concentrated or thickened, and rendered more dense by the separation 
of the water, so that when it descends to the root, and again begins its 
upward course, it will admit of large dilution before its density can be 
so far diminished as to approach that of the comparatively pure water 
which is absorbed from the soil. And this illustration of the ascent of 
the sap apy)ears the more correct from the obvious purpose it points out 
— (in addition to others long recognised) — as served by the evaporation 
which is constantly taking place from the surface of the leaf. 

Still the cause of the ascent of the sap is not the more clear that we 
can imitate it in some measure by an artificial experiment. But it will 
be conceded by the strictest reasoners on physical phenomena, that to 
have obtained the command, or even a partial control, over a natural 

* Instead of sugar, common salt, gum, or other soluble substances may be dissolved in 
the water introduced at first into the tube, and the denser this solution the larger the quantity 
of water which will enter by the membrane, and the greater the height to which the column 
will rise. It ceases in all cases to rise only when the portions of liquid within and without 
the membrane attain nearly to the same density [i. e. contain nearly the same weight of solid 
matter in solution.] Instead of pure water the vessel into which the extremity of the tube 
is plunged may also contain a weak-solution of some soluble substance — such as lime or soda 
— in which case, while the sugar, or salt, or gum, will pass outwards, in smaller quantity, the 
lime or soda will pass inwards, aJong with the currents of water In which they are severally 
dissolved. 



88 DECOMPOSITION TAKES PLACE IN THE STEM. 

power, is a considerable step towards a clear conception of the nature of 
that power itself. If the f)henomena of endosraose can hereafter be 
clearly and indubitably traced to the as;ency of electricity we shall have 
advanced still another step, and shall be enabled to devise other means 
by which a more perfect imitation of nature may be effected, or a more 
complete control asserted over the phenomena of vegetable circulation. 

§ 4. Functions of the stem. 

The functions of the stem are probably as various as those of the 
root, though the circumstances under which they are performed neces- 
sarily involve these functions in considerable obscurity. 

The pith which forms the central part of the stem consists, as I have 
already stated, of tubes disposed horizontally. When a coloured fluid 
is permitted to enter the lower part of the stem in the experiments 
above described, the pith remains untinctured in the centre of the col- 
oured wood. It does not, therefore, serve for the conveyance of the sap. 
Nor does it seem to be vitally necessary to the health and growth of the 
plant, since Mr. Knight has shown that, from the interior of many trees, 
it may be removed without apparent injury, and in nature, as trees ad- 
vance in age, it gradually diminishes in bulk, and in some species be- 
comes apparently obliterated. 

The vessels of the wood, which surrounds the pith, perform proba- 
bly both a mechanical and a chemical function. They serve to convey 
upwards to the leaf the various substances which enter by the roots. 
This is their mechanical function. But during its progress upwards, 
the sap appears to undergo a series of changes. When it reaches the 
leaves it is no longer in the slate in which it ascended from the root inio 
the stem. The difficulty of extracting the sap from the wood, at dif- 
ferent heights, has prevented very rigorous experiments from being 
made on its nature and contents at the several stages of its ascent. 
These it is obvious inust vary with the species and age of the plant, and 
■with the season of the j'ear ai which the experiment is made. But the 
general result to be drawn from such observations as have hitherto been 
made, is, that those substances which enter directly into the root, when 
mingled with such as have already passed through the circulation of the 
plant, undergo, during their ascent, a gradual preparation for that state 
in which they become fit to minister to the growth of the plant. This 
preparation is completed in a great measure in the leaf, though further 
changes still go on as the sap descends through the bark. This deduc- 
tion is strengthened by the fact that gaseous substances of various kinds 
and in varying quantities exist in the interior of the wood of the grow- 
ing plant. These gaseous subtances, according to Boucherie, are in 
some cases equal in bulk to one-twentieth part of the entire trunk of the 
tree in which they exist. They probably move upwards along with 
the sap, and are more or less completely discharged into the atmosphere 
through the pores of the leaves. That these gaseous substances not 
only differ in quantity, but in kind also, with the age and species of 
the tree, and with the season of ihe year, may, I think, be considered 
as almost amounting to a proof that they have not been inhaled direct- 
ly by the roots, but are the result of chemical decompositions which 



FUNCTIONS OF THE STF.M AND LEAVES. 89 

have taken place on the stem Itself, as the sap mounted upwards to- 
wards the leaves. 

We have seen that the roots exercise a kind of discriminating power 
in admitting to the circulaiion of the plant the various substances which 
are present in the soil. The vessels of the stem exhibit an analogous 
power of admitting or rejecting the solutions of different substances into 
which they may be immersed. Thus Boucherie states that, when the 
trunks of several trees of the same species are cut off" above the roots, 
and the lower extremities immediately plunged into solutions of differ- 
ent substances, some of these solutions will quickly ascend into and pen- 
etrate the entire substance of the tree immersed in them, while others 
will not be admitted at all, or with extreme slowness only, by the ves- 
sels of the stems to which they are respectively presented. On the 
other hand, that which is rejected by one species will be readily admit- 
ted by another. Whether this partial stoppage of, or total refusal to ad-- 
JDit, certain substances, be a mere contractile effort on the part of the 
vessels, or be the result of a chemical change by which their exclusion 
is effected or resisted, does not as yet clearly appear. That it does not 
depend upon the lightness and porosity of the wood, as might be sup- 
posed, is shown by the observation that the poplar is less easily pene- 
trated in this way than the beech, and the willow than the pear tree, 
the maple, or the plane. 

These various functions of the woody part of the stem are performed 
chiefly by the newer wood or alburnum, or, as it is often called, the sap 
wood of the tree. As the heart wood becomes older, the tubes of which 
it consists are either gradually stopped up by the deposition of solid 
substances which have entered by the roots, or by the formation of 
chemical compounds, which, like concretions in the bodies of animals, 
slowly increase in size till the vessels become entirely closed — or they 
are by degrees compressed laterally by the growth of wood around them, 
so as to become incapable of transmitting the ascending fluids. Per- 
haps the result is in most cases due in part to both these causes. This 
more or less perfect stoppage of the oldest vessels is one reason why the 
course of the sap is chiefly directed through the newer tubes.* 

The functions of the bark, which forms the exterior portion of the 
stem, will be more advantageously described, after we shall have con- 
sidered the purposes served by the leaves. 

§ 5. Functions of the leaves. 

The vessels of which the sap wood is composed extend upwards into 
the fibres of the leaf. Through these vessels the sap ascends, and from 
their extremities diffuses itself over the surface of the leaf. Here it un- 
dergoes important chemical changes, the extent, if not the exact nature, 
of which v/ill a[>pear from a short description of the functions which the 
leaves are known or are believed to discharge. 

1°. When the roots of a living plant are immersed in water, it is a 

* As the newest roots are prolongations of the newest wood, it may be supposed that the 
fact of these roots being the chief absorbents from the soil, Is a sufficient reason why that 
which is absorbed by them should also pass up through the wood with which they are most 
closely connected. But that the pores of the heart wood are really incapable of transmit- 
ting fluids, is shown by plunging the newly cut stem of a tree into a coloured solution — the 
newer wood will be dyed, while more or less of the central portion will remain unchanged. 



90 ESCAPE OF WATERY VAPOUR FROM THE LEAVES. 

matter of familiar observation that the water gradually diminishes in 
bulk, and will at length entirely disappear, even when evaporation into 
the air is entirely prevented. The water which thus disappears is taken 
up by the roots of the plant, is carried up to the leaves, is there spread 
out over a large surface exposed to the sun and to the air, and in the 
form of vapour escapes in considerable proportion through the pores of 
the leaves and diffuses itself through the atmosphere. 

The quantity of water which thus escapes from the surface of the 
leaves varies with the moisture of the soil, with the species of plant, 
with the temperature and moisture of the air, and with the season of the 
year. According to the experiments of Hales, it is also dependent on 
the presence of the sun, and is scarcely perceptible during the night. 
He found that a sun-flower, 3^ feet high, lost from its leaves during 12 
hours of one day 30, and of another day 20 ounces of water, while during 
a warm night, without dew, it lost only three ounces, and in a dewy 
night underwent no diminution in weight.* 

This loss of watery vapour by the leaf is ascribed to two different 
kinds of action. First, to a natural perspiration from the pores of the 
leaf, similar to the insensible perspiration which is continually proceed- 
ing from the skins of healthy animals ;" and second, to a mechanical 
evaporation like that which gradually takes place from the surface of 
moist bodies when exposed to hot or dry air. The relative amount of 
loss due to each of these two modes of action respectively, must differ 
very much in different species of plants, being dependent in a great 
measure on the special structure of the leaf. In all cases, however, the 
natural perspiration is believed very greatly to exceed the mere mechan- 
ical evaporation — though the results of Hales, and of other experimen- 
ters, show that both processes proceed with the greatest rapidity under the 
influence of a warm dry atmosphere, aided by the direct rays of the sun. 

Among the several purposes served by this escape of watery vapour 
from the surface of the leaf, it is of importance for us to notice the direct 

' When the escape of vapour from the leaves is more rapid than the supply of water from 
the roots, the leaves droop, dry, and wither. Sucli is sometimes the case with growing 
crops in very hot weather, and it always happens when a twig or flower is plucked and sep- 
arated from the stem or root. When thus separated the leaves still continue to give off wa- 
tery vapour into the air, and consequently the sap ascends from the twig or stalk to supply 
the place of the water thus exhaled. 

But as the sap ascends it must leave the vessels empty of fluid, and air must rush in ta 
fill the empty space. This will continue till nearly all the fluid has risen from the stem into 
the leaf, and the vessels of the wood are full of air. But if the stem of the twig or flower be 
placed in water this liquid will rise into it, air will be excluded, and the freshness and bloom 
of the leaves and flowers will be longer preserved. If the water into which they are intro- 
duced contain any substances in solution, these will I'ise along with the water, and will grad- 
ually make their way through all the vessels of the wood, till they can be detected in the 
leaves. By this means even large trees may in a short time be saturated with saline solu- 
tions, capable of preserving them from decay. It is only necessary to cut down or saw 
through the tree and insert its lower extremity into the prepared solution, when the action 
of the sun and air upon the leaves will cause it spontaneously to ascend. Thus corrosive 
sublimate (the subject of Kyan's Patent) may be injected with ease, or pyroUgnite ofiron^ 
(iron dissolved in wood vinegar,) which Boucherie recommends as equally efficient and 
much more economical, {Ann. de Chiin. et de Phys. Ix-xiv. p. 113.] The process is finished 
when the liquid is found to have risen to the leaf. Coloured solutions may in the same way 
be injected and the wood tinged to any required shade. One of the chief benefits attendant 
upon the catting of wood in the winter, appears to be that tlie absence of leaves prevents the 
exhaustion of the sap and the ascent of air into the vessels of the wood — the oxygen of this 
air tending to induce decay. But the sap may be retained, and the air excluded almost as 
effectually, at any other season of the year, by stripping the tree of its leaves and branches a 
few days before it is cut dowa. 



I 



OTHER VOLATILE SUBSTANCES EXHALED. 91 

chemical influence it exercises over the growth of the plant. As the water 
disappears from the leaf, the roots must absorb from the soil at least an 
equal supply. This water brings with it the soluble substances, organ- 
ic and inorganic, which the soil contains, and thus in proportion to the 
activity with which the leaves lose their watery vapour, will be the 
quantity of those substances which enter from the soil into the general 
circulation of the plant. This enables us to understand how substances, 
very sparingly soluble in water, should yet be foimd in the interior of 
plants, and in very considerable quantity, at almost every stage of their 
growth. 

2°. Besides watery vapour, however, the leaves of nearly all plants 
exhale at the same lime other volatile compounds in greater or less 
abundance. In the petals of flowers, we are familiar with such exha- 
lations — often of an agreeable and odoriferous character. In the case of 
plants and trees also wliich emit a sensible odour, we readily recognise 
the fact of volatile substances being given off by the leaves. But even 
when the sense of smell gives us no indication of tlieir emission from a 
single leaf or a single plant, the introduction of a number of such in- 
odorous plants into the confined atmosphere of a small room after a time 
satisfies us that even they part with some volatile matter from their 
leaves, which makes itself perceptible to our imperfect organs only when 
in a concentrated state. The probability therefore is, that the leaves of 
all plants emit, along with the watery vapour which they evolve, cer- 
tain other volatile substances also, though often in quantities so minute 
as to escape detection by our unaided senses. By the emission of these 
substances the plant probably relieves itself of what would prove inju- 
rious if retained, though of the chemical nature and composition of these 
exhalations little or nothing has yet been ascertained. 

3°. If the branch of a living plant be so bent that some of its leaves 
can be introduced beneath the edge of an inverted tumbler full of water, 
and if the leaves be then exposed to the rays of the sun, bubbles o-f gas 
will be seen to form on the leaf, and gradually to rise through the Vv'ater 
and collect in the bottom of the tumbler. If this gas be examined it 
will be found to be pure oxygen. 

If the water contain carbonic acid gas, or if during the experiment a 
little carbonic acid be introduced, this gas will be found gradually to dis- 
appear, while the oxygen will continue to accumulate. 

Or if the experiment be made by introducing a living plant into a large 
bell-glass full of common atmospheric air, allowing it to grow there for 
12 hours in the sunshine, and then examining or arialysing the air con- 
|:ained in the glass, the result will be of a precisely similar kind. The 
per centage of oxygen in the air will have increased.* And if the ex- 
periment be varied by the introduction of a small quantity of carbonic 
acid gas into the jar, this gas will be found as before to diminish in quan- 
tity, while the oxygen increases. The conclusion drawn from these 
experiments, therefore, is, that the leaves of plants, when exfoud to the 
rays of the sun, absorb carbonic acid from tlie air and give off pure oxy- 
gen gas. 

It has been already staled that the proportion of carbonic acid present 

• It will be remembered that atmospheric air contains about 21 per cent, of oxygen gas. 



92 OXYGEN IS EMITTED DURING THE DAY, 

in the atmosphere is exceedingly snnall, [ahout l-2500lh of this bulk — 
see Lecture II., p. 30;] but if for the purpose of experiment we increase 
this proportion in a gallon of air to five or ten per cent., introduce a liv- 
ing plant into it, and expose it to the sunshine, the carbonic acid will 
gradually disappear as before, while the oxygen will increase. And if 
we analyse the air and estimate the exact bulk of each of these gases 
present in it at the close of our experiment, we shall find that the oxygen 
has increased generally by as much as the carbonic acid has diminished. 
That is to say, if five cubic inches of the latter have disappeared, five 
cubic inches will have been added to the bulk of the oxygen. The 
above general conclusion, therefore, is rendered more precise by this ex- 
periment, which appears to show that under the injiuence of the sun's 
rays the leaves ofjjtants absorb carbonic acid from the air, and at the same 
time give ojf \^ equal bulk of oxygen gas. 

And as carbonic acid (COo) contains its own bulk of oxygen gas* 
combined with a certain known weight of carbon, it is fiirther inferred 
that the oxygen given off by the leaves is the same whicli has been pre- 
viously absorbed in the form of carbonic acid, and therefore it is usually 
stated as a function of the leaves — that in the sunshine they absorb car- 
bonic add from the air, decompose it in the interior of the leaf retainits 
carbon, and again reject or emit the oxygen it contained. 

This conclusion presents a very simple view of the relations of oxygen 
and carbonic acid respectively to the living leaf in the presence of the 
sun, and it appears to be fairly deduced from the facts above stated. 
It has occasionally been observed, however, that the bulk of oxygen 
given off by the leaf has not been precisely equal to tliat of the carbonic 
acid absorbed, [see Persoz, Chimie Moleculaire, p. 54,] and hence it is 
also fairly concluded that a portion of the oxygen of the carbonic acid 
which enters the leaf is retained, and made available in the production 
of the various substances which are formed in the vascular system of 
different plants. On the other hand it is stated by Sprengel, that if com- 
pounds containing much oxygen be presented to the roots of plants, and 
thus introduced into the circulation, they are also decomposed, and the 
oxygen they contain in part or in whole given off by the leaves, so that, 
under certain circumstances, the bulk of the oxygen which escapes is 
actually greater than that of the carbonic acid which is absorbed by the 
leaves. Such is the case, for example, when the roots are moistened 
with water containing carbonic, sulphuric, or nitric acids. — [Sprengel 
Chemie, II., p. 344.] 

It is of importance to note these deviations from apparent simplicity 
in the relative bulks of the two gases which are respectively given off 
and absorbed by all living vegetables. There are numerous cases of the 
formation of substances in the interior of plants which theory would fail 
to account for with any degree of ease, were these apparent anomalies 
to be neglected. This will more distinctly appear when in a subsequent 
lecture we shall inquire hoio or by what chemical changes the substan- 
ces which plants contain, or of which they consist, are produced from 
the food which they draw from the air and from the soil. 

This the reader will recollecf is proved by burning charcoal in a bottle of oxygen gas till 
combustion ceases, when nearly the whole of the oxygen is converted into carbonic acid, but 
without change of bulk.— See Lecture III., p. 45. 



AN1> CARBOISIC ACID DURING THE NIGHT. 93 

The most general and probable expression, therefore, for the function 
of the leaf, now under consideration, appears lo be that in the sunshine 
the leaves absorb from the air caibonic acid, and at the same time 
evolve oxygen gas, ihe bulk of the latter gas given off being nearly 
equal to that of the former which is taken in — the relative bulks of the 
two gases varying more or less with the species of plant, as well as 
with the circumstances under which it is caused or is fitted to grow.* 

4°. Such is the relation of the leaf to the oxygen and carbonic acid 
of the atmosphere in the presence of the sun. During the night their 
action is reversed, they emit carbonic acid and absorb oxygen. This is 
proved by experiments similar to those above described. For if the 
plant which has remained under the bell-glass for 12 hours in the sun- 
shine — during which time the oxygen has sensibly increased, and the 
carbonic acid diminislied in bulk — be allowed to remain in the same air 
through the fullowing night, the oxygen will be found to have decreased, 
while the carbonic acid will be present in larger quantity than in the 
evening of the previous day. 

The carbonic acid thus given off during the night is supposed to be 
partly derived from the soil through the roots, and partly from the sub- 
stance of the plant itself. The oxygen absorbed either combines with 
the carbon of the plant to form a portion of the carbonic acid which is 
at the same time given off or is employed in producing some of the 
other oxidixed [containing oxygen in considerable quantity] compounds 
that exist in the sap. 

As a general rule, the quantity of carbonic acid given off during the 
night is far from being equal to that which is absorbed during the day. 
Still it is obvious that a plant loses carbon precisely in proportion to the 
amount of this gas given off. Hence, when the days are longest, the 
plant will lose the least, and where the sun is brightest it v/ill gain the 
fastest; since other things being equal, the decomposition of carbonic 
acid proceeds most rapidly where the sky is the clearest, and the rays 
of the sun most powerful.. Hence we see why in Northern regions, 
where spring, summer, and autumn are all comprised in one long day 
— vegetation should proceed with such rapidity. The decomposition of 
the carbonic acid goes on without intermission, the leaves have no night 
of rest, but nature has kindly provided that, where the season of 
warmth is so fleeting, there should be no cessation to the necessary 
growth of food for man and beast. 

This comparison of the functions performed by the leaf, during the 
day and night respectively, explains the chemical nature of the blanching 
of vegetables practised by the gardener, as well as the cause of the pale 
colour of plants that grow naturally in the absence of light. 

When exj)osed to the sun, the leaves of these sickly vegetables evolve 
oxygen, and gradually become green and healthy. Woody matter is 
formed, and the stems become strong and fibrous. 

The light of the sun, in the existing economy of nature, is indeed 
equally necessary to the health of plants and of animals. The former 

* As the oxygen given off by the leaves is always the result of a chemical decomposition, 
by which the carbonic acid or other compound is deprived of a portion, at least, of its oxy- 
gen or rfe-oxidized, this function of the leaves in the presence of the sun is often spoken of 
as their deoxidizing power. 



94 LEAVES SOaiETIMES EMIT CHLORINE. 

become pale and sickly, and refuse to perform their most important 
chemical functions when excluded from the light. The bloom disap- 
pears from the human cheek, the body wastes away, and the spirit 
sinks, when the unhappy prisoner is debarred from the sight of the blessed 
sun. In his system, too, the presence of light is necessary to the perfor- 
mance of those chemical functions on which the healthy condition of the 
vital fluids depends. 

The processes by which oxygen and carbonic acid are respectively 
evolved in plants have been likened by physiologists to the respiration 
and digestion of animals. It is supposed that when plants respire they 
give off carbonic acid as animals do, and that when they digest they 
evolve oxygen. Respiration also, it is said, proceeds at all times, diges- 
tion only in the light of the sun. Though these views are confessedly 
conjectural, they are founded upon striking analogies, and may reason- 
ably be entertained as matters of opinion. 

6°. Other species of decomposition also, besides that o{ c/e- oxidization^ 
go on in the leaf, or are there made manifest. Thus when plants grow 
in a soil containing much common salt (chloride of sodium) or other 
chlorides, they have been observed by Sprengel and Mej'en to evolve 
chloride* gas from their leaves. This takes place, however, more dur- 
ing the night than during the day. Some plants also give off ammonia, 
(Lecture IV., p. 70,) while others (cruciferas), according to Dr. Daube- 
ny, [in his Three Lectures on Agriculture, p. 69,] emit from their leaves 
pure nitrogen gas. 

The evolution of chlorine implies the previous decomposition of the 
chlorides, which have been absorbed from the soil; while that of nitro- 
gen may be due to the decomposition of ammonia, of nitric acid, or 
of some other compound containing nitrogen, which has entered into the 
circulation by the roots. The exact mode and nature of the decompo- 
sition of these substances, and the purposes served by them in the vegeta- 
ble economy, will come under our consideration in a subsetjuent lecture. 

The leaf has been described (p. 76) as an expansion of the bark. 
It consists internally of two layers of veins or vascular fibres laid one 
over the other, the upper connected with the wood — the lower with the 
inner bark. It is covered on both sides by a thin membrane (epider- 
mis), the expansion of the outer bark. This thin menibane is studded 
with numerous small pores or mouths (stomata), which vary in size and 
in number with the nature of the plant, and with the circumstances in 
which it is intended to grow. It is from the pores in the upper part of 
.the leaf that substances are supposed to be exhaled, while every thing 
that is inhaled enters by those which are observed in the under side of 
the leaf.f This opinion, however, is not universally received, it being 
admitted by some that the power both of absorbing and of emitting 
may be possessed by the under surface of the leaf. 

7°. We have seen that the chief su])ply of the fluids which constitute 

* Chlorine is a gas of a greenish yelli^w colour, having an unpleasant taste and a suffocating 
odour. When it combines with other substances it forms chlorides. It exists in, and im- 
parts its smell to, "chloride of lime, which is employed for disinfecting purposes, and it 
forms upwards of half the weight of common salt. 

t This is illustrated by the action of a cabbage leaf on a wound. If the upper side be ap- 
plied, the sore is protected and quickly heals, while the under side draws it and produces a 
constant discharge. 



FUNCTIONS OF THE FLOWER-LEAVES. 95 

the sap of plants, is derived from the soil. The under side of the 
leaves of plants is also supposed by some to be capable of absorbing 
moisture from the air, either in the form of watery vapour, or when it 
falls upon the leaves in the state of dew. Like the roots also they may 
absorb with the dew any substances the latter happens to hold in solu- 
tion. A,nd thus plants may, in soine degree, be nourished by The vola- 
tile organic substances which ascend from the earth duiing the heat of 
the day, and which are again in a great measure precipitated with the 
evening dew. 

Whether the leaves ever absorb nitrogen gas from the air has not as 
yet been determined with sufficient accuracy. If they do, it must in gene- 
ral be in very small quantity only, since it has hitherto escaped detec- 
tion. In like manner it is doubtful how far ihey regularly absorb any 
other substances which the air is supposed to contain. Thus it is known 
that nitric acid exists in the air in very minute quantity. Some chem- 
ists also believe that ammonia is extensively diffused through the atmos- 
phere in an exceedingly diluted state. Do the leaves of plants absorb 
these substances? Is the absorption of them one of the constant and ne- 
cessary functions of the leaves ? The reply to these (juestions must be 
very uncertain, and any principle which professes to be based upon such 
a reply must be regarded only as a matter of opinion. 

8°. The petals of flower-leaves perform a somewhat different function 
from those of the ordinary leaves of a plant. They absorb oxygen at 
all times — though more by day than by night — and they constantly emit 
carbonic acid. The bulk of the latter gas evolved, however, is less than 
that of the oxygen taken in. The absorption of oxygen gas, and the 
constant production of carbonic acid, is, in some flowers, so great as to 
cause a perceptible increase of temperature — and to this slow combus- 
tion, so to speak, the proper heat observed in the flowers of many plants 
has been attributed. 

According to some authors, the flower-leaves also emit pure nitrogen 
gas. — [Sprengel, Chemie, II., p. 347.] This fact has not yet been deter- 
mined by a sufficient number of accurate experiments; it is in accord- 
ance, however, with the results of Boussingault, that, when a plant 
flowers and approaches to maturity, the nitrogen it contains becomes 
less. If confirmed, this evolution of nitrogen would throw an interest- 
ing light on the most advantageous employment of green crops, both for 
the purposes of manure and for the feeding of cattle. 

9°. When the leaves of a plant begin to decay, either naturally as in 
autumn, or from artificial or accidental causes, they no longer absorb 
and decompose carbonic acid, even under the influence of the sun's rays. 
On the contrary, they absorb oxygen, like the petals of the flower, new 
compounds are formed within their substance — their green colour disap- 
pears — they become yellow — they wither, die, and drop from the tree — 
their final function, as the organs of a Hving being, is discharged. They 
then undergo new changes, are subjected to a new series of influences, 
and are made to serve new purposes in the economy of nature. These 
we shall hereafter find to be no less interesting and important in refer- 
ence to a further end, than are the functions of the living leaf to the 
growth and nourishment of the plant. — [See subsequent lecture, " On the 
law of the decay of organic substances.^^] 



96 CHEMiCAL FL;>'CTI0.NS or THE BARK. 

§ 6. Functions of the hark. 

The inner bark being connected with the under layer of vessels in the 
leaf, receives from them the sap after it has been changed by the action 
of the air and light, and transmits it downwards to the root. 

The outer bark, especially in young twigs and in the stalks of the 
grasses, so closely resembles the leaves in its appearance, that we can 
have no difficulty in admitting that it must, not unfrequently, perform 
similar functions. In the Cactus, the Stapelia, and other plants which 
produce no true leaves, this outer bark seems to perform all the functions 
which in other vegetable tribes are specially assigned to the abundant 
foliage. During its descent through the inner bark, therefore, the sap 
must in very many cases undergo chemical changes, more or less analo- 
gous to those which usually take place in the leaf. 

It is by means of the inner bark that the stems of trees, such as 
our forest and fruit trees, are enlarged by the deposition of annual 
layers of new wood. The woody fibre is formed or prepared in 
the leaf, and as the sap descends it is deposited beneath the inner sur- 
face of the inner bark. It thus happens that, as the sap descends, it is 
gradually deprived of the substances it held in solution when it left the 
leaf, and in consequence it becomes difficult to say how much of the 
change, which the sap is found to have undergone when it reaches the 
root, is due to chemical transformations produced during its descent, and 
how much to the deposition of the woody fibre and other matters it has 
parted with by the way. 

Among other evidences of such changes really taking place during 
the descent of the sap, I may mention an observation of Meyen [Jahres- 
bericht, 1839, p. 27], made in the course of his experiments on the re- 
production of the bark of trees. In these experiments he enclosed the 
naked wood in strong glass tubes, and in three cases out of eight the 
tubes were burst and shattered in pieces. This could only have arisen 
from the disengagement of gaseous substances, the result of decomposi- 
tion. While, therefore, such gases as enter by the roots or are evolved 
in the vessels of the wood during the ascent of the sap, escape by the 
leaf along with those which are disengaged in the leaf itself, it is proba- 
ble that those which are produced as the result of changes in the bark, 
descend with the downward sap, and are discharged by the root.* 

In the bark of the root it is probable that still further changes take 
place — and of a kind which can only be efTected during the absence of 
light. This is rendered probable by the fact that the bark of the root 
frequently contains substances which are not to be met with in any 
other part of the plant. Thus from the bark of the fresh root of the ap- 
ple tree a substance named phloridzine, possessed of considerable medi- 
cal virtues, may be readily extracted, though it does not exist in the 
bark either of the stem or of the branches. 

In fine, as the food which is introduced into the stomachs of animals, 
undergoes continual and successive chemical changes during its pro- 
gress through the entire alimentary canal — so, numerous phenomena 
indicate that the sap of plants is also subjected to unceasing transforma- 

* Sprengel says ttiat the stems and twigs, and the stalks of the grasses, all absorb oxygen 
and give off carbonic acid. — Chemie. II., p. 341. 



KU-VCTIONS OF THE ROOT MODIFIED BY THE SOIL. 97 

lions, — in the root and in ihe stem as well as in the leaves, — at one time 
in the dark, at another under the influence of the sun's rays, — exposed 
when in the leaf to the full action of the air, — and when in the root al- 
most wholly secluded from its presence ; — the new compounds pro- 
duced in every instance being suited either to the nature of the plant or 
the wants and functions of that pari of it in which each transformation 
takes i)lace. 

To some of these transformations it will be necessary to advert more 
particularly, when we come to consider the special changes by which 
those substances of which plants chiefly consist, are formed out of these 
compounds on which they chiefly live. 

• § 7. Circumstances by which the functions of the various parts of plants 

are modified. 

Plants grow more or less luxuriantly, and their several parts are 
more or less largely developed, in obedience to numerous and varied 
circumstances. 

I. In regard to the special functions of the root, we have already seen 
that the access of atmospheric air is in some cases indispensable, while 
in others, by shooting vertically downwards, the roots appear to shun 
the approach of either air or light. It is obvious also that a certain de- 
gree of moisture in the soil, and a certain temperature, are necessary 
to the most healthy discharge of the functions of the root. In hot wea- 
ther the plant droops, because the roots do not absorb water from the 
soil with sufficient rapidity. And though it is probable that, at every 
temperature above that of absolute freezing, the food contained in the 
soil is absorbed and transmitted more or less slowly to the stem, yet it is 
well known that a genial warmth in the soil stimulates the roots to in- 
creased activity. The practice of gardeners in applying bottom heat in 
the artificial climate of the green-house and conservatory is founded on 
this well-known principle. 

But the nature of the soil in which plants grow has also much influ- 
ence on the way in which the functions of the root are discharged. As 
a general fact this also is well known, though the special qualities of the 
soil on which the greater or less activity of vegetation depends, are far 
from being generally understood. If the soil contain a sensible quantity 
of any substance which is noxious to plants, it is plain that their roots 
will be to a certain degree enfeebled, and their functions in consequence 
only imperfectly discharged. Or if the soil be deficient either in organic 
food, or in one or other of those inorganic substances which the plants 
necessarily require for the production of their several parts, the roots 
cannot perform their office with any degree of efficiency. Where the 
! necessary materials are wanting the builder must cease to work. So in 
a soil which contains no silica, the grain of wheat may germinate, but 
he stalk cannot be produced in a natural or healthy state, since silica is 
indispensable to its healthy construction. 

II. The ascent of the sap is modified chiefly by the season of the 
'■ year, by the heat of the day, and by the genus and age of the plant or 

tree. 

There seems reason to believe that the plant never sleeps, that even 
during the winter the circulation slowly proceeds, though the first 



98 ALSO THE RAPIDITY OF THE CIRCULATION. 

genial sunshine of the early spring stimulates it to increased activity. 
The o-eneral increased temperature of the air does not produce this ac- 
celeration in so remarkable a manner as the direct rays of the sun. The 
sap will flow and circulate on the side of a tree on which the sunshine 
falls, while it remains sensibly stagnant on the other. This is shown by 
the cutting down similar trees at more and more advanced periods of 
the spring, and immersing their lower extremities in coloured solutions. 
The wood and bark on one side of the tree will be coloured, w^hile, on 
the other, both will remain unstained. If a similar difference in the 
comparative rapidity of the circulation on opposite sides of a trunk or 
branch be supposed to prevail more or less throughout the year, we can 
readily account for the annual layers of wood being often thicker on 
the one half of the circumference of the stem than on the other. 

The sap is generally supposed to flow^ most rapidly during the spring, 
but if trees be cut down at different seasons, and immersed as above 
described, the coloured solution, according to Boucherie, reaches the 
leaves most rapidly in the autumn.* 

The heat of the day, other circumstances being the same, materially 
affects, for the time, the rapidity of the circulation. The more rapidly 
watery and other vapours are exhaled from the leaves, the more quick- 
ly must the sap flow upwards to supply the waste. If on two succes- 
sive days the loss by the leaves be, as in the experiment of Hales, above 
described, (p. 90,) as 2 to 3, the ascent of the sap must be accelerated 
or retarded in a similar proportion. Hence, every sensible variation in 
the temperature and moisture of the air, must also, to a certain extent, 
modify the flow of the sap ; must cause a greater or less transport of that 
food which the earth supplies, to be carried to every part of the plant, 
and must thus sensibly affect the luxuriance and growth of the whole. 

But the persistance of the leaves is a generic character, which has 
considerable influence upon the circulation in the evergreens. In the 
pine and the holly, from which the leaves do not fall in the autumn, the 
sap ascends and descends during all the colder months, — at a slower 
rate, it is true, than in the hot days of summer, yet much more sensibly 
than in the oak and ash, which spread their naked arms through the 
wintery air. This is illustrated by the experiments of Boucherie, who 
has observed that in December and January the entire wood of resinous 
trees may be readily and thoroughly penetrated by the spontaneous as- 
cent of saline and other solutions, into which their stems may be im- 
mersed. 

III. From what has just been stated, it will appear that the mechani- 
cal functions of the stem are subject to precisely the same influences as 
the ascent of the sap. As the tree advances in age, the vessels of the 
interior will become more or less obliterated, and the general course of 
the sap, will be gradually transferred to annual layers, more and more 

* Boucherie makes a distinction, not hitherto insisted upon hy physiologists, between the 
circulation on the surface of the tree by which the buds and young twigs are supported, and 
the interior circulation, which is not perfect until a latter period of the year. Hence in the 
spring, though the sap is flowing rapidly through the bark and the newest wood, coloured 
solutions will not penetrate the interior of the tree with any degree of rapidity. In autumn, 
on the other hand — when the fear of approaching winter has already descended upon the 
bark — the time of most active circulation has only arrived for the interior layers of the older 
wood. It is this season consequently that he finds most favourable for impregnating the 
trunks of trees with those solutions which are likely to preserve them from decay. — Ann, de 
Chim. et de Phys,, Ixxiv., p. 135. 



CHEMICAL RAYS IN THE SUN-BEAM. 99 

removed from the centre. It is this transference of the vital circula- 
tion to newer and more perfect vessels that enables the tree to grow and 
blossom and bear fruit through so long a life. In animals the vessels 
are gradually worn out by incessant action. None of them, through 
old age, are permitted to retire from the service of the body — and the 
whole system must stop when one of them is incapacitated for the 
further performance of its appointed duties. 

In regard to the chemical futictions of the stem, it is obvious that they 
are not assigned to the mere woody matter of the vessels and cells. 
They take place in these vessels, but the nature and extent of the chemi- 
cal changes themselves must be dependent upon the quantity and kinds 
of matter which ascend or descend in the sap. The entire chemical 
functions of the plant, therefore, must be dependent upon and must be 
modified by the nature of the substances which the soil and the air re- 
spectively present to the roots and to the leaves. 

IV. In describing the functions of the leaf, I have already had occa- 
sion to advert to the greater number of the circumstances by which the 
discharge of those functions is most materially atfected. We have seen 
that the purposes served by the leaf are entirely different according as 
the sun is above or below the horizon ; that the temperature and mois- 
ture of the air may indeed materially influence the rapidity with which 
its functions are discharged — but that the light of tlie sun actually deter- 
mines their nature. Thus the leaf becomes green and oxygen is given 
off in the presence of the sun, while in his absence carbonic acid is dis- 
engaged, and the whole plant is blanched. 

How necessary light is to the health of plants may be inferred from 
the eagerness with which they appear to long for it. How intensely 
does the sun-flower watch the daily course of the sun, — how do the 
countless blossoms nightly droop when he retires, — and the blanched 
plant strive to reach an open chink through which his light may reach 
it!* 

That the warmth of the sun has comparatively little to do with this 
specific action of his rays on the chemical functions of the leaf, is illus- 
trated by some interesting experiments of Mr. Hunt, on the effect of 
rays of light of different colours on the growing plant. He sowed cress 
seed, and exposed different portions of the soil in which the seeds were 
germinating, to the action of the red, yellow, green, and blue rays, 
which were transmitted by equal thicknesses of solutions of these seve- 
ral colours. " After ten days, there was under the blue fluid, a crop of 
cress of as bright a green as any which grew in full light and far more 
abundant. The crop was scanty under the green fluid, and of a pale 
yellow, unhealthy colour. Under the yellow solution, only two or three 
plants appeared, but less pale than those under the green, — while be- 
neath the red, a few more plants came up than under the yellow, though 
they also were of an unhealthy colour. The red and blue bottles being 
now mutually transferred, the crop formerly beneath the blue in a few 

' A potato has been observed to grow up in quest of light from the bottom of a well 
twelve feet deep— and in a dark cellar a shoot of 20 feet in length has been met with, the 
extremity of which had reached and rested at an open window. In the leaves of blanched 
vegetables peculiar chemical compounds are formed. Thus in the stalk of the potato a 
poisonous substance called solanin is produced, which disappears again when the stalk is ex- 
posed to the light and becomes green. 



100 FUKCTlOiVS or THE UUEEiN TWIGS. 



1 



days appeared blighted, while on the patch previously exposed to the 
red, some additional plants sprung up."* 

Besides the rays of heat and of light, the sun-beam contains what 
have been called chemical rays, not distinguishable by our senses, but 
capable of being recognized by the chemical etfects they produce. 
These rays appear to differ in kind, as the rays of different coloured 
light do. It is to the action of these chemical rays on the leaf, and 
especially to those which are associated with the blue light in the solar 
beam, that the chemical influence of the sun on the functions of the leaf 
is principally to be ascribed. 

It cannot be doubted that the warmth and moisture of a tropical cli- 
mate act as powerful stimulants — assistants it may be — to the leaf, in 
the absorption of carbonic acid from the air, and in that rapid appropria- 
tion (assimilation) of its carbon by which the growth of the plant is has- 
tened and promoted. But the bright sun, and especially the chemical in- 
fluence of his beams, must be regarded as the main agent in the wonderful 
development of a tropical vegetation. Under this influence the growth 
by the leaves at the expense of the air must be materially increased, 
and the plant be rendered less dependent upon the root and the soil for 
the food on which it lives. f 

V. The rapidity with which a plant grows has an important influence 
upon the share which the hark is permitted to take in the general 
nourishment of the whole. The green shoot performs in some degree 
the functions of the leaf. In vascular plants, therefore, which in a con- 
genial climate may almost be seen to grow, the entire rind of a tall tree 
may more or less effectually absorb carbonic acid from the atmosphere, 
during the presence of the sun. The broad leaves of the palm tree, 
when fully developed, render the plant in a great degree independent of 
the soil for organic food — and the large amount of absorbing surface in 
the long green tender stalks of the grasses, and of their tropical ana- 
logues, must materially contribute to the same end. Hence the pro- 
portion of organic matter derived from the air, in any crop we reap, 
must always be the greater the more rapid its general vegetation has 
been. 



It is a fact familiarly known to all of you, that, besides those circum- 
stances by which we can perceive the special functions of any one or- 
gan to be modified, there are many by which the entire economy of the 
plant is materially and simultaneously aftected. On this fact the prac- 
tice of agriculture is founded, and the various processes adopted by the 
practical farmer are only so many modes by which he hopes to influ- 

* London and Edinburgh Joicrnal of fScience, February, 1840. 

Might not our cheap blue glass be used with advantage in glazing hot-houses, conserva- 
tories, &c. 1 

t The effect of continued sunshine may be often seen in our corn-fields in May, when, 
under the influence of propitious weather, the young plants are shooting rapidly up. When 
such a field is bounded by a lofty hedge running nearly north and south, the ritges nearest 
the hedge on either side will be in the shade for nearly one-half of the day, and will invarin- 
bly.appearof a paler green and less healthy colour. If the hedge be studded with occasion; 1 
large'trees, the spots on which the shadows of those trees rest will be indicated by distinct 
pale green patches stretching further into the field than the first, and sometimes even thtn 
the second ridges. 



EFFECT OF MARLING. REWARDS OF NATURE. 101 

ence and promote the growth of tlie whole plant, and the discharge of 
the functions of all its parts. 

Though manures in the soil act immediately through the roots, they 
stimulate the growth of the entire plant; and though the application of 
a top-dressing may be supposed first to affect the leaf, yet the beneficial 
result of the experiment depends upon the influence which the dressing 
may exercise on every part of the vegetable tissue. 

In connection with this part of the subject, therefore, T sliall only 
further advert to a very remarkable fact mentioned by Sprengel, which 
seems, if correct, to be susceptible of important practical applications. 
He states that it has very frequently been observed in Holstein, that if, 
on an extent of level ground sown with corn, some fields be marled, and 
others left unmarled, the corn on the latter portions will grow less luxuri- 
antly and will yield a poorer crop than if the whole had been unmarled. 
Hence he adds, if the occupier of the unmarled field would not have a 
succession of poor crops, he must marl his land also.* 

Can it really be that nature thus rewards the diligent and the impro- 
ver? Do the plants which grow on a soil in higher condition take from 
the air more than their due share of the carbonic acid or other vegetable 
food it may contain, and leave to the tenants of the poorer soil a less pro- 
portion than they might otherwise draw from it ? How many interest- 
ing reflections does such a fact as this suggest ! What new views does 
it disclose of the fostering care of the great Contriver — of his kind encour- 
agement of every species of virtuous labour ! Can it fail to read to us a 
new and special lesson on the benefits to be derived from the application 
of skill and knowledge to the cultivation of the soil ? 

' Wenn namlich auf einer Feldflur Stiick um Sliick gemergelt worden ist, so wachsen 
die Friichte auf den nicht gemergelt en Feldern, auch wenn hier alia friiheren verhaltnisse 
ganz dic-selben bleiben, nicht inehr sogut, als ehedein ; wodurch die Besitzer jener Felder, 
wenn sie nicht fortwahrend geringe Erndten haben wollen, genothigt sind, gleichfails zu 
mergeln. Aus dieser liUchst vichtigen Ersctieinung, die man sehr hdufig in Holsteinschen 
bemerkt, &c. — Sprengel^Chemiefilr Landwirtfischa/t, I., p. 303. 



LECTURE VI. 

Substances of which plants chiefly consist— Woody fibre, Starch, Gum, Sugars— Their mu- 
tual relations and transformations — Gluten,Vegetable Albumen, Diastase — Acetic, Tartaric, 
Malic, Citric, and Oxalic Acids — General observations. 

From what has been stated regarding the structure of plants, it will be 
understood in what way the food is introduced into their circulation. The 
next inquiry appears to be how — by what chemical changes — is the food, 
when introduced, converted into those substances of which plants chiefly 
consist. But in order that we may clearly understand this point, it is 
necessary that we know first the nature and chemical constitution of the 
substances which are most largely formed from the food in the interior 
of the plant. To this point, therefore, I must previously direct your 
attention. 

If you were to collect all tlie varieties of plants which are within your 
reach — whether such as are cultivated and used for food — or such as 
grow more or less abundantly in a wild state — and were to extract their 
several juices, and to separate from each of these juices the chemical 
compounds it contains — you would gradually gather together so many 
different substances, all possessed of different properties, that you would 
scarcely be able to number them. 

But if at the same time you compared the weight of each substance 
thus collected with that of the entire plant from which it is derived, you 
would find also that the quantity of many of them is comparatively so 
minute that only a very small portion of the vital energies of the plant 
can be expended in producing them, — that they may be entirely neglect- 
ed in a general consideration of the great products of vegetation. Thus 
though quinine and morphine, the active ingredients in Peruvian bark 
and in opium, are most interesting substances, from their effect upon the 
human constitution, and their use in medicine, yet they form so small a 
fraction of the mass of the entire trees or plants from which they are ex- 
tracted, that it would be idle to attempt to convey to you any notion of 
the way in which plants grow and are fed, by showing you how such 
substances as these are produced from the food on which plants live. 

While, however, the examination would satisfy you that almost 
every species of plant produced in small quantity one or more sub- 
stances peculiar to itself, you would observe, at the same time, that 
every plant yielded a certain quantity of two or three substances com- 
mon to and produced by all, and in most cases constituting the greater 
portion of their bulk. Thus all trees and herbs produce wood or woody 
fibre, and of this substance you know that their chief bulk consists. 
Again, all the grains and roots you cultivate contain starch in large 
quantity, and the production of this starch is one of the great objects of 
the art of culture. The juices of trees, and of grasses, and of cultivated 
roots, contain sugar and gum, and sometimes in such quantity as to 
make their extraction a source of profit both to the grower and to the 



CONSTITUTION OF WOODY FIBRE. 103 

manufacturer. The flour of grain contains sugar also, and along with it 
two other substances, in small quantity, gluten and vegetable albumen^ 
which are of much importance in reference to the nutritive qualities of 
the different v.irietiesof flour. Sugar is also present in the juices of 
fruits, but it is there associated with various acid (sour) substances 
which disappear to a certain extent or change into sugar as the fruit 
ripens. 

Of these few substances the great bulk of vegetables of all kinds con- 
sists. They constitute nearly the whole mass of those various crops 
which the art of culture studies to raise for the use of man and beast. 
To the study of these substances, therefore, I shall at present confine 
your attention, and if I shall afterwards be able to make you under- 
stand how these few compound bodies are produced in the interior of a 
plant from the food it takes up, I shall succeed in conveying to you as 
much information in regard to this most interesting branch of our subject 
as will be necessary to a general explanation not only of the natural 
growth and increase of plants, but of the nature and efficacy of those 
artificial means which the practical farmer employs, in order to hasten 
their growth or enlarge their increase. 

§ 1. Woody fibre or lignin — its constitution and j^Toper ties. 

1°. When a portion of the stem of a herbaceous plant, or of the new- 
ly cut wood of the trunk or branch of a tree, is reduced to small pieces, 
and boiled in successive portions of water and alcohol, as long as any 
thing is taken up, a white fibrous inass remains, to which the name of 
woody fibre or lignin has been given. This substance has no taste or 
smell, and is perfectly insoluble in water. It is nearly identical in its 
chemical constitution and properties, whether it be obtained from the 
porous willow, or from the solid box tree, and the fibres of linen and of 
cotton consist essentially of the same substances. 

According to the analysis of Dr. Prout, this woody fibre when dried 

at 350° F., consists of 

From Box Wood. From the Willow. 

Carbon 50-0 49-8 

Hydrogen .... 5-55 5-58 

Oxygen .... 44*45 44*62 

100 100 

It will be recollected that water consists of oxygen and hydrogen, 
combined in the proportion, by weight, of 8 of the former to 1 of the lat- 
ter. (See Lecture II., p. 36.) Now if the hydrogen above given be 
multiplied by 8, the product will be found to be almost exactly the 
weight of the oxygen given — since 

5-55 X 8 = 44*40, and 
5-58 X 8 = 44*64. 
In woody fibre, therefore, the hydrogen and oxygen exist in the same 
proportion as in water, and its composition, therefore, might be repre- 
sented by 

Carbon 500 

Water 50*0 

100 



104 COMPOSITION OF WOOD. 

did we not know that woody fibre, when heated or distilled, cannot be 
resolved into carbon (charcoal) and water alone, and, therefore, cannot 
be supposed to consist of these alone. 

It is a remarkable character of this substance, however, that these two 
elements, hydrogen and oxygen, exist in it in the proportions to form 
M'ater, and we shall find the knowledge of this fact of great importance 
to us, when we come to inquire how this constituent of vegetables is 
formed — from the food on which they live. 

2°. If a portion of the wood of a tree be dried and analyzed without 

being previously digested in water, alcohol, and ether, as long as any 

thing is taken up, the proportion of the constituents is found to vary 

slightly with the species of tree, but in all cases the hydrogen is in larger 

quantity than is necessary to form water with the oxygen they Contain. 

Thus, according to Payen, the dry wood of the following trees consists of 

Ebony. Walnut. Oak. Beech. 

Carbon . . . 52-85 51-92 50-00 49-25 

Hydrogen . . 6-00 5 96 6-20 6-10 

Oxygen . . . 41-15 42-12 43-80 44-65 



100 100 100 100 

The carbon in these several kinds of wood differs as much as three 
per cent., but in each of them the product of the hydrogen, when multi- 
plied by 8, is considerably greater than the per centage of oxygen. 

3°. When the solid substance of wood is examined under the micro- 
scope it is observed to consist of two portions or kinds of matter, that of 
which the original sides of the cells and tubes is composed, called the 
cellular matter — the true woody fibre — and of a solid substance by which 
the cells are internally coated and strengthened, called the incrusting 
matter. It is in this latter substance that the excess of hydrogen, exhi- 
bited by the preceding analysis, is supposed to exist, the true woody 
fibre containing always the hydrogen and oxygen in the proportions ne- 
cessary to form water.* 

' Payen at first considered this incrusting matter as a peculiar substance, for which he 
proposed the nannie of scfero^ene. His first mode of separating it from the cellular matter 
was by treating the finely rasped wood (of the oak and beech) with nitric acid, which dis- 
solved out the incrusting matter and left the cellular matter behind. His second mode was 
to digest the wood with dilute sulphuric acid, by which the cellular matter was dissolved 
out, and the incrusting matter left. It is obvious, however, that no reliance whatever can be 
placed on the analyses of substances so treated, since they cannot fail to have undergone a 
chemical change by being exposed to the action of these strong acids. Further examination 
has satisfied Payen that the incrusting matter consists of at least three substances, of which 
one is soluble in water, alcohol, and ether, another in alcohol only, while the third is insolu. 
ble in any of these liquids. They are composed, according to his analyses, of 

Soluble in Soluble in 

Insoluble. alcohol only. water and alcohol. 

Carbon ... 48 628 6853 

Hydrogen .... 6 5 9 704 

Oxygen ... 46 313 24-43>' 



100 100 100 

It is impossible to say how far the substances analysed by Payen are to be considered as 
pure, or as actually existing in the pores, or in the incrusting matter of the woody fibre, but 
U is obvious that the presence of a variable quantity of such substances will necessarily 
cause that excess of hydrogen, in the entire wood, which appears in the analysis of the ebo- 
ny, walnut, oak, and beech woods, given in the text. That such an excess of hydrogen 
above what is necessary to form water with the oxygen, does exist in the wood of most trees 

[^ Meyen's Jahresberichf, 1839, p. 10.] 



COMPOSITION OF CELLULAR MATTER. 105 

It is exceedingly difficult in any case to separate the cellular from the 
incrusting matter of wood, so as to obtain the rr]eans of determining by 
analysis the exact difference in their elementary constitution. Under 
the impression that in very light and i)orous substances he should ob- 
tain the cellular matter in a purer form, Payen analysed the fibre of 
cotton — the pith of the elder, the cellular substance of the cucumber, of 
the mushroom, and of other fungi, the spongy matter which forms the 
extremities of the roots of plants, and various other similar substances, 
and in all these varieties he found the hydrogen and oxygen to exist in 
the proportions to form water. The mean of his analyses was very 
nearly as follows — which for the purpose of comparison I shall contrast 
with that of Dr. Prout : 

Woody fibre of box and Cellular matter of vascu- 

wlllow — Dr. Prout. lar plants — Payen. 
Carbon . . . 50-00 44-80 

Hydrogen . . 5-55 6-20 

Oxygen . . . 44-45 49-0 



100 100* 

In both these analyses the hydrogen is very nearl}' 8 times that of 
the oxygen. All these substances, therefore, may be represented by 
carbon and water, though the woody fibre of Dr. Prout contains 5 per 
cent, more carbon than the cellular matter of Payen. 

If we calculate the number of equivalents of each element contained 
in these two varietiesf of vegetable fibre composed as above exhibited, 
we find in the one 12 of carbon, 8 of hydrogen, and 8 of oxygen ; in 
the other, 12 of carbon, 10 of hydrogen, and 10 of oxygen. They may, 
therefore, be conveniently represented by the following formulas : 

Woody Fibre by Cjg Hg Cg 

Cellular Fibre. ... by C12 H^j C,o 
It is not unlikely that both of these forms of matter may exist, as 
well in the perfect wood of trees as in the less consolidated pith of the 
elder, or in the fibres of cotton — and that they may occur intermingled 
also in varying proportions with other substances, containing hydrogen 
in excess. t 

in its natural state, is a fact to which it will be important to advert when wc consider here 
after the chemical changes which the food undergoes in the interior of the plant. 
* Mey en' s JaJiresbericht, 1839, p. 10. 

t This is done very simply by dividing the carbon by 6, and the oxygen by 8 (see page 
36), thus — 

Carbon - - - 50 -^ 6 = 833 C which numbers ) 12 
Hydrogen • • 5 5.5 = 5-55 ^ are to each [ 8 
Oxygen - - ■ 44-45 -7- 8 = 55 5 ( other as 3 8 
I The existence of a variety of cellular fibre identical in constitution with common starch, 
as this of Payen is, (see subsequent section, p. 106,) was previously rendered probable by 
the observations of Dr. Schleiden, that the embryo of the Scholia lati/olia, consisting of 
pores and vessels, the sides of which exhibit distinct concentric layers, is entirely soluble 
in water, with the exception of the outer rind ; and that its solution becomes blue on the 
addition of iodine. It would appear as if the cellular substance were in this case wholly 
composed of Starch. (Poggendorf's Annalen, xliii., p. 398.) It may, however, be in such a 
state of tenuity in the embryo of this plant, as to be easily changed "into starch by the action 
of hot water ; and it is still by no means certain that the cellular fibre analyzed by Payen 
may not also have undergone a change by the treatment to which it was previously subject- 
ed. I am unable, however, to speak decidedly on this subject, as I have not seen the de- 
tails of M. Payen's several papers. (See subsequent section, on the mutual transforinattons 
of tcoody fibre, starch, gum, and sugar, p. 112.) 



106 PER CENTAGE OF WOODY FIBRE IN PLANTS. 

I have spoken of these varieties of woody fibre as constituting a large 
portion of the entire mass of vegetable matter produced during tlie 
growth of plants. That such is tiie case in the more gigantic vegetable 
productions, of which the great forests consist, is sufficiently evident, 
and so far the general statement is easily seen to be correct. It is also 
true of the dried stalks of the grasses and the corn-growing plants, of 
which it forms nearly one-half the weight, — but in roots and some 
plants which are raised for food, the quantity of woody fibre, especially 
in the earlier stages of their growth, is comparatively small.* Thus in 
the beet root it forms only 3 per cent, of the whole weight when taken 
from the ground. If suffered to remain in the soil till it becom.es old, 
or if the growth be very slow, the beet becomes more woody, as many 
other roots do, and the ([uantity of ligneous fibre increases. 

§ 2. Starch — its constitution and properties. 

Next to woody fibre, starch is probably the most abundant product ofll 
vegetation. To the agriculturist it is a substance of much more interest 
and importance than the woody or cellular fibre, from the value it pos- 
sesses as one of the staple ingredients in the food of man and animals — 
and from its forming a large portion of the weight of the various grains 
and roots which are the principal objects of the art of culture. 

1°. When the flour of wheat, barle3^ oats, Indian corn, &c., is mixed 
up into a dough with water, and this dough washed on a linen cloth 
with pure water, a milky liquid passes through, from which, when set 
aside, a white powder gradually falls. This white powder is the starch 
of wheaten or other flour. 

2^. When the pith of the sago palm is washed, in a similar manner, 
with water upon a fine sieve, a white powder is deposited by the milky 
liquid which passes through. This, when collected, forced through a 
metal sieve to granulate (or corn) it, and dried by agitation over the 
fire, is the sago of commerce. _. 

' The following table shows the per centage of woody fibre contained in some commoa 
plants in the green state, and when dried in the air, and at 212° : 

IN THE GREEN STATE. 

Dried in the air. Dried at 212°. Woody fibre. Water, 
percent. percent. percent, percent 

Barley straw, ripe 50 — — — 

Oat straw, do, — 47 — — 

Maize straw, do. 24 — — — 

Stalks of the field pea • ... — — 10)^ 80 

Eield bean straw 51 — — — 

White turnip — — 

Common beet (beta vulgaris) - — — 

Young twigs of common furze - — — 

Rape straw, ripe — 55 

Tare straw, do, 37 — 

Vetch plant (V. saliva) - - - 42 — 

Do. (V. cracca) in flower — — 

Do. (V. narbonensis) do. — — 

White lupin, in flower, 
Lucerne, in flower, 
Rye grass, do. - • 
Red clover, do. - • 
White clover, do. - • 
Trefoil (medium) do. 
Sainfoin (esparsette) - 
Trefoil (agrariunr.) in flower 
Do. (rubens) do. 



3 


92 


3 


86 


24 


50 


12K 


77 


lO'A 


77]4 


&>i 


68 


U'A 


80 


7 


86 


9 


73 


11 


68 


7 


79 


4>i 


81 


S}i 


73 


7 


76 


12 


68 


15 


60 



PREPARATION AND DECOMPOSITION OF STARCH. 10''' 

3°. When the raw potato is peeled and grated on a fine grater, and 
the pulp thus produced well washed with water, potato starch is ob- 
tained in the form of a fine white powder, consisting of rounded, glossy 
and shining particles. 

4°. When the roots of the Maranta Arundinacea of* the West India 
Islands are grated and washed like the potatoe, they yield the arrow 
root of commerce. From the root of the Manioc, the cassava is pro- 
cured by a similar process, and this, when dried by agitation on a hot 
plate, is the tapioca of the shops. By this method of drying, both sago 
and tapioca undergo a partial change, which will be explained in a sub- 
sequent section (see p. 113.) 

The substances to which these several names are given are, when 
pure, similar in their properties, and identical in their chemical consti- 
tution. They are all colourless, tasteless, without smell, when dry 
and in a dry place may be kept for any length of time without under- 
going alteration, are insoluble in cold water or alcohol, dissolve readily 
in boiling water, giving a solution which gelatinizes (becomes a jelly) 
on cooling — and in a cold solution of iodine* they all become blue. 

When dried at 212°, they consist, according to Dr. Prout, with whose 
analysis those of other chemists agree, of 

Carbon 44*0 per cent., or 12 atoms. 

Hydrogen .... G'2 per cent., or 10 atoms. 
Oxygen ..... -49*8 per cent., or 10 atoms. 

100 
Starch, therefore, may be represented by the formula C12 Hjo O,o, 
which is identical with that deduced in the preceding section for the 
cellular fibre of Payen. Both substances, therefore, contain the same 
elements (carbon, hydrogen and oxygen), united in the same propor- 
tions, and in both, as well as in the common fibre of wood, tKe hydrogen 
and oxygen exists in the proportion to form water. 

That starch constitutes a large portion of the weight of grains and roots, 
usually grown for food, will appear from the following table, which ex- 
hibits the quantity present in 100 lbs. of each substance named : 

Starch per cent. 

Wheat flour 39 to 77 

Rye ♦' 50 to 61 

Barley ♦' 67 to 70 

Oatmeal 70 to 80 

Rice flour 84 to 85 

Maize •' 77 to 80 

Buckwheat 52 

Pea and Bean meal 42 to 43 

Potatoes, containing 73 to 78 of water, . 13 to 15 

It thus exists most largely in the seeds of plants, and in some roots. 
It is frequently deposited, however, among the woody fibre of certain 
trees, as in that of the willow, and in the inner bark of others, as in 

* Iodine is a solid substance, of a lead-grey colour, possessed of a peculiar powerful 
odour, and forming when heated a beautiful violet vapour. It exists in small quantity in sea 
water, and in some marine plants. Its solution in water readily shows the presence of 
starch, by the blue colour it imparts to it. 



108 VARIETIES OF GUM. 

those of the beech and the pine.* Hence the readiness with which a 
branch of the willow takes root and sprouts, and hence also the occa- 
sional use of the inner bark of trees for food, especially in northern coun- 
tries, and in times of scarcity. In some roots which abound in sugar, 
as in those of the beet, the turnip, and the carrot, only 2 or 3 per cent, 
of starch can be detected. 

§ 3. Gum — its constitution and properties. 

The variety of gum with which we are most familiar is gum arabic, 
or Senegal, the produce of various species of acacia, which grow in the 
warmer regions of Asia, Africa, and America. It exudes from the 
twigs and stems of these trees, and collects in rounded more or less 
transparent drops or tears. It is also produced in smaller quantities in 
many of our fruit trees, as the apple, the plum, and the cherry ; it is 
present in some herbaceous plants, as in the althaea and malva officinalis 
(common and marsh mallow) ; and it exists in lint, rape, and many 
other seeds. When treated with boiling water these plants and seeds 
give mucilaginous solutions. 

Many varieties of gum occur in nature, but they are all characterised 
by being insoluble in alcohol, by dissolving or becoming gelatinous in 
hot or cold water, and by giving mucilaginous — viscid and glutinous — 
solutions, which may be employed as a paste. 

Three distinct species of gum have been recognised by chemists : 

1°. Arahin — of which gum arable and gum Senegal almost entirel 
consist:. It is readily soluble in cold water, giving a viscid solution, usu 
ally known by the name of the inucilage of gum arable. 

2°. Cerasin — which exists in the gum of the cherry-tree. It is inso- 
luble in cold water, but dissolves readily in boiling water. When thus 
dissolved it may be dried without losing its solubility, and is therefore by 
boiling supposed to be changed into arabin. 

3°. Bassorin — existing in what is called bassora gum — and forming 
a large portion of gum tragacanth.f It swells and becomes gelatinous in 
cold water, but does not dissolve in water either cold or hot. 

By these characters, the three kinds of gum are not only readily dis- 
tinguished, but may be easily separated from each other. Thus if a 
native gum or an artificial mixture contain all the three, simple steeping 
in and subsequent washing with cold water, will separate the arabin — 
boiling water will then take up the cerasin, and the bassorin will remain 
behind. 

These different kinds of gum all possess the same chemical constitu- 
tion. According to the analyses of Mulder, they consist of 
Carbon . . . 45*10 per cent., or 12 atoms. 
Hydrogen . . 610 " or 10 " 

Oxygen . . . 48-80^: ** or 10 " 

100 

* Its presence is readily detected in such wood by a drop of the solution of iodine — which 
^ives a permanent blue to starch, but to the woody fibre only a brownish stain. 

t This gum exists along with starch in the roots of the various species of orchis, especially 
of those which are used for making salep (Meyen). 

X Berzelius Arsberiittelse, 1839, p. 443. 






VARIETIES A.ND CONSTITUTION? OF SUGAR. 109 

In these analyses, as in those of starch and woody fibre, we see that 
the per centage of oxygen is equal to that of the hydrogen muItipHed by 
8, and consequently that these two elements are, as already stated, in 
the proportion to form water. But we see also that the carbon is in the 
proportion of 12 atoms or equivalents to 10 of each of the other con- 
stituents, and therefore gum may be represented by Cjg H, ^ O —a 
formula which is identical with that already given lor starch and cellu- 
lar fibre. 

It appears, therefore, that not only may gum, starch, and cellular fibre be 
represented by carbon and water, but that they all consist ofcarbm and 
the elements oftcater, united together in the same jyroportions. ■ 

Gum not only exists in many seeds, and exudes as a natural product 
from the stems and twigs of many trees, but is also contained in the 
juices of many other trees, from which it is not known to exude ; and in 
the sap of most plants it may be detected in greater or less quantity. It 
may be considered, indeed, as one of those substances which are pro- 
duced most largely and most abundantly in the vegetable kingdom, 
since, as will hereafter appear, it is one of those forms of combination 
through which organic matter passes in the interesting series of changes 
It undergoes during the development and growth of the plant. 

§ 4. Of Sugar — its varieties and chemical constitution. 
1°. Cane Sugar.— Sugar, identical in constitution and properties with 
that obtained from the sugar-cane, and generally known by the name of 
cane-sugar, exists in the juices of many trees, plants, and roots. In the 
United States of North America the juice of the maple tree is extensive- 
ly collected in spring, and when boiled down yields an abundant supply 
of sugar. In the Caucasus that of the walnut is extracted for the same 
purpose. The juice of the birch also contains sugar, and it may be ob- 
tained, in lesser quantity, from the sap of many other trees. In the 
juice of the turnip, carrot, and beet, it is also present, and in France and 
Germany the latter root is extensively cultivated for the manufacture of 
beet sugar. In the unripe grains of corn, at the base of the flowers of 
many grasses and clovers when in blossom, and even in many small 
roots, as in that of the quicken or couch-grass (triticum repens), the pre- 
sence of sugar may likewise be readily detected. 

Sugar is principally distinguished by its agreeable sweet taste. 
When pure, it is colourless and free from smell. It dissolves readily 
in alcohol and in large quantity in water. The solution in water, when 
much sugar is present, has an oily consistence, and is known by the name 
lof syrup. From this syrup the sugar gradually deposits itself in the 
iform of sugar candy. If the syrup be boiled on too hot a fire, it chars 
shghtly, becomes discoloured, and a quantity of molasses is formed. 
Pure cane-sugar, free from water, consists of 

Carbon . . . 44-92 per cent., or 12 atoms. 
Hydrogen . . 6-11 " or 10 " 

Oxygen . . . 48-97 " or 10 '? 

100 
If we compare these numbers with those given for starch and gum in 
the preceding sections, we see that they are almost identical— so that 
10 



110 CANE, GRAPE, MANNA, AND LIQUORICE SUGARS. 

cane-sugar also contains oxygen and hydrogen in the proportions to form 
water, and may likewise be represented by the formula C,3 Hiq Ojo. 
2°. Grape sugar. — In the juice of the grape a peculiar species of su- 
gar exists, which, in the dried raisin, presents itself in the form of little 
rounded grains. The same kind of sugar gives their sweetness to the 
gooseberry, the currant, the apple, pear, plum, apricot, and most other 
fruits. It is also the sweet substajice of the chesnut, of the brewers* 
wore, and of all fermenf.ed Tujiiors, and it is the solid sugar which floats 
in rounded grains in liquid honey, and which increases in apparent 
quantity as the honey, by keeping, becomes more and more solid. 
■ Grape sugar has nearly all the sensible characters of cane sugar, with 
the exception of being less soluble in water and also less sweet, — 2 parts 
of the latter imparting an equal sweetness with 5 of the former. 

In chemical constitution they differ considerably. Thus grape sug; 
dried at 250° F., consists of 

Carbon . . . 40-47 per cent., or 12 atoms. 
Hydrogen . . 6-59 " or 12 " 

Oxygen . . . 52-94 " or 12 " 



a| 



100 

The oxygen here is still eight times greater than the hydrogen, and, 
therefore, in this variety of sugar also, these elements exist in the pro- 
portioiis to form water. But for every 12 equivalents of carbon, dry 
grape sugar contains 12 of hydrogen and 12 of oxygen. It is conse- 
quently represented by Cto Hjo 0,2, and contains the elements of two 
atoms of water (H2 Og) more than cane sugar.* 

• 3°. Manna sugar, sugar of liquorice, S^v. — Besides the cane and grape 
sugars which occur in large quantity in the juices of plants, there are 
other varieties which occur less abundantly, and are therefore of less in- 
terest in the study of the general vegetation of the globe. Among these 
is manna, which partly exudes and is partly obtained by incisions from 
certain species of the ash tree which grow in the warmer countries of 
Southern Europe (Sicily and Italy), and in Syria and Arabia. It also 
exists, it is said, in tlie juice of the larch tree, of common celery, and of 
certain trees which are met with in New South Wales. Liquorice root 
also contains a species of black sugar, which is known in this country 
under the names of Spanish and Italian juice, from the countries where 
it is grown. In the mushroom and o\her fungi a colourless variety, ap- 
parently peculiar, lias also been met with, — and milk owes its sweet- 
ness to a species of sugar formed in the interior of tlie animal along with 
the other substances which the milk contains. 

These several kinds of sugar difler more or less, not onl}' in sensible 
and chemical properties, but also in chemical constitution, from the more 
abundant cane and grape sugars — but they form too smalJ a part of the 
general products of vegetation, and are of too little consequence in practi- 

• Solutions of cane and grape sugar arc readily distinguished from each other by the fol- 
lowing chemical characters: — I. If the solution be heated and a few drops of sulphuric acid 
then added, cane sugar will be decomposed, blackened, and made to fall as a black or brown 
powder — while a solution of grape sugar will at the most be only slightly discoloured. 2. If, 
instead of sulphuric acid, caustic potash be employed, the cane sugar will be unchanged, 
While the grape sugar will be blackened and thrown down. 



C, 2 


H3 


Os 


Ci2 


Hi 


Olo 


C,a 


Hi 


0,0 


Ci2 


Hi 


Oio 


Cl2 


H 1 


Oio 


Cl 2 


H12 


012 



MUTUAL P.ELATIOiNS OF V.'OODY TIBRK, STARCH, GUM, ETC. Ill 

cal agriculture to render it necessary (o do more than thus shortly ad- 
vert to their existence.* 

§ 5. Mutual relations of woody fibre, starch, gum, and sugar. 
It may be interesting now to consider for a moment the mutual rela- 
tions of the several substances, woody fibre, starch, gum, and sugar — 
above described — which occur so largely in the vegetable kingdom, and 
are serviceable to man for so many different purposes. These relations 
will be best seen on comparing the formulae by which they are respec- 
tively represented. Thus — 

Woody Fibre (lignin) is represented by 

Cellular Fibre (according to Payen) by 

Starch (dried at 212° F') by 

Gum (any of the 3 varieties) by 

Cane Sugar (free from water) by 

Grape Sugar (dried at 130° F.) by 

In these formulae we observe — 

1°. That the eqivalents of the oxygen are equal to those of the hydro- 
gen in all the formulae, and, therefore, that all these substances may be 
supposed to consist of carbon and water. 

2°. The formulae for cellular fibre, starch, gum, and cane sugar, are 
identical. They consist of the same elements united together in the same 
proportions. 

This is one of those facts which not only appear very remarkable to 
the unlearned, but are scarcely capable of being clearly comprehended 
and explained, even by those who have most profoundly studied this 
branch of natural science. Starch and sugar — how diiferent their 
properties I how unlike their uses ! how uiiequal their importance to the 
human race I yet they consist of the same weights of the same substances, 
difi'erently conjoined. The skilful architect can put together the same 
proportions of the same stone and cement — and the painter can combine 
the same colours so as to produce a thousand varied impressions on the 
sense of sight. In the hand of Deity matter is infinitely more plastic. 
At His bidding the same ])articles can unite in ihe same quantity so as 
to produce the most unlike impressions — and on all our senses at once. 

3°. A knowledge of the above close relations in composition, among 
a class of substances occurring so abundantly in the vegetable kingdom, 
imparts a degree of simplicity to our ideas of this otherwise complicated 
subject. It does not appear so mysterious that we should have woody 
fibre, and starch, and gum, and sugar, occurring together in variable 
quantities, when we know that they are all made up of the same ma- 
terials, in the same or nearly the same proportions — or that one of these 
should occasionally disappear from a plant, to be replaced in whole or 
in part by another. 

* For a list of plants from which sugar has been extracted, see Thomson's OrganieChemis- 
/ry(1838), p. 647. 

t Crystallized cane sugar (sugar candy) loses 5-3 per cent, of water in favourable circum- 
stances. This is equal tonne equivalent (HO), so that if dry sugar be C12H10O10, crystallized 
sugar is C 12 Hii On — or C12 Hio Oio-f-HO, since there is no doubt that this one equivalent of 
the hydrogen and oxygen exists in crystallized sugar in the state of water. Tn like manner, 
crystaUized honey or grape sugar— as it occurs in honey or in the dried grape — loses 9 per 
cent, of water when heated to 2.50° F. This is equal to two equivalents (2HO), ao that crys- 
tallized grape sugar is represented by C12 Hu O.4 or C12 His Oi:.-^2HO. 



112 MUTUAL TRANSFORMATIONS OF STARCH, GUM, ETC. 

A further question, however, arises in our minds. We naturally ask, 
— does nature, in thus removing one of these compounds, and supplying 
its place by another, actually form from its elements the new substance 
introduced, or does she produce it by a mere change or transformation 
of those previously existing. A satisfactory reply to this question may 
be derived from the facts detailed in the following section. 

§ 6. Mutual transformations of ivoody fibre, starchy gum, and sugar. 

I. WOODY FIBRE. 

1°. Action of heat. — If wood be reduced to the state of fine saw-dust, be 
then boiled in water to separate everything soluble, afterwards dried by 
a gentle heat, and then heated several times in a baker's oven, it will be- 
come hard and crisp, and may be ground in the mill into a fine meal. The 
powder thus obtained is slightly yellow in colour, but has a taste and 
smell similar to the flour of wheat ; it ferments when made into a paste 
with yeast or leaven, and when baked gives a light homogeneous bread. 
Boiled with water, it yields a stiff tremulous jelly, like that from 
starch (Autenrieth. — Schiibler, Agricultur Chemie, i., p. 224.) B3' the 
agency of heat, therefore, it appears thai the ivoody fibre may be changed 
into starch. 

2°. Action of sulphuric acid. — If to three parts of the sulphuric acid 
of the shops (oil of vitriol) one part of water be added, and a portion of 
delicate woody fibre be immersed in it for half a minute, and the whole 
then rubbed in a mortar with a few drops of a solution of iodine — the 
woody fibre will assume a blue colour, showing that it is in part at least 
changed into starch* (Schleiden). 

Again, if three parts of fine saw-dust or of fragments of old linen be 
rubbed in a mortar with four of the sulphuric acid of the shops added 
by degrees — it will, in a quarter of an hour, be rendered completely so- 
luble in water. If the solution in water be freed from acid by chalk, and 
then evaporated, a substance resembling gum arable is obtained (Bra- 
connot). According to Sclileiden, the fibre may be seen under the mi- 
croscope gradually to change from without inwards, first into starch and 
then into gum. 

Further, if this gum be digested with a second portion of sulphuric 
acid diluted with 8 or 10 times its weight of water, it will be gradually 
converted into^ro^pe sugar ; or the fibre of wood or linen may be changed 
directly into sugar by tlje prolonged action of dilute sulphuric acid. 

3°. Action of jyotash. — If saw-dust be mixed with from two to eight 
times its weight of hydratef of potash and as much water, and boiled 
till a crust forms on the surface, and if dilute sul|)lmric acid be then added 
till the whole is slightly sour, the undestroyed woody fibre will give an 

* It will be recollected that starch is characterized by giving a blue colour with a solution of 
iodine (see p. 107). 

The simplest way of trying this experiment is, to take a quantity of clean cotton — to wet 
it with water, squeezing out again as much as possible — then to spread it out upon a flat dish 
and moisten it quickly and thoroughly with Uie acid diluted as above. After half a minute, 
add the solution of iodine, stir quickly with a glass rod, and immediately add water, when 
the blue compound of iodine and starch will speedily deposit itself —{Schleiden, Pog. Annal. , 
xliii., p. 396.) 

t Hydrate of potash is the caustic substance which is obtained by boiling common pearl- 
ash with quick lime. 



ACTION OF HEAT ON STARCH. 113. 

instantaneous deep blue on the addition of iodine, showing that starch 
has been formed. 

Woody fibre, therefore, may be changed into starch, either by the un- 
aided action of heat, by that of sulphuric acid, or by boiling with caustic 
potash, — and the starch thus produced may be further transformed, first 
into gum and then into grape sugar, by the prolonged action of dilute 
sulphuric acid, assisted by a moderate heat. 

II. STARCH. 

1°. Action of heat. — When flour, potato, or arrow-root starch is 
spread out upon a tray, then introduced into an oven and gradually 
heated to a temperature not exceeding 300° F., it slowly changes, ac- 
quires a yellow or brownish tint according to the temperature employed, 
and becomes entirely soluble in cold water. It is changed into gum. 
Under the names of starch-gum, or British-gum, this substance is large- 
ly manufactured in this country, and is successfully substituted for gum 
arable by the calico-printers in thickening many of their colours.* 

The gum thus prepared not unfrequently also possesses a sweet taste, 
from the further change of a portion of the gum into sugar. 

2°. Action of water. — When starch is dissolved in boiling water, and 
is then allowed to stand in the cold either in a close vessel or exposed to 
the air, it gradually changes into gum or sugar. The process, however, 
is slow, and months must elapse before the whole of the starch is thus 
spontaneously transformed in the presence of water (De Saussure). It 
takes place more rapidly when starch and water are boiled together for 
a length of time. 

3°. Action of sulphuric acid. — From what has been already stated in 
regard to the action of this acid on woody fibre it will readily be supposed 
that native starch, of any variety, is likely to undergo transformation 
when subjected to its influence. 

In reality, if 50 parts of starch, 12 of sulphuric acid, and 139 of water 
be taken, and if the starch be thoroughly moistened with a portion of the 
water, and then poured into the mixture of the acid with the remainder 
of the water, and heated to 190° F., the starch will be entirely convert- 
ed into gum. By further and more prolonged heating this gum is 
changed into grape sugar. The gum or sugar may be obtained in a 
separate state by adding to the solution either chalk or lime, which will 
combine with and carry down the acid.f One hundred pounds of starch 
treated in this way will yield from 105 to 122 lbs. of dry grape sugar. 

The rapidity with which this transformation takes place depends 
partly upon the temperature and partly upon the proportion of acid em- 
ployed. Thus 100 lbs. of starch mixed with 600 of water and 10 of 
sulphuric acid, will be converted into grape sugar by boiling for seven 
I hours. If by increasing the pressure the temperature be raised to 250° 
F., the transformation will be effected in afe^v minutes. With only one 

* During the baking of bread this conversion of starch into gum takes place to a consider- 

1 able extent. Thus Vogel found that flour which contained no gum gave, when baked, a 

I bread of which 18 per cent., or nearly one fifth of the whole weight, consisted of gum. 

Thus one of the effects of baking is to render the flour-starch more soluble, and therefore (7) 

•■ more easily digestible. 

t It forms gypaum with it (sulphate of lime) which is a compound of lime and sulphuric 
I acid. 



in CHANGE OF CANE INTO GRAPE SUGAR 

pound of acid and the same quantity of starch and water, the change 
will be effected in three hours by a temperature of 230° F. This mode 
of converting potato starch into grape sugar is said to be extensively 
practised in France, for the purpose of subsequently fermenting the 
sugar and converting it into brandy. 

111. GUM. 

Action of sulphuric acid.— ir powdered gum arable be rubbed in a 
mortar with the sulphuric acid of the shops, a brownish solution is ob- 
tained, which, when diluted with water and treated with chalk, yields a 
gummy substance similar to that obtained in the same way from starch 
and woody fibre. Prolonged digestion with diluted acid converts a por- 
tion of this gum into sugar.— [Berzelius, Traitede Chemie, (1831), v., 
p. 217.] 

IV. CANE SUGAR. 

1°. Action of heat.— When crystallized cane sugar is heated to 320° 
F. it melts, and if the temperature be raised to 360° F. it gives off two 
atoms of water and is changed into caramel. This caramel is an un- 
rrystaUizable sugar, which is generally present in artificial syrups, and 
is often of a brownish colour. It contains the elements of an atom of 
water less than cane sugar, and is represented by C,3 Hg Og. It is 
not known to occur in the natural juices of plants. 

2°. Action of sulphuric acid.— When cane sugar is digested with di- 
lute sulphuric acid, aided by a gentle heat, it is rapidly converted into 
grape sugar. The acid of grapes (tartaric acid) and many other vege- 
table acids produce a similar change. 

It is obvious that this conversion of cane into grape sugar can only 
take place in the presence of water, inasmuch, as has already been 
shown (p. 110), grape sugar contains the elements of two atoms ot water 
more than cane sugar, or 

Cane sugar. Water. Dry grape sugar. 



We may revert now to the question with which we concluded the 
preceding section. Since these different substances are so closely allied 
in chemical constitution, and occur so often in connection with each 
other in the vegetable kingdom, does nature, when her purposes demand 
the change, actually transform them, the one into the other, in the inte- 
rior of the plant? The answer may now be safely given, that she cer- 
tainly does. What we can so readily perform by our rude art may be 
still more easily effected in the living vegetable. That which is starch 
or gum in one part of the plant, may become cane or grape sugar in 
another, and woody fibre in a third. Thus by re-arranging the same 
kind and quantity of the several elements, may the various and unhke 
forms of matter which constitute the main products of vegetation be 
readily produced. , 

Still the facility is only apparent. We can assure ourselves ot the 
fact of such conversions, because we can at will induce them. But who 
operates upon these substances in the interior of the plant? Whose 
mind and will directs these changes— prescribing when, where, and m 



GRAPE SUGAR ALO.NE FERMENTS. 115 

what order they shall take place ? How much depends upon the re- 
fined and little understood mechanism of the vegetable structure — how 
much on the living principle itself! What is this living principle — 
how can it direct !* 

§ 7. Of the fermentation of starch and sugar — and of the relative circum- 
stances under which cane and grape sugars generally occur in nature. 
It will be of use to us, in connection with the above transformations, 
to advert to the property possessed by starch and nearly all the known 
varieties of sugar of entering into iermentation under favourable cir- 
cumstances. When flour is made into a paste with leaven or yeast it 
begins to rise and ferment, — sooner or later, according to the kind of 
flour and the quantity of ferment added. When to a decoction of malt 
or to a solution of starch or of cane or grape sugar in water, a portijon of 
yeast is added, fermentation is speedily induced ; and if not arrested by 
unfavourable circumstances it will continue until the whole of the 
starch or sugar disappears. 

In all these cases it is grape sugar alone that undergoes fermentation. 
[Rose, Poggen. Annal.^ lii., p. 297.] The starch of the moist dough or 
of the solution is partially transformed into grape sugar before fermenta- 
tion commences. Such is the case also with tlie decoction of malt and 
with cane sugar. The fermentation commences soon after the first por- 
tion of grape sugar is formed, and proceeds more or less rapidly accord- 
ing as this transformation is more or less speedily effected. Hence, in 
the art of brewing, the necessity of cautiously regulating the tempera- 
ture by which this change of the starch and sugar is promoted and hast- 
ened. 

The fermentation itself is the result not of a mere transformation of 
one form of matter into another having the same elementary constitu- 
tion, but of a decomposition of one substance into two others unlike itself 
either in properties or in chemical composition. The grape sugar is re- 
solved into alcohol (spirits of wine), whicii remains in the liquid, and into 
carbonic acid, which escapes in the form of gas and causes the fermen- 
tation. Thus alcohol being represented by C4 He O2, and carbonic acid 
by CO., 

2 of alcohol = Cy H,2 O4 and 

4 of carbonic acid = C4 O3 make up 



1 of grape sugar ^^ ^\-i^i2^i2' 

It is an interesting fact that the cane and grape sugars occur in na- 
ture in circumstances which are entirely consistent with the statement 
in the preceding section, regarding the action of acids on the former 
variety of this natural product. Fruits contain grape sugar, which in- 
creases in (juantity as they ripen or become less sour. In the sugar 
cane, the beet root, and the maple and birch trees, cane sugar exists, 
but in their juices no acid is associated with the sugar. On the contra- 
ry, ammonia is known to be present in most of them along with the 
cane sugar. Hence it is inferred, that as in our hands and in our exper- 
iments cane sugar is changed by the agency of acids into grape sugar, and 

• "Canst thou by searching find out God— Canst tho'i find out the AJmighty unto perfection 1" 



116 SUBSTANCES CONTAINING NITROGEN. 

with remarkable ease by that acid which exists in the ripe grape, so it is 
in the interior of plants. "Where sugar occurs in connection with an acid 
in the juice of a plant, it is grape sugar in whole or in great part, be- 
cause in the presence of an acid body cane sugar cannot permanently ex- 
ist, but is gradually transformed into the sugar of grapes. It thus ap- 
pears also why fruits so readily enter into fermentation, and why, even 
when preserved with cane sugar, they will, in consetjuence of the acid 
they retain, slowly change the latter into grape sugar, and thus induce 
fermentation.* 

§ 8. Of substances lohich contain Nitrogen. — Gluten, Vegetaole 
AlhunieUy and Diastase. 
The substances described in the preceding sections consist of carbon, 
hydrogen, and oxygen only, and of them the great bulk of the vegeta- 
ble productions of the globe consists. But there are certain other sub- 
stances occurring along with starch and sugar, into which nitrogen enters 
as a constituent, and which, though not formed in the vegetable king- 
dom in very large (juantily, are yet of such interest and importance in 
other respects, as to make it necessary shortly to advert to them. 

1°. Gluten. — When the flour of wheat is made into a dough, and this 
dough is washed with water upon a fine sieve, a milky liquid passes 
through, from which starch gradually subsides. This has been already 
slated. But on the sieve, when the water ceases to go through milky, 
there remains a soft adherent, tenacious, and elastic substance, which 
can be drawn out into long strings, has scarcely any colour, taste, or 
smell, and is scarcely diminished by washing either with hot or with 
cold water. This substance is the gluten oi wheat. The flour of other 
kinds of grain also yield it by a similar treatment, though generally in 
much smaller quantity. This appears from the following table : — 
The grain of 

Wheat contains 8 to 35 per cent, of gluten. 
Rye .... 9 to 13 *' " " 

Barley ... to 6 " " 

Oats .... 2 to 5 " " 

When the moist gluten is dried in the air or at the temperature of 
boiling water, it diminishes much in bulk, and hardens into a brittle 
semi-transparent yellow substance resembling horn or glue. In this state 
it is insoluble in water, but dissolves readily in vinegar, in alcohol either 
cold or hot, and in solutions containing caustic potash, or soda, [the 
common pearl-ash or soda of the shops boiled witli quick-lime.] 

2°. Vegetable Albumen. — To the white of egg the name of albumen 
(albus, white) has been given by chemists. It possesses the well known 
property of coagulating or of forming a white solid insoluble substance, 
when it is heated either alone or after being mixed with water. 

When the starch has subsided from the milky liquid which passes 

* Milk also, in favourable circumstances, as when kept at a temperature of 100° F., Un- 
dergoes fermentation, and in some countries of Asia a spirituous liquor is prepared from 
mares' and asses' milk. In this case the milk first becomes sour, then the acid thus form- 
ed converts the milk sugar into grape sugar, and finally this sugcU' enters into fermenta- 
tion. This takes place more readily in consequence of the presence of the decomposing 
cheesy matter (casein) of the milk — as is shown by the fact that the introduction of a small 
quantity of the curd of milk into a solution of grape sugar will cause it to ferment. 



GLUTEN, VEGETABLE ALBUMEN, AND DIASTASE. ll? 

through the sieve in preparing the glutenof wheat, the water rests trans- 
parent and colourless above the white sediment. If this water be heated, 
it will become more or less troubled, and white films or particles will 
separate, which may be easily collected, and which possess all the pro- 
perties of coagulated albumen, or boiled white of egg. To this sub- 
stance the name of vegetable albumen has been given. ° When the fresh 
prepared glutenof wheat is boiled in alcohol a portion of albumen gene- 
rally remains undissolved, showing that water does not completely wash 
it out from the gluten. 

Vegetable albumen, when fresh and moist, has neither colour, taste, 
nor smell, is insoluble in water or alcohol, but dissolves in vinegar and 
in caustic potash or soda. When dry it is brittle, more or less coloured, 
and opaque. In the seeds of plants*, it exists only in small quantity— 
thus the grain of 

Wheat contains | to 1§ per cent. 
Rye ... 2 to 3| " 
Barley . . . ^V to i 
Oats • • • i to i '* 
It occurs more largely however iu the fresh juices of plants, in those 
of cabbage leaves, turnip roots, and many others. When these juices 
are heated the albumen coagulates and is readily separated. 

Gluten and vegetable albumen appear to be as closely related as sugar 
and starch are to each other. Like these two substances, they consist 
of the same elements, united together in the same proportions, and are 
capable of similar mutual transformations. According to the most re- 
cent analyses, those of Dr. Scheerer, they consist of 

Carbon = 54-76 
Hydrogen = 7-06 
Oxygen = 20-06 
Nitrogen = 18-12 

100 
When exposed to the air in a moist state these substances undergo de- 
composition. They ferment, emit a most disagreeable odour, and pro- 
i duce, among other compounds, vinegar and ammonia. 

The important influence which gluten and vegetable albumen are 
supposed to exercise over the nourishing properties of the different kinds 
of food in which they occur, will be considered in a subsequent part of 
these lectures.* 

3°. Diastase. — When cold water is poured upon barley newly malted 
and crushed, is permitted to remain over it for a quarter of an hour, is 
then poured off; filtered, evaporated to a small bulk over boiling water, 
I again filtered if necessary, and then mixed with much alcohol, a white 
tasteless powder fells — to which the name o^ diastase has been given. 

* There occur in the animal kingdom— ia the bodies of animala—three other forms of the 
jsubstance above described under the names of gluten and vegetable albumen. These are 
lalbumen or vyhite of egg, already mentioned,— casein, tlie curd of cheese,— and fibrin, the 
substance of the mtiscular fibre of animals. 

1^. Casein.- When the curd of cheese is well washed with water, and then boiled in 
alcohol to free it from oily matter, it forms the casein of chemists. While moist it is soft 
and colourless, but as it dries it hardens, assumes a yellow colour, and becomes semitrans- 
parent. Even when moist it is perfectly insoluble either in cold or in hot water. It is .siolu- 



IIQ PRODUCTI J>' OF DIASTASE. 

If unmalted barley be so treated no diastase is obtained. This sub- 
stance, therefore, is formed during the process of malting. 

If wheat, or barley, or potatoes, which by steeping in water yield no di- 
astase, be made to germinate (or sprout), and be afterwards bruised and 
treated as above, diastase will be obtained. It is therefore produced 

during germination. _.,.,,<, -i c- \ .!• 

If the shoot of a potato be cut ofrwitlim half an inch of its base, this 
lower portion, with the part of the potato to which it is immediately at- 
tached, separated from the rest— and the three parts (the upper portion 
of the shoot— the lower portion with its attached fragment of potato— 
and the remaining mass of the potato) treated with water,— only that 
])ortion will yield diastase in which the base of the shoot is situated. 
When a seed sprouts, therefore, tlm substance is formed at the base oj 
the germ, and there remains during its growth. 

If the same portion of the potato, or if the grain of barley or wheat is 

ble however, in water containing vinegar, or to which a little carbonate of potash or soda 
has beeTadded It may be kept for any length of lime in a dry place, without undergomg 
decay The changes undergone by old cheese are chiefly due to the oily and other sub- 
stances wifh wlrich the curd is mixed. It has been remarked, that when the gluten of whea! 
fslStfo^a length of time in a moist state it undergoes a kind of fermentation and gradually 
acauires the smell and taste of cheese (Rouelle.) .„ . ^ , , 

2" Sfn-When lean beef or mutton is long washed in wafer till it becomes colourless, 
and is then boiled in alcohol to separate the fat, a colourless, elastic, fibrous mass is obtained, 
which is the fibrin of chemists. In recently drawn blood it exists in the liquid stale but coa- 
gulaies spontaneously when exposed to the air, and forms the greater part of the clot of 
blood. It dissolves in a solution of caustic potash or of mire, and m yinegar 

^o Albumen.-Thm substance in the liquid state exists m the white of egg, and m the 
serum of the blood. It coagulates by heating to 160° F , or if previously mixed with water 

^VhSe'tlTref substances, in addition to their well Known sensible properties, are distin- 

guishe^ as^follows ^ in milk, is not coagulated by heating cdone-ihe addition of rennet or of 
alittleacidCvinegaror spirit of salt) is necessary, when it curdles readily. 
20 Uguidalbimen in white of egg, coagulates by heat alone, as when an egg .s put »nto 

^%o^^Uqmd fibrin in the blood coagulates by mere exposure to the air, or more rapidly by 

'^t£"t?rch and^'Sv tti'-three substances are mutually convertible by known means^ 
Tlmr/i6rS!if nnboilld, dissolves by digestion at 80° F. in a saturated soluuon of nitre, and 
ac luires the propeTties of liquid albumen; and if to liquid albumen a httle caustic potash be 
added, and afterwards much alcohol, it will be thrown down in the form and with the pro 

^AuTese substances appear to contain the same organic constituents in the same propor- 

^'Xu^sin-auU first showed the identity in chemical constitution of gluten and vegetable al- 
bumen -fPo- An , xl.. p. 253. ] Mulder afterwards proved a simHar identity between vege- 
S albumen and he white of egg, fibrin, and casein.-[Ann. de Cium. et. de Phys., Ixy p. 
§)I ] Mulder supposes them to differ from each other by the presence in unhke quantities 
of a small admixture of sulphur, phosphorus or phosphate of lime. 

ThoTe who are notfamililr wiJh the history and with the nature of chemical research, can 
form no idea of the time and labour which has by different chemists been expended on this 
one brar^ch The persevering industry of Dr. Mulder, of Rotterdam appeared to have 
deared up the entire subject by a long series of investigations and analyses,-[for an out- 
line of h"sVesults. see Berzelius Arsberaltlese, 1839, p. 61 l,]-when first Vogel,tJien Prosper 
Denis and latest Liebig and Dr. Scheerer. have arrived at diflTerent results. Our ideas are 
Sus ac'ain unfixed, and our partial generalizations set aside for future ?"]*^"^1«"«"- ,„^, . , 

Tle'analysis inserted in the text, as representing the composition of f 'f^"/"^/; f^^f"^ 
albumen is that given by Dr. Scheerer for the purest form oi fibrin. I have selected it in 
prefSence to the^result J either of Boussingault or of Mulder, because ,t is ^^e most recent 
and has been obtained with a knowledge of all the previous researches,— and assuming the 
SmLal id" ntlty of th^s entire group of substances, is the most likely to represent their 
SnsS on wi h aSuracy. It differs from the analysis of Mulder only m sfatmg the mtro- 
gen a 2 per cenl. higher than was done by that chemist. The recent ""P^°^^X«"'^ " .^.^ 
mode of determining the true quantity of nitrogen in organic substances, appear to justify 
us in expecting the result of Scheerer to be in this respect the more correct. 



DIASTASE CHANGES STARCH INTO SUGAr! 119 

examined, when the first true leaves of the plant have been fully 
formed and expanded, the diastas3 will be found to have in great part, 
if not entirely, disappeared. This substance, therefore, is first formed 
when the seed begms to sprout, performs a function which makes its 
presence necessary at the base of the germ, and which function being 
discharged when the true leaves are formed, it then disappears. Wha^t 
is the nature of this temporary function, why the diastase must reside at 
the base of the sprout in order to dischar£;e it, and why it should so early 
cease, will appear from a detail of the properties of this singular sub- 
stance. 

Properties of diastase.— m\\e solution obtained from malt be digested 
with potato, flour, or other starch, at a temperature between 120° and 
140° F., the latter will gradually dissolve and will form a colourless 
transparent solution. When this solution is carefully evaporated a yel- 
lowish white powder is obtained, perfectly soluble in water, to which 
the name of dextrine has been given, [because its solution turns to the 
n«-/i^ a ray of polarized light when passed through it.] This dextrine 
has the same composition as starch. It is merely starch changed or 
transformed in such a way as to become soluble in cold wat'er,— a 
• change analogous lo that which it undergoes by simply boiling in water. 

But if the digestion be continued after the starch is dissolved, the so- 
lution will gradually acquire a sweet taste, and if it be now evaporated 
It will yield, instead of dextrine, a mixture of gum and grape sugar. 
And if the digestion be still further prolonged, the Avhole of the starch 
will be converted into grape sugar only.— [See above, § 6, p. 113.] 

Thus diastase (like sulphuric acid) possesses the property of trans- 
forming starch entirely— first into gum, and then info grape sugar. The 
intermediate stage of dextrine has not been recognized in the action of 
sulphuric acid, nor is it easy to arrest the action of diastase exactly at 
this point— the most carefully prepared dextrine always containing a 
mixture of gum and sugar. One part of diastase will convert into sugar 
2000 parts of starch. ^ 

A solution of diastase, when allowed to stand, soon undergoes decom- 
position, and after being boiled, it has no further effect upon starch. It 
has not been analysed, because it is difficult to obtain it in a pure state. 
It contains nitrogen, however, for, when moistened and exposed to the 
air. It decomposes, and, among other products, yields ammonia.* 

The functions of diastase— one of the purposes at least for which it is 
produced in the living seed, and situated at the base of the germ— will 
now be in some measure understood. The starch in the seed is the food 
of the future germ, prepared and ready to minister to its wants when- 
ever heat and moisture concur in awakening it to life. But starch is it- 
self insoluble in water, and could not, therefore, accompany the fluid sap 
when It begins to move and circulate. For this reason diastase is 
tormed at the point where the germ first issues from the mass of food. 
Ihere it transforms the starch, and renders it soluble, so that the young 
vessels can take it up and convey it to the point of growth. When the 
starch IS exhausted its functions cease. It is then itself transformed and 

LecturfllLjV^sT"^*''^'^ ^^*^ ammonia contains nitrogen, being represented by NHs.-See 



1-20 ADAPTAT10>"S IN THE PR0DUCT10^'S OF DIASTASE. 

carried into the general circulation. Or when, as in the potato, much 
more starch is present than is in many cases requisite, its function ceases 
long before the whole of the starch disappears. Its presence is necessa- 
ry only until the leaves and roots are fully formed — when the plant is 
enabled to provide for itself, and becomes independent of the starch of 
the seed. When this period arrives, therefore, the production of dias- 
tase is no longer perceived. 

This I have said is one of the purposes which appears to be served by 
diastase in the vegetable economy. That it is the only one we have no 
reason to believe. There may be others quite as interesting which we 
do not as yet understand. This is rendered more probable by the fact 
that the diastase contained in one pound of malted barley is capable of 
converting into sugar live pounds of starch.* (Liebig.) And though 
at the temperature at which the seed germinates, more of this substance 
may be necessary to transform the same weight of starch than is re- 
quired in our hands, when aided by artificial heat, — yet as we never in 
the ordinary course of nature find any thing superfluous or going to 
waste, there is reason to believe that the diastase may be intended also 
to contribute directly to the nourishment and growth of the plant. As 
it contains nitrogen, it must be derived from the gluten or vegetable al- 
bumen of the seed ; and as a young plant of wheat, when already many 
inches from the ground, contains no more nitrogen than was originally 
present in the seed itself (BoussingauU), this diastase may only be the 
result of one of those transformations of which glutenf is susceptible, 
and by which it is rendered soluble, and capable of aiding in the pro- 
duction of those parts of the substance of the growing plant into which 
nitrogen enters as a necessary constituent. 

It may not be uninstructive if we pause here for a moment and con- 
sider the beauty of the arrangements we have just been describing. In 
passing through a new and interesting country we do not hesitate, at 
times, to stop and gaze, and leisurely admire. We cannot otherwise 
fully realize and appreciate its beauty. So in the domains of science, 
we cannot be ever hurrying on — we must linger occasionally, not only 
that we may more carefully observe, but that we may meditate and 
feel. 

You see how bountifully nature has provided in the seed for the nour- 
ishment of the young plant, how carefully the food is stored up for it, 
and in how imperishable a form — how safely covered also and protected 
from causes of decay ! For hundreds of years the principle of life will 
lie dormant, and for as many the food will remain sound and undimin- 
ished till the lime of awakening comes. Though buried deep in the 
earth, the seed defies the exertions of cold or rain, for the food ifcontains 
is unciiTected by cold and absolutely insoluble in water. But no sooner 

* It is the diastase in malt which dissolves the slarch of the barley in the process of brew- 
ing, but as the diastase contained in malt is sufficient to dissolve so large a quantity of starch, 
it is obviously a waste of labour to malt the whole of the barley employed. One of malt to 
three of barley would probably be sufficient in most cases to obtain a wort containing the 
whole of the slarch in solution. Advantage is taken of this property in the manufacture of 
the white beer of Louvain, and of other places in Flanders, and in Germany, where the light 
colour is secured by adding a large quantity of flour to a decoction of a small quantity of 
barley. 

t That diastase is merely ttansformed gluten we cannot say, because the exact chemical 
constitution of diastase is as yet unknown. 



VEGETABLE ACIDS. 121 

is the sleei)ing germ recalled to life, by the access of air and warmth 
and duly tempered moisture, than a new agent is sumiuoned to its aid, 
and the food is so changed as to be rendered capable of ministering to its 
early wants. The first movement of the nascent germ — (and how it 
moves, by what inherent or impartial tbrce, who shall discover to us ?) 
—is the signal for the appearance of this agent — diastase — of which, 
previous to germination, no trace could be discovered in the seed. At 
the root of the germ, where the vessels terminate in the farinaceous 
matter, exactly where it is wanted, this substance is to be found ; — there, 
and there only, resolving and transforming the otherwise unavailable 
store of food, and preparing it for being conveyed either to the ascending 
sprout or to the descending root. And when the necessity for its pre- 
sence ceases — when the green leaf becomes developed, and the root has 
fairly entered the soil— when the plant is fitted to seek food for itself — 
then this diastase disappears, it undergoes itself a new conversion, and is 
prepared in another form to contribute to the furtlier increase of the plant. 
How beautiful and provident are all these arrangements! — how plas- 
tic the various forms of organic matter in the hands of the All-Intelli- 
gent I — how nicely adjusted in time and place its diversified changes ! 
What an apparently lavish expenditure of forethought and kind previ- 
sion, in behalf even of the meanest plant that grows ! 

§ 9. Vegetable Acids. — Acetic acid, Oxalic acid, Tartaric acid, 
Citric acid, Malic acid. 
Another class of compound substances remains to be shortly consid- 
ered, — those, namely, which possess sour or acid properties, and which 
are known to be present in large quantity in many plants, and more 
especially in the greater number of unripe fruits. They do not, taken 
as a whole, form any large portion of the entire produce, either of the 
general vegetation of the globe or of those plants which are cultivated 
for food ; yet the growth of fruit — as in the grape, orange, and apple 
countries — is sufficiently extensive, and the general interest in the cul- 
tivation of fruit trees sufficiently great, to require that the nature of the 
substances contained in fruits, and the peculiar changes by which they 
are formed, should be in some measure considered and explained. 

I. ACETIC ACID. 

Acetic acid or vinegar is the most extensively diffused, and the most 
largely produced, of all the organic acids. It is formed during the ger- 
mination of seeds, and it exists in the juices of many i)lants, but it is 
most abundantly evolved during the fermentation, whether natural or 
artificial, of nearly all vegetable substances. When pure it is a colour- 
less liquid, having a well known agreeably acid taste. ^ It may be 
boiled and distilled over without being decomposed. The vinegar of the 
shops is generally very much diluted, but it can be prepared of such a 
strength as to freeze and Ijecome solid at 45° F., and to blister the skin 
and produce a sore when applied to any part of the body. When 
mixed with water it readily dissolves lime, magnesia, alumina, &c., 
forming salts called acetates, which are all soluble in water, and may, 
therefore, be readily washed out of the soil or of compost heaps by 
heavy falls of rain. 



122 PREPARATION OF ACETIC ACID. 

When perfectly free from water, acetic acid consists of — 
Carbon . . . 47*5 per cent., or 4 atoms 
Hydrojren . . 5-8 " or 3 " 

Oxygeii . . . 46-7 " or 3 " 

100 

It is therefore represented by the formula C4 H3 O3 — in which, as in 
those given in the preceding sections for starch, sugar, &c., the numbers 
representing the atoms of hydrogen and oxygen are equal, and conse- 
(piently these elements are in the proportion to form water. Hence, 
vinegar, like sugar, may be represented by carbon and water. 

Let us consider for a moment the several processes by which this acid 
is ugually formed. 

1°. By the distillation of wood. — This a method by which wood 
vinegar — often called pyroligneous acid — is prepared in large quantity. 
Wood which has been "dried in the air is put into an iron retort and distil- 
led. The principal products are vinegar, water, and tarry matter. 
The decomposition is of a complicated description, but by comparing 
the constitution of woody fibre with that of vinegar, we can readily see 
the nature of the changes by which the latter is produced. 
Woody Fibre is = C12 Hg Og 
3 of Vinegar are = C12 Hg O9 



Difference = H^ O, ; or the elements 

of one atom of water. One portion of the woody fibre, therefore, com- 
bines with the elements of an atom of water, obtained by the decompo- 
sition of another portion, and thus vinegar is produced. 

2°. Manufacture of Vinegar from Cane Sugar. — It is a well known 
fact in domestic economy, that if cane sugar be dissolved in water, a 
little vinegar added to it, and the solution kept for a length of time at a 
moderate temperature, the whole will be converted into vinegar without 
any sensible fermentation. This process is frequently followed in the 
preparation of household vinegar, and was formerly adopted to some ex- 
tent in our chemical manufactories. It will be recollected that we re- 
presented Cane Sugar by C12 H,o Oioj while 
3 of Vinegar = C12 Hg Og 



Difference Hj Oj ; or the elements 

of an atom of water, which cane sugar must lose in order to be convert- 
ed into vinegar^ Whether the change in this instance takes ])lace by 
the direct conversion of cane sugar into vinegar, or whether tlie former 
is previously transformed into grape sugar, has not been satisfactorily de- 
termined. 

3°. Manufacture of Vinegar from Alcohol. — In Germany, where 
common brandy is cheaper than vinegar, it is found profitable to manu- 
facture this acid from weak spirit. For this purpose it is mixed with a 
little yeast, and then allowed to trickle over wood shavings moistened 
with vinegar, and contained in a cask, the sides of which are perforated 
with holes for the admission of a current of air. By this method oxy- 
gen is absorbed from the air, and in 24 hours the alcohol in the spirit is 
converted into vinegar and water. 



TARTARIC ACID IN THE GRAPE. 123 

The explanation of this process is also simple, alcohol being repre- 
sented by C4 H, O.. Thus— 

Alcohol = C4 Hg O, ] ( Vinegar = C4 H3 O3 

4 ofOxFGEN = 0\ (__.' 3 of Water = H-, O^, 



Sum C^HeOcJ i Sum = C4 H^ Og 

4°. Production of Vinegar by fermentation. — When vegetable mat- 
ters are allowed to ferment, carbonic acid is given off and vinegar is 
formed. In such cases this acid is the result of a series of changes, du- 
ring which that i)ortion of the vegetable matter which has at length 
reached the state of vinegar has most probably passed through the seve- 
ral previous stages of grape, sugar, and alcohol. The carbonic acid, as 
has already been explained (p. 115), is given off during the fermentation 
o( the grape sugar, and the consequent formation of alcohol. 

To simple transformations, similar to those above described, we can 
trace the origin of the vinegar which is met with in the living juices of 
j)lants, and among the products of their decay. 

II.— TARTARIC ACID. 

The grape and the tamarind owe their sourness to a peculiar acid to 
which the name of tartaric acid has been given. It is also present, along 
with other acids, in the mulberry, in the berries of the sumach {rhus co- 
riarii), and in the sorrels, and has been extracted from the roots of the 
couch-grass and the dandelion. 

When new wine is decanted from the lees, and set aside in vats or 
casks, it gradually deposits a hard crust or tartar on the sides of the ves- 
sels. This substance is known in commerce by the name of argol, and 
when purified is familiar to you as the cream of tartar of the shops. It 
is a compound of tartaric acid with potash, and from it tartaric acid is 
extracted for use in medicine and in the arts. The principal use of the 
acid is in certain processes of the calico printers. 

The pure acid is sold either in the form of a white powder or of trans- 
parent crystals, which are colourless, and have an agreeable acid taste. 
It dissolves readily in water, and causes a violent effervescence when 
mixed with a solution of the carbonate of potash or of soda. As it has 
no injurious action upon the system, it is extensively used in artificial 
soda powders and effervescing draughts. When added in suflficienl 
quantity to a solution containing potash, it causes a white crystaUine 
powder to fall, which is cream of tartar (or bitartrate of potash), and from 
lime water it throws down a white chalky precipitate oi" tartrate of lime. 
Both of these compounds are present in the grape. 

Wlien perfectly free from water this acid consists of — 
Carbon , . . = 36*81 or 4 atoms. 
Hydrogen . . =: 3-00 or 2 atoms. 
Oxygen . . . = 60-19 or 5 atoms. 



100 
It is therefore represented by the formula C4 H2 O5. 

If we compare the nnmbers by which the atoms of hydrogen and ox- 
ygen in this acid are expressed, we see that these elements are not in the 
proportion to form water, and that this substance, therefore, cannot, like 



124 CONSTITUTION OF TARTARIC AND CITRIC ACIDS. 

SO many of those we have hitherto had occasion to notice, be rtpresenled 
by carbon and the elements of water alone. 
It may be represented by 

4 of Carbon . . = C^ ) 

2 of Water . . = Hr, Oo \ or, 4C+2H4-30 
and 3 of Oxygen . . =: ■ Oo S 



Tartaric Acid = 0411205 
And, though this mode of representation does not truly exhibit the con- 
stitution of the acid, inasmuch as we have no reason to believe that it 
really contains water as such — yet it serves 10 show very clearly that in 
the living plant this acid cannot be formed directly from carbon and the 
elements of water, as starch and sugar may, but that it requires also 
three atoms of oxygen in excess to every five of carbon and two of water. 
AVe shall, in the following lecture, see bow nicely Jhe functions of the 
several parts of the plant are adjusted, — at one period to the formation of 
this acid, and at another to its conversion into sugar during the ripening 
of the fruit. 

III. — CITRIC acid, or ACID OF LEMONS. 

This acid gives their sourness to the lemon, the lime, the orange, the 
cranberry, the red whortleberry, the bird-cherry, and the fruits of the 
dog-rose and the woody night-shade. It is also found in some roots, as 
in those of the dahlia pinnata, and the asarum europgeum {asarrabacca)^ 
and mixed with much malic acid, in the currant, cherrjs gooseberry, 
raspberry, strawberry, common whortleberry, and the fruit of the haw- 
thorn. 

When extracted from the juice of the lemon or lime, and afterwards 
purified, it forms transparent colourless crystals, possessed of an agreea- 
ble acid taste ; effervesces like tartaric acid with carbonate of soda, and 
like it, therefore, is much employed for effervescing draughts. With 
potash it forms a soluble salt, which is a citrate of potash^ and from lime 
water it throws down a white, nearly insoluble, sediment of aVra^e o/* 
lime^ which re-dissolves when the acid is added in excess. In combi- 
nation with lime it exists in the tubers, and with potash in the roots, of 
the Jerusalem artichoke. 

When free from water, citric acid consists of 

Carbon . . . . 41*49 = 4 atoms. 

Hydrogen . . . 3-43 = 2 atoms. 

Oxygen .... 55*08 = 4 atoms. 



100 
and is therefore represented by C4 Hg O4. 

This formula differs from that assigned to the tartaric acid only in 
containing one atom of oxygen less, O4 instead of O5. In the citric 
acid, therefore, there are 2 atoms of oxygen in excess, above what is 
necessary to form water with the 2 of hydrogen it contains. 

IV. MALIC ACID. 

The malic and oxalic acids are more extensively diffused in living 
plants than any other vegetable acids. If acetic acid be more largely 



CONSTITUTION OF MALIC AND OXALIC ACIDS. 125 

formed in r^ture, it is chiefly as a product of the decomposition of or- 
ganic matter, when it has already ceased to exist in, or to form part of, 
a living plant. 

Along with the citric acid, it has been already stated that the malic 
occurs in many fruits. It is found more ahundantly, however, and is the 
chief cause of the sour taste, in the imripe apple, [hence its name malic 
acid,] the plum, the sloe, the elderberry, the barberry, the fruit of the 
mountain ash, and many others. It is associated with the tartaric acid 
in the grape and in the Agave americana. 

This acid is not used in the arts or in medicine, and therefore is not 
usually sold in the shops. It i:s obtained most readily, in a pure state, 
from the berries of the mountain ash. It forms colourless crystals, 
which have an agreeable acid taste. It combines with potash, soda, 
lime, and magnesia, and forms maiates, and, in combination with one or 
more of these bases, it usually occurs in the fruits and juices of plants. 
The tnalate of lime is soluble, while the citrate, as already stated, is 
nearly insoluble, in water. This malate exists in large quantity in the 
juice of the house-leek {sempervivum tectorum), mihe Scdum tele])hium, 
the Arum maculatum, and many other juicy and fleshy-leaved plants. 

When perfectly free from water, the malic acid has exactly the same 
chemical constitution as the citric, and is represented by the same for- 
mula C4 H3 O4. These two acids, therefore, bear the same relation 
to each other as we have seen that starch, gum, and sugar do. They 
are what chemists call isomeric, or are isomeric bodies. We cannot 
transform them, however, the one into the other, by any known means, 
though there is every reason to believe that they may undergo such 
transformations in the interior of living plants. Hence probably one 
reason also why the malic and citric acids occur associated together in 
so many different fruits. 

V. OXALIC ACID. 

' This acid has already been treated of, and its properties and composi- 
tion detailed, in a preceding lecture (Lecture III., p. 47). It forms co- 
lourless transparent crystals, having an agreeably acid taste, and it 
effervesces with the carbonates of potash and soda, but on account of its 
poisonous qualities, it is unsafe to administer it as a medicine. It oc- 
curs in combination with potash in the sorrels, in rhubarb, and in the 
juices of many lichens. Those lichens which incrust the sides of rocks 
and trees, not unfrequently contain half their weight of this acid in com- 
bination with lime. It can be formed artificially by the action of nitric 
acid on starch, sugar, gum, and many other organic substances. 

When perfectly free from water, oxalic acid contains no hydrogen ; 
but consists of — 

Carbon . . . 33'75 = 9 atoms 

Oxygen . . . 66-25 — 3 *' 



100 
and it is represented by C^ O3. When heated with strong sulphuric 
acid, it is decomposed and resolved into gaseous carbonic acid^(COo) and 
carbonic oxide (CO) in equal volumes. This change is easily under- 
stood since CO. -|- CO = Co O3. 



126 STARCH CONVERTED INTO WOODT FIBRE. 

§ 10. General observations on the substances of which plants chiefly consist. 

It may be useful here shortly to review the most important facts and 
conclusions which have been adverted to in tlie present lecture. 

1°. The great bulk of plants consists of a series of substances capable 
of being represented by, and consequently of being formed in nature 
from, carbon and the elements of water only. Such are woody fibre, 
starch, gum, and the several varieties of sugar (p. 111). 

2°. Yet the crude mass of wood, as it exists in a full-grown 
tree, containing various substances in its pores, cannot be represented 
by carbon and the elements of water alone. It appears always to 
contain a small excess of hydrogen, which is greater in some trees than 
in others. Thus in the chesnut and the lime, this excess is greater than 
in the pines, while in the latter it is greater than in the oak and the ash. 
[For a series of analyses of different kinds of wood by Peterson and 
Schodler, see Thomson's Organic Chemistry, p. 849.] 

3°. These substances are, in many cases, mutually convertible even 
in our hands. They are probably, therefore, still more so in nature. 

It is to be observed, however,\hat all the transformations we can as 
yet effect are in one direction only. We can produce the above com- 
pounds from each other in the order of lignin or starch, gum, cane sugar, 
grape sugar — that is, we can convert starch into gum, and gum into 
sugar, but we cannot reverse the process, so as to form cane from grape 
sugar, or starch from gum. 

The only apparent exception to this statement with which we are at 
present acquainted, occurs in the case of starch. When this substance 
is dissolved in cold concentrated nitric acid, and then mixed largely with 
water, a siibstance [the Xyloidin of Braconnot] falls to the bottom, 
which is a compound of the nitric acid with woody fibre (Cja Hg Og.) 
[Pelouze, see Berzelius Arsberdttelse, 1839, p. 416.] In this instance, 
if the above observation is correct, there appears to be an actual con- 
version of starch into woody fibre. 

But what we are as yet unable to perform may, nevertheless, be easily 
and constantly eflfected in the living plant. Not only may what is starch 
in one part of the tree be transformed and conveyed to another part in 
the form of sugar,— -but that which, in the form of sugar or gum, passes 
upwards or downwards with the circulating sap, may, by the instrumen- 
tality of the vital processes, be deposited in the stem in the form of 
wood, or in the ear in that of starch. Indeed we know that such actu- 
ally does take place, and that we are still, therefore, very far from being 
able to imitate nature in her power of transforming even this one group 
of substances only. 

4°. Among, or in connection with, the great masses of vegetable mat- 
ter which consist mainly of the above substances, we have had occasion 
to notice a few which contain nitrogen as one of their constituents — and 
which, though forming only a small fraction of the products of vegetable 
growth, yet appear to exercise a most important influence in the general 
economy of animal as well as vegetable life. The functions performed 
by diastase in reference to vegetable growth, and to the transformations 
of organized vegetable substances, haVe already been in some measure 
illustrated,— we shall hereafter have an opportunity of considering more 



laiPORTANCE OF THE VEGETABLE ACID. 127 

fully t .e influence which gluten and vegetable albumen exercise ovei 
the general efficiency of the products of vegetation in the support of ani- 
mal life, and over (lie changes which these products must undergo, be- 
fore they can be. converted into the substance of animal bodies. lu a 
former lecture (Lecture IV., p. 66), I have had occasion to draw your 
attention to the comparatively small proportion in which nitrogen exists 
in the vegetable kingdom, and to show that it must nevertheless be con- 
sidered as much a necessary and constituent element in their composi- 
tion as the carbon itself; the very remarkable properties we have al- 
ready discovered in the compounds above mentioned strongly confirm 
this fact, and illustrate in a striking manner the influence of apparently 
feeble and inadequate causes in producing important natural results. 

5°. With the exception of acetic acid, which in constitution is closely 
related to sugar* and gum, all the acid substances to which it has been 
necessary to advert, contain an excess of oxygen above what is neces- 
sary to form water with the hydrogen they contain. Thus 

Vinegar = C4 H3 O3 contains no excess of oxygen. 

Tartaric Acid = C4 Ho O5 . . 3 of oxygen in excess. 
Malic Acid } r^ tt r\ r. 

iTRic Acid ^ 424 

Oxalic Acid = C2 O3 . . 3 

It requires a little consideration to enable us to appreciate the true im- 
portance of these and other organic acids, in the vegetable economy. At 
first sight they appear to form a much smaller part of the general pro- 
ducts of vegetation than is really the case. \Ve must endeavour to 
conceive the quantity actually produced by a single tree loaded with 
thousands of lemons, oranges, or apples, — or again, how much is formed 
during the growth of a single comparatively small plant of garden rhu- 
barb in spring, if we would obtain an adequate idea of the extent to 
which these acids are constantly formed in nature. On the other hand, 
we must recollect also that the greater portion of the acid of fruits disap- 
pears as they ripen, if we would understand the true nature of the in- 
terest which really attaches to the study of these substances, of the 
changes to which they are liable, and of the circumstances under which 
in nature these changes take place. 

6°. I will venture here to draw your attention for a moment to the na- 
ture and extent of that remarkable power over matter, which the chem- 
ist, as above explained, appears to possess. Such a consideration will 
be of value not only in illustrating how far we really can now, or may 
hereafter, expect to be able to influence or control natural operations, 
[see Lecture II., p. 32,] but what is probably of more value still, exhibit- 
ing the true relation which man bears to the other parts of creation ; and, 
in some measure, the true position he is intended to occupy among them. 

1°. We have seen that the chemist can transfortn certain substances 
one into the other, in a known order ; but that as yet he cannot reverse 
that order. Thus far his power over matter is at present limited; but 
this limit he may at some future period be able to overpass, and we 

. * It is identical in constitution with caramel (p. 114)~the uncrystallizable sugar of syrups. 
For 

Vinegar. Caramel. 

(C4 H3 O3 X 3) = C12 H9 O9. 



128 POWER OF THE CHEMIST OVER MATTER. 

know not how far. The discovery of a new agent, or of a new mode 
of treatment, may enable him to accomplish what he has not as yet the 
means or the skill to perform. 

2°. He has it in his power to form, actually to produce, some of the 
organic or organized substances which occur in living plants. He can 
forrn gum, and grape sugar, in any quantity. Tlius far he can imitate 
and take the place of the living principle itself. 

Numerous other cases are known, in which he displays a similar 
power. By the action of nitric acid upon starch or sugar, [see Lecture 
in., p. 47,] he can form oxalic acid, which, as has already been shown, 
occurs very largely in the vegetable kingdom. By the action of heat 
upon citric acid, he can decompose it and produce an acid which is 
met with in the "Wolfsbane (Aconitum napellus), and hence is called 
aconitic acid.* Also by the action of sulphuric acid he can change 
salicine and phlorizine — substances extracted respectively from the bark 
of the willow and from that of the root of the apple tree — into a resinous 
matter and grape sugar. So, of the compounds which are found in the 
solids and fluids of animal bodies, there are some which he has also 
succeeded in forming by the aid of his chemical art. 

Elated by such achievements, some chemists appear willing to hope 
that all nature is to be subjected to their dominion, and that they may 
hereafter be able to rival the living principle in all its operations. It is 
true that what we now know, and can accomplish, are but the begin- 
nings of what we may fairly expect hereafter to effect- But it is of con- 
sequence to bear in mind the true position in which we now stand, and 
the true direction in which all we at present know seems to indicate that 
our future advances in knowledge, and in control over nature, are likely 
to proceed. And this leads me to observe — 

3°. That our dominion is at present limited solely to transforming 
and decomposing. We can transform woody fibre into gum or sugar— 
we cannot form either gum or sugar by the direct union of their elements. 
We can resolve salicine by the acid of sulphuric acid into resin and 
grape sugar ; but we cannot cause the elements of which they consist to 
unite together in our hands, so as to form any one of the three. We 
cannot even cause the resin and the sugar to re-unite and rebuild the sali- 
cine from which they were derived. 

So we can by heat drive off the elements of water from the citric and 
cause tiie aconitic acid to appear ; but we cannot persuade the unwilling 
compounds, when thus separated, to return to their former condition of 
citric acid ; and, if we could, we should still be as far removed from the 
power of commanding or compelling the direct union of carbon, hydro- 
gen, and oxygen, in such proportions, and in such a way, as to build up 
either of the two acids in question. 

Again, we can actually form oxalic acid by the action of nitric acid 

' These two acids differ from each other only i y the elements of an atom of water. Thus 
Citric Acid . . = C i •• 04 
Aconitic Acid . = C4 Hj O3 

Difference , . =^ Hi O or HO, one of water. 
It Is easy to see, therefore, how, by the evolution of the elements of an atom of water, the • 
one acid may be changed into the other. The scientific reader will excuse me (if on the 
grounds of simplicity alone) for representing, both here and in the text, the citric acid by 
C H2 O4, instead of by C12 H3 On -^ 3H0', which Liebig and his pupils prefer. 



TKUE PROSPECTS OF CHEMICAL SCIENCE. 129 

upon Starch, or wood, or sugar, or any other of a great variety of vegeta- 
ble substances — but we cannot prepare it by the direct union of its ele- 
ments. We can only as yet procure it from substances which have 
already been organized — which have been themselves produced by the 
agency of the living principle. 

The same remarks apply with slight alteration to those substances of 
animal origin to which I have above alluded as being within the power 
of the chemist to produce at will. There is hardly an exception to the 
rule, that in producing organic substances, as they are called, the chem- 
ist must employ other organic substances which are as yet beyond his 
art — which, so far as we know, can only be formed under the direction 
of the living principle. Thus the sum of the chemist's power in imita- 
ting organic nature consists, at present, in his ability 

l'^. To transform one substance found only in the organic kingdom 
into some other substances, produced more or less abundantly in the 
same kingdom of nature. This power he exercises when lie converts 
starch into sugar, or fibrin into albumen or casein. 

2°. To resolve a more complex or compound substance into two or 
more which are less so, and of which less complex substances some may 
be known to occur in vegetable or animal bodies. 

3°. To decompose organic compounds by means of his chemical agents, 
and as the result of such decompositions to arrive at one or more com- 
pounds, such as are formed under the direction of the living principle. 

In no one case can he form the substances of ivhich animals and plants 
cliiejly consist, out of those on which animals and plants chiefly live. 

But this is the common and every-day result of the agency of the liv- 
ing principle. Is there as yet, then, any hope that the chemical labo- 
ratory shall supersede the vascular system of animals and plants ; or 
that the skill of the chemist who guides the operations within it, shall 
ever rival that of the principle of life, which presides over the chemical 
changes that take place in animal and vegetable bodies ? 

The true place, therefore, of human skill — the true prospects of chem- 
ical science — are pointed out by these considerations. No science has 
accumulated so many and such various treasures as chemistry has done 
•during the last 20 years — none is at present so widely extending the 
JDounds of our knowledge at this moment as the branch of organic chem- 
istry — nien may therefore be excused for entertaining more sanguine 
expectations from the progress of a favourite science than sober reason- 
ing would warrant. Yet it is of importance, I think, and especially in 
a moral point of view, that amid all our ardour, we should entertain 
clear and just notions of the kind and extent of knowledge to which we 
are Hkely to attain, and — as knowledge in chemistry is really power 
over matter — to what extent this power is likely ever to be carried. 

At present, if we judge from our actual knowledge, and not from our 
hopes — there is no prospect of our ever being able to imitate or rival 
living nature in actually compounding from^heir elements her nume- 
rous and varied productions. That we may clearly understand, and be 
able to explain many of her operations, and even to aid her in effecting 
ihem, is no way inconsistent with an inability to imitate her by the re- 
sources of art. This will, I trust, appear more distinctly in the subse- 
quent lecture. 



LECTURE VII. 

Chemical changes by which the substances of which plants chiefly consist are formed from 
those on which they live.— Changes during germination — during the growth of the plant — 
during the ripening of fruit.— Autumnal changes. 

Having thus cotisidered the nature and chemical constitution of those 
substances which constitute by far the largest part of the solids and 
fluids of living vegetables, we are now prepared for the further question 
— hy what chemical changes these substances of which ijlants consist, are 
formed out of those on which they live ? 

The growth of a plant from the germination of the seed in spring till 
the fall of the leaf in autumn, or the return of the succeeding spring- 
time, may in perennial plants be divided into four periods — during which 
they either live on different food, or expend their main strength in the 
production of different substances. These periods may be distinguished 
as follows : — 

1°. The period of germination — from the sprouting of the seed to the 
formation of the perfect leaf and root. 

2°. From the expansion of the first true leaves to the period of flow- 
ering. 

3°. From the opening of the flower to the ripening of the fruit and 
seed. 

4°. From the ripening of the seed or fruit, till the fall of the leaf and 
the subsequent return of spring. On the ripening of the fruit the func- 
tions of annual plants are in general discharged, and they die; but per- 
ennial plants have still important duties to perform in order to prepare 
them for the growth of the following spring. 

The explanation of the chemical changes to which our attention is to 
be directed will be more clear, and perhaps more simjjle, if we consider 
them in relation to these several periods of growth. 

§ 1. Chemical changes tvhich take place during germination and during 
the develojjment of the first leaves and roots. 

The general nature of the chemical changes which take place during | 
germination is simple and easy to be comprehended. "i 

Let us first consider shortly the phenomena which have been observed i 
to accompany germination, and the circumstances which are most fa- 
vourable to its rapid and healthy progress. 

1°. Before a seed will begin to sprout, it must be ])laced for a time in j 
a sufficiently moisl situation. We have already seen how numerous 
and important are the functions which water performs in reference to 
vegetable life (Lecture IL, p. 36,) in every stage of a plant's growth. 
In the seed no circulation can take place — no motion among the parti- 
cles of matter — until water has beer largely imbibed ; nor can the food 
be conveyed through the growing vessels, unless a constant supply of 
fluid be afforded to the seed and its infant roots. 

2°. A certain degree of warmth — a slight elevation of temperature- 
is also favourable, and in most cases necessary, to germination. 



EFFECT OF AIR AND LIGHT ON GERMINATION. 131 

The degree of warmth which is required in order that seeds may be- 
gin to grow, varies with the nature of the seed itself. In Northern Si- 
beria and other icy countries, plants are observed to spring up at a tem- 
perature but slightly raised above the freezing point (32° F.,) but it is 
familiar to every practical agriculturist, that the seeds he yearly con- 
signs to the soil require to be protected from the inclemency of the 
weather, and sprout most quickly when they are stimulated by the 
warmth of approaching spring, or by the heat of a summer's sun. 

The same fact is familiarly shown in the malting of barley, where 
large heaps of grain are moistened in a warm atmosphere. When ger- 
mination commences, the grain heats spontaneously, and the growth 
increases in rapidity as the heap of corn attains a higher temperature. 
It thus appears that some portion of that heat which the growth of the 
germ and radicles requires, is provided by natural processes in the grain 
itself; in some such way as, in the bodies of animals, a constant supply 
of heat is kept up by the vital processes — by which supply the cooling 
etfect of the surrounding air is continually counteracted. 

We have seen in the preceding lecture, that the transformations of 
which starch and gum are susceptible, take place with greater certainty 
and rapidity under the influence of an elevated temperature. It will 
presently appear that such transformations are also attected during ger- 
mination ; there is reason, therefore, to believe that the external warmth 
which is required in order that germination may begin, as well as the 
internal heat naturally developed as germination advances, are both 
employed in effecting these transformations. And, as the young sprout 
shoots more rapidly under the influence of a tropical sun, it is probable 
that those natural agencies in general, by which such chemical transfor- 
mations are most rapidly promoted, are also those by which the pro- 
gress of vegetation is in the greatest degree hastened and promoted. 

3°. It has been observed that seeds refuse to germinate if they are en- 
tirely excluded from the air. Hence seeds which are buried beneath 
such a depth of soil that the atmospheric air cannot reach them, will 
remain long unchanged, evincing no signs of life — and yet, when turned 
up or brought near the surface, will speedily begin to sprout. Thus in 
trenching the land, or in digging deep ditches and drains, the farmer is 
often surprised to find the earth, thrown up from a depth of many feet, 
become covered with young plants, of species long extirpated from or 
but rarely seen in his cultivated fields. 

4°. Yet light is, generally speaking, prejudicial to germination. 
Hence the necessity of covering the seed, when sown in our gardens and 
corn fields, and yet of not so far burying it that the air shall be excluded. 
In the usual method of sowing broad-cast, much of the grain, even after 
harrowing, remains uncovered : and the prejudicial influence of light in 
preventing the healthful germination of such seeds is no doubt one rea- 
son why, by the method of dibbling, fewer seeds are observed to fail, and 
an equal return of corn is obtained from a much smaller expenditure of 
seed. 

The reason why light is prejudicial to germination, as well as why 
the presence of atmospheric air is necessary, will appear from the fol- 
lowing observation : — 

5°. When seeds are made to germinate in a limited portion of atmos- 



132 SEEDS SPROUT ONLY IN THE PRESENCE OF OXYGEN. 

pheric air, the bulk of the air undergoes no material alteration, but on 
examination its oxygen is found to have diminished, and carbonic acid 
to have taken its place. Therefore, during germination, seeds absorb 
oxygen gas and give off carbonic acid. 

Hence it is easy to understand why the presence of air is necessary 
to germination, and why seeds refuse to sprout in hydrogen, nitrogen, 
or carbonic acid gases. They cannot sprout unless oxygen be within 
Vieir reach. 

We have seen also in a previous lecture that the leaves of plants in 
the sunshine give off" oxygen gas and absorb carbonic acid, — while in 
the dark the reverse takes place. So it is with seeds which have begun 
to germinate- When exposed to the light they give off" oxygen instead 
of carbonic acid, and thus the natural process is reversed. But it is ne- 
cessary to the growth of the young germ, that oxygen should be absorb- 
ed, and carbonic acid given of — and as this can take place to the requir- 
ed extent only in the dark, the cause of the prejudicial action of light is 
sufficiently apparent as well as the propriety of covering the seed with a 
thin layer of soil. 

6°. During germination, vinegar (acetic acid) and diastase are pro- 
duced. Thai such is the case in regard to the latter substance, has been 
proved in the previous lecture, (p. 118.) That acetic acid is formed is 
shown by causing seeds to germinate in powdered chalk or carbonate of 
lime, when after a time acetate of lime* may be washed out from the 
chalk (Braconnot) in which they have been made to grow. The acid 
contained in this acetate must have been formed in the seed, and after- 
wards excreted or thrown out into the soil. 

7°. When the germ has shot out from the seed and attained to a sen- 
sible lengtii, it is found to be possessed of a sweet taste. This taste is 
owing to the presence oi grape sugar in the sap which has already be- 
gun to circulate through its vessels. 

It has not been clearly ascertained whether the vinegar or the dias- 
tase is first produced when germination commences, but there seems 
little doubt that the grape sugar is formed subsequently to the appear- 
ance of both. 

8^. The young shoot which rises upwards from the seed consists of 
a mass of vessels, which gradually increase in length, and after a short 
time expand into the first true leaves. The vessels of this first shoot do 
not consist of unmixed woody fibre. It is even said that no true wood 
is formed till the first true leaves are developed. — [Lind ley's Theory of 
Horticulture.] The vessels of the young sprout, therefore, and of the 
early radicles, probably consist of the cellular fibre of Payen. They 
are uncjuestionably formed of a substance which is in a state of transition 
between starch or sugar and woody fibre, and which has a constitution 
analogousf to that of both. 

Having thus glanced at the phenomena which attend upon germina- 
tion, let us now consider the chemical changes by which these phenom- 
ena are accompanied. 

1°. The seed absorbs oxygen and gives off* carbonic acid. We have 

* Acetate of lime is a compound of acetic acid (vinegar) and lime, and may be prepared by 
dissolving chalk in vinegar. It is very soluble in water. 
t By analogous I mean which may be represented by carbon and water. 



HOW AND WHY VINEGAR IS FORMED. 133 

already seen that the starch of the seed (C.^ H^o O,o) may be repre- 
sented by carbon and water,— by 12C + lOHO. Now it appears that 
in contact with the oxygen of the atmosphere, a portion of the starch is 
actually separated into carbon and water, the carbon at the moment of sepa- 
ration uniting with the oxygen, and forming carbonic acid (COo). This 
acid is given off; into the soil in the form of gas, and thence partially es- 
capes into the air; but for what immediate purpose it is evolved, or how 
Its formation is connected with the further development of the germ, has 
not hitherto been explained. 

2°. The formation of acetic acid (vinegar) from the starch of the 
grain is also easy to comprehend. For, as we have already seen, 
Starch . . . =C,2 H „ 0,o 
3 of Vinegar ..^CiaHg O9 

Difference = H, O, ; or the elements of 

an atom of water, 1 herefore, in this early stage of the growth of the 
germ a portion of the starch is deprived of the elements of an atom of 
water, and at the same time transformed into vinegar. 

Why is this vinegar formed 1 It is almost as difficult to answer this 
question as to say why carbonic acid is evolved from the seed, though 
both undoubtedly serve wise and useful ends. 

It has been explained in the preceding lecture how the action of dilute 
acids gradually changes starch into cane sugar, and the latter into grape 
sugar. While it remains in the sap of the sprouting seed, the vine<^ar 
may aid the diastase in transforming the insoluble starch into soluble 
food for the plant, and may be an instrument in securing the conversion 
of the cane sugar, which is the first formed, into grape sugar,— since 
cane sugar cannot long exist in the presence of an acid. 

After the acetic acid is rejected by the plant, it may act as a solvent 
on the lime and other earthy matters contained in the soil. Liebig sup- 
poses the especial function of this acid — the reason why it is formed in 
the germ and excreted into the soil — to be, to dissolve the lime, «fec., which 
the soil contains, and to return into the pores of the roots, bearing in so- 
lution the earthy substances which the plant requires for its healthy 
growth. This is by no means an unlikely function. It is only conjec- 
tural, however, and since the experiments of Braconnot have shown that 
acetate of lime, even in small quantity, may be injurious to vegetation, 
it becomes more doubtful how far theVormation of this compound in the 
soil, and the subsequent conveyance of it into the circulation of the plant, 
can be regarded as the special purpose for which acetic acid is so gene- 
rally produced during germination. 

3°. The early sap of the young shoot is sweet ; it contains grape su- 
gar. This sugar is also derived from the starch of the seed. Being 
rendered soluble by the diastase formed at the base of the germ, the 
starch is gradually converted into grape sugar as it ascends. The rela- 
tion between these two compounds has been already pointed out. 

Starch ^CisHjoPio 

Grape Sugar . . . = C12 H12 O12 

Difference . . . . = Hg O2 ; or the ele- 

ments of two atoms of water. The water which is imbibed by the seed 
12 "^ 



134 HOW THE SUGAR IS FORMED IN THE SPROUT. 

from the soil, forms an abundant source from which the whole of the 
starch, rendered soluble by the diastase, caa be supplied with the ele- 
ments of the two atoms of water which are necessary to its subsequent 
conversion into grape sugar 

4°. The diastase is formed when the seed begins to sprout, at the ex- 
pense of the gluten or vegetable albumen of the seed, but as its true 
constitution is not yet known, we cannot explain the exact chemical 
changes by which its production is eifected. 

5°. When the true leaf becomes expanded, true wood first appears 
in sensible quantity. By what action of the sun's rays upon the leaf 
the sugar already in solution in the sap is converted into woody fibre, 
we cannot explain. The conversion itself is in appearance simple 
enough, since 

Grape Sugar . . . = C^g H^g ^\2i ^^^^ 
Woody Fibre . . . =Ci2 ^3 O3 



Difference . . . . = H4 O4 ; or the former 

must part with the elements of four atoms of water only, to be prepared 
for its change into the latter. But the true nature of the molecular* 
change by which this transformation is brought about, as well as the 
causes which lead to it and the immediate instruments by which it is J 
effected, are all still mysterious. 

§2. Of the chemical changes ivhick take place from the formation of the 
true leaf to the expansion of the flower. 

When the true leaf is formed the plant has entered upon a new stage 
of its existence. Up to this time it is nourished almost solely by the 
food contained in the seed, — it henceforth derives its sustenance from the 
air and from the soil. The apparent mode of growth is the same, the 
stem shoots upwards, the roots descend, and they consist essentially of 
the same chemical substances, but they are no longer formed at the ex- 
pense of the starch of the seed, and the chemical changes of which they 
are the result are entirely different. 

1°. The leaf absorbs carbonic acid in the sunshine, and gives off ox- 
ygen in equal bulk.f It is in the light of the sun that plants increase in 
size — their growth, therefore, is intimately connected with this absorp- 
tion of carbonic acid. 

If carbonic acid be absorbed by the leaf and the whole of its oxygen 
given off again, t carbon alone is added to the plant by this function of 
the leaf. But it is added in the [)resence of the water of the sap, and 
thus is enabled by uniting with it to form, as it mo.y he directed, or as . 
may be necessary, any one of those numerous compounds which may ' 

* All bodies are supposed to consist of particles or moZ^CJ/Zes of exceeding minuteness, 
and all chemical changes which take place in the same mass of matter are supposed to be 
owing to the different ways in which these I'artlcles arrange themselves. We may form a 
remote idea of the way in which different positions of the same particles may produce dif- 
ferent substances, by considering how different fiuures in Mosaic may be produced by dif- 
ferent arrangements of the same number of equal and similar fragments of various colours. 

t Such 'insensibly the result of experiment. How far this result can be considered as uni- 
versally true, will be examined hereafter 

X It will be recollected tliat carbonic acid contains its own bulk of oxygen gas : if, therefore, 
the leafgiveoff the same bulk of oxygen as it absorbs of carbonic acid, the result must be as 
stated in tlie text. 



HOW PLANTS ARE NOURISHED BY CARBONIC ACID ? 135 

be represented by carbon and water, (p. Ill,) and of which, as we have 
seen, the solid parts of plants are chiefly made up. 

There are two waj'S in which we may suppose the oxygen given off 
by the leaf to be set free, and the starch, sugar, and gum, to be subse- 
quently formed. 

A. The action of light on the leaf of the plant may directly decompose 
the carbonic acid after it has been absorbed, and cause the oxyen to sep- 
arate from the carbon, and escape into the air ; — while at the same in- 
stant the carbon thus set free, may unite with the water of the sap in 
different proportions, so as to produce either sugar, gum, or starch. 
Suppose 12 atoms of carbonic acid (12 CO^) to be thus decomposed, and 
their carbon to unite with 10 of water (10 HO), we should have 
from 12 of Carbonic Acid . = 0^2 

which united to 10 of Water . . . =: Hio Oio 



would give 1 of Gum or of Cane Sugar = C,2 ^lo ^lo 
while 24 of oxygen would be given off, the whole of which would have 
been derived from the carbonic acid absorbed by the plant. 

B. Or the action of the sun's rays may be directed, in the leaf, to the 
decomposition-, not of carbonic acid, but of the water oi i\\e sap. The oxy- 
gen of the water may be separated from the hydrogen, while at the same 
instant the latter element (hydrogen) may unite with the carbonic acid 
to produce the sugar or starch. The result here is the same as before, 
but the mode in which it is brought about is very differently represented, 
and appears much more complicated. Thus, suppose 24 of water 
(24 HO) to be decomposed, and to give off their oxygen into the air, 24 of 
oxygen would be evolved as in the former case, the whole o^ which 'would 
he derived from the decomposition ofivater, while there would remain 
24 of Hydrogen . . = H 4 

Let this act on 12 of Carbonic Acid = C^g ^24 



and we have as the result C^g H24 O24 ; 

Starch, «&c. Water. 

or C,2 Hio Oio + 14HO. 

According to this mode of representing the cliemical changes, water is 
first decomposed and its oxygen evolved, then its hydrogen again com- 
bines with the carbon and oxygen of the carbonic acid, and forming two 
products — water and sugar or starch. This view is not only more com- 
plicated, but it supposes the same action of light to be — continually, at 
the same time, and in the same circumstances — both decomposing wa- 
ter and re-forming it from its elements. While, therefore, there can be 
no doubt, for other reasons not necessary to be stated in this place, tliat 
the light of the sun really does decompose water in the leaves of plants, 
and more in some than in others — yet it appears probable that the oxygen 
evolved by the leaf is derived in a great measure from the carbonic acid 
which is absorbed; and that the principal part of the solid substance of 
living vegetables, in so far at least as it is derived from the air, is pro- 
duced by the union of the carbon of this acid with the elements of the 
water in the sap.* 

* I ought not to pass unnoticed the opinion of Persoz (Chemie Molecidaire'), that the 
starch, gum, <fec., of plants are formed by the union of carbonic oxide (CO) with the neces- 



136 IS CARBONIC ACID ABSORBED FROM THE SOIL ? 

We have seen reason to conclude (p. 63) ihat, while plants derive 
much of their sustenance from the air, they are also fed more or less 
abundantly by the soil in which they grow. From this soil they ob- 
tain through their roots the carbonic acid which is continually given off 
by the decaying vegetable matter it contains. This carbonic acid will 
ascend to the leaf, and will there undergo decomposition along with that 
which is absorbed by the leaf itself. At least we know of no function 
of the root or stem by which the carbonic acid derived from the soil can 
be decomposed and deprived of its oxygen before it reaches the leaf. 

It is distinctly stated, indeed, by Sprengel, [see above, p. 92,] that 
when the roots of a plant are in the presence of carbonic acid, the oxy- 
gen given off by the leaf is greater in bulk than the carbonic acid ab- 
sorbed. But there is one observation in connection with this point which 
it seems to me of importance to make. The leaves supply carbon to 
the plant only in the form of carbonic acid, and they give off a bulk of ^ 
oxygen gas not exceeding that of the acid taken in, [see note, below.] 
But if the carbon derived from the soil be also absorbed in the form of 
carbonic acid, and if the oxygen contained in this portion of acid is also 
given off by the leaf — either the cpiantity drawn from the soil must be 
small, compared with that inhaled from the air, or the oxygen given off 
by the leaf must, in the ordinary course of vegetation, be sensibly great- 
er than the bulk of the carbonic acid which it absorbs. 

We are too little famihar with the chemical functions of the several 
parts of plants to be able to pronounce a decided opinion on this point; 
but it appears evident that one or other of the three following conditions 
must obtain : — 

{a). Either in the general vegetation of the globe the bulk of the oxy- 
gen gas given off by the leaf during the day must always be considera- 
bly greater than that of the carbonic acid absorbed by it ; or 

(&). The root or stem must have the power of decomposing carbonic 
acid and of separating and setting free its oxygen ; or 

(c). The plant can derive no considerable portion of its carbon from 
the soil, in the form of carbonic acid. 

If the experiments hitherto made by the vegetable physiologists be 
considered of so decisive a character as to warrant us in rejecting the 
two former conditions, the third becomes also untenable. 

sary proportions of oxygen and hydrogen derived from the water of the sap. This opinion 
implies that, in the leaf, carbonic acid (CO2 ) is decomposed into carbonic oxide and oxy- 
gen (CO + O), and that water likewise is decomposed, — the oxygen produced by both de- 
compositions being given off either into the air by the leaves, or into the soil by the roots. 
The production of grape sugar, therefore, according to this hypothesis, would be thus repre- 
IBCnted : — There are retained, and given off. 

From 12 of Carbonic Acid = I2CO2 - - - C12 O12 O12 

From 12 of Water- - - = 12HO - ■ - H12 O12 



C12H12O12 O24 

grape sugar 

Of the 24 of oxygen thus given off, the opinion of Persoz is, that only one-half is evolved 
by the leaf, — and the principal fact on which his opinion rests is that observed by De Saus- 
sure, that plants of Vinca minor gave off by their leaves, in his experiments, only two-thirds 
of the oxygen contained in the carbonic acid they absorbed. This result has led Berzelius 
also to conjecture that the leaves of plants do not retain merely the carbon of the carbonic 
acid, but some compound of carbon with oxygen, containing much less of this element than 
the carbonic acid does{Traite de Chemie, V , p. 69). The principal objection to this view, 
however, is the quantity of oxygen it supposes to be rejected by the root. The experiments 
on which it is founded require confirmation and extension. 



HOW SUGAR IS TRANSFORMED INtO STARCft. 137 

3°. Without dwelling at present on this point, the fibove considera- 
tions may be regarded as giving additional strength or probability to the 
conclusions v/e formerly arrived at (p. 63) from other premises — that 
the roots, besides carbonic acid, absorb certain other soluble organic 
compounds, which are always present in the Soil in greater or less 
quantity, and that the plant appropriates and converts these into its own 
substance. Some of these organic compounds may readily, and by ap- 
parently simple changes, be transformed into the starch and woody fibre 
of ihe living vegetable. The illustration of this fact will be reserved 
until, in the second part of these lectures, I come to treat of the vegeta- 
ble portion of soils, and of the chemical nature and constitution of the 
organic compounds of which it consists, or to which it is capable of giv- 
ing rise. 

4°. The chemical changes above explaitied (a), show how, from 
carbonic acid and the elements of water, substances possessed of the 
elementary constitution of sugar and gum may, by the natural processes 
of vegetable life, obtain the elements of which they consist, and in the 
requisite proportions. They throw no light, however, upon the me- 
chanism by which these elements are constrained, as it were, to assume 
first the form of gum or sugar, or soluble starch, and afterwards., in 
another part of the plant, of insoluble starch and woody fibre. 

It is known that the sap deposits starch and woody fibre in the stem,; 
only in its descent from the leaf, — and it is, therefore, inferred that the 
action of light upon the sap, as it passes through the green parts, iS ne- 
cessary to dispose the elements to arrange themselves in the form of 
vascular fibre or lignin. And as, by the agency of nitric acid, starch 
appears to be convertible into woody fibre (p. 126), it is not unlikely 
that the soluble substances, containing nitrogen, which are present in 
the sap may — as diastase does upon starch — exercise an agency in trans- 
forming the soluble sugar, gum, &:c., of the sap into the insoluble starch 
and woody fibre of the seed and the stem. We are here, however, upon 
uncertain ground, and I refrain from advancing any further conjectures. 

Two great steps we have now made. We have seen how the germ 
lives and grows at the expense of the food stored up in the seed — and 
how, when it has obtained roots and leaves, the plant is enabled to ex- 
tract from the air and from the soil such materials as, in kind and quan- 
tity, are fitted to build up its several parts during its future growth. 
That considerable obscurity still rests on the details of what takes place 
in the interior of the plant, does not detract from the value of what we 
have already been able to ascertain. 

§ 3. On the production of oxalic acid in the leaves and stems of plants. 
In the preceding section we have studied the origin of those sub- 
stances only which form the chief bulk of the products of vegetation, 
and which are characterized by a chemical constitution of such a kind 
as enables them to be represented by carbon and water. But during 
the stage of vegetable growth we are now considering, other compounds 
totally different in their nature are also produced, and in some plants in 
sufficient quantity to be deserving of a separate consideration. Such is 
the case "with oxalic acid. 

The circumstances under which this acid occurs in nature have al- 



138 PRODUCTION OF OXALIC ACID IN PLANTS. 

ready been detailed. It is found in small quantities in many plants. 
The potash in forest trees is supposed to be in combination with oxalic 
acid, while in the lichens oxalate of Lime serves a purpose similar to that 
performed by. the woody fibre of the more perfect plant ; it forms the 
skeleton by which the vegetable structure is supported, and through 
which its vascular system is diffused. 

The production of this acid in the living plant is readily understood 
when its chemical constitution (Cg O3) is compared with that of car- 
bonic acid (CO2). For 

2 of Carbonic Acid = C2 O4 
1 of Oxalic Acid = C2 O3 



Difference . . . O^ 

That is to say, 2 of carbonic acid are transformed into 1 of oxalic acid 
by the loss of 1 equivalent of oxygen — or generally, carbonic acid by the 
loss of one-fourth of its oxygen may be converted into oxalic acid. 

But the leaf absorbs carbonic acid and gives off" oxygen. In the lichens, 
therefore, which contain so much oxalic acid, a large portion of the car- 
bonic acid absorbed is, by the action of light, deprived of only one-fourth 
of its oxygen, and is thus changed into oxalic acid. The same is true to 
a smaller extent of the sorrel leaves and stems, which owe their sour- 
ness to the presence of oxalic acid — of the leaves and stems of rhubarb 
also — in a still smaller degree of the beech and other large trees, in 
which much potash, and probably also of marine plants, in which 
much soda is found to exist. It must be owing to the peculiar structure 
of the leaves of each genus or natural order of plants, that the same ac- 
tion of the same light decomposes the carbonic acid in different degrees 
— evolving in some a less proportion of its oxygen, and causing in such 
plants the formation of a larger quantity of oxalic acid. 

The fact of the production of this oxalic acid, to a very considerable 
amount in many plants, is a further proof of the uncertainty of those 
experiments from which physiologists have concluded that the leaves 
of plants emit a bulk, of oxygen sensibly equal to that of the carbonic 
acid absorbed.* 

I have referred the production of more or less oxalic acid in different 
plants to the special structure of each, and this must be true, where, in 
the same circumstances, different results of this kind are observed to 
take place — as where sorrels and sweet clovers grow side by side. Yet 
the influence of light of different degrees of intensity on the same plant, 
is beautifully shown by the leaves of the Sempervivum arboreum, of the 
Portulacaria afra, and other plants which are sour in the inorning, tasteless 

* Were we permitted, in the absence of decisive experiments, to state as true what theo- 
retical considerations plainly indicate, we should say— 

1°. That plants containing much oxalic or other similar acids, and not deriving much car- 
bonic acid from the soil, must give ofFfi'om their leaves a bulk of oxygen less than that of the 
carbonic acid absorbed. 

2°. That plants containing no sensible quantity of such acids, nor fed by carbonic acid 
from the soil, may evolve oxygen sensibly equal in bulk to the carbonic acid absorbed. 

3°. That if littie of these acids be present, and much carbonic acid be absorbed from the 
soil, the volume of oxygen "ivenoff by the green parts of the plant must be sensibly ^rea/er 
than that of the carbonic acid they absorb. 

4°. That the leaves of the pines and other trees containing much turpentine — in which 
hydrogen is in excess— must at all times give off oxygen in greater bulk than the, carbonic 
acid they absorb. They must decompose water as well as carbonic acid, and evolve the 
oxygen of both. 



ACTION OF THE FLOWER LEAVES ON THE AIR. 139 

2/1 the middle of the day, and hitler in the evening. — [Sprenge , Chemie, 
II., p. 321.] During the night the oxygen hae-accumulated in these plants 
and formed acids containing OKygen in excess (p. 127.) As the day ad- 
vances this oxygen is given off; under the influenceof light the acids are 
decomposed, and the sourness disappears. 

In tlie juices of plants before the period of flowering, other acids are 
met with besides the oxalic acid, though in much smaller quantity. As 
the most important of these, however, occur more abundantly in fruits, 
we shall consider the theory of their formation in the following section. 

§ 4. Of the chemical changes which take place between the opening of the 
flower and the ripening of the fruit or seed* 

The opening of the flower is the first and most striking step taken by 
the plant towards the production of the seed by which its species is to be 
perpetuated. That at this period anew series of chemical changes com- 
mences in the plant is obvious from the following facts : — 

1°. That the flower leaves absorb oxygen and emit carbonic acid both 
by day* and by night (p. 95.) 

2°. That they also occasionally emit pure nitrogen gas. 

3°. That the juice of the maple ceases to be sweet when the flowers 
are matured (Liebig,) and that, in the sugar cane and beetroot, the sugar 
• becomes less abundant when the plant has begun to blossom. 

These facts sufficiently indicate the commencement of new changes 
in the interior of plants at this period of their growth. That such changes 
go on until the ripening of the seed is also evident from these further ob- 
servations : — 

1°. That the husk of the future seed, as in the corn-bearing grasses 
(wheat, oats, &c.,) is filled at first with a milky liquid, which becomes 
gradually sweeter and more dense, and finally consolidates into a mix- 
ture of starch and gluten, such as is presented by the flour of different 
species <if corn. 

2°. That the fruit in which the seeds of many plants is enveloped is 
at first tasteless, afterwards more or less sour, and finally sweet. In a 
few fruits only, as in the lime, the lemon, and the tamarind, does a suf- 
ficient quantity of acid remain to be sensible to the taste, when the seed 
has become perfectly ripe. The acid and cellular fibre both diminish 
while the sugar increases. 

3°. That fruits, while green, act uix)n the air like the green leaves and 
twigs — but that, as they approach maturity, they also absorb or retain 
oxygen gas (De Saussure.) The same absorption of oxygen takes place 
when unripe fruits are plucked and left to ripen in the air (Berard.) 
After a time the latter also emit carbonic acid. 

I. — FORMATION OF THE SEED. 

In the case of wheat, barley, or other plants, which yield farinaceous 
seeds, we have seen that previous to flowering the chief energy of the 
living plant is expended in the production of the woody fibre of which 
its stem and growing branches mainly consist; and we have also been 
able to understand, in some degree, how this woody fibre is produced 
from ihe ordinary food of the plant. When the flower expands, how- 

* By day the absorpli<tn is the greater, but the bulk of the oxygen taken in is always 
greater than that of the carbonic acid given off. 



140 FORMATION Or THE SEED, AND RIPENING OF THE FRUIT. 

ever, the plant has in general, and especially if an annual plant, reached 
nearly to maturity, and woody fibre is little required. The most im- 
portant of its remaining functions is the production of the starch and glu- 
ten of the seed, and of the substances which form the husk by which the 
seed is enveloped. 

In the first stages of the plant's growth, the starch of the seed is 
transformed into gum and sugar, and subsequently, when the leaves are 
expanded, into woody fibre. In the last stages of its existence, when il 
is producing the seed, the sugar of the sweet and milky sap is gradually 
transformed into starch — that is to say, a process exactly the converse 
of the former takes place. 

We are able, in some measure, to explain the mode and agency by 
which the former transformation is effected — the latter, however, is still 
inexplicable. We can ourselves, by the agency of diastase, transform 
starch into sugar ; and, therefore, can readily believe such transforma- 
tions to be effected in the young plant ; — but we as yet know no method 
of re-converting sugar into starch ; and, therefore, we can only hazard 
conjectures as to the way in which this change is brought about in the 
interior of the plant during the formation of the seed. 

It is said that nitrogen is given off by the flower leaf. We know that 
this element is present in the colouring matter of the petal, and that it is a 
necessary'' constituent of the albumen and gluten, which are always as- 
sociated with the starch of the seed. It is plain, then, that the nitrogene- 
ous substances [substances containing nitrogen,] contained in the sap at 
all periods of the plant's growth, are carried up in great quantity to the 
flower and seed vessel. These substances are supposed to be concerned as 
immediate agents in effecting the transformations which there take place. 
More than this, however, we cannot as yet venture even to conjecture. 

II. RIPENING OF THE FRUIT. 

In these plants, again, which invest their seed with a pulpy fruit — in 
the grape, the lemon, the apple, the plum, &c. — other changes take 
place, at this period, of a more intelligible kind, and other substances are 
formed, on the production of which less obscurity rests. At one stage of 
their growth, these fruits, as has been already stated, are tasteless — in the 
next, they are sour — in the third, they are more or less entirely sweet. 

I. In the tasteless state they consist of little more than the substance 
of the leaf— of vascular, or woody fibre, filled with a tasteless sap, and 
tinged with the colouring matter of the green parts of the plant. For a 
time, this young fruit appears to perform in reference to the atmosphere 
the usual functions of the leaf— it absorbs carbonic acid and gives off' oxy- 
gen, and thus extracts from the air a portion of the food by which its growth 
is promoted, and its size gradually increased. 

II. But after a time this fruit becomes sour to the taste, and its 
acidity gradually increases — while at the same time it is observed to 
give off a less comparative bulk of oxygen than before. Let us consi- 
der shortly the theory of the production of the more abundant vegetable 
acids contained in fruits. 

1°. The tartaric acid which occurs in the grape is represented by 
C4 H2 O5 (p. 124). 

There are two ways in which we may suppose this acid to be formed 



FORMATION OF TARTARIC, MALIC, AND CITRIC ACIDS. 141 

in the fruit — either directly from the elements of carhonic acid and wa- 
ter witli the evolution of oxygen gas — or from the gum and sugar al- 
ready present in the sap aided by the absorption of oxygen from the at- 
mosphere. Thus 

A. 4 of Carbonic Acid = 0403 
2 of Water . . = Ho O2 

Sum . . = C4 H2 Oio or 04^82 O5 -f 50. 
That is, one equivalent of tartaric acid may be formed from 4 of carbon- 
ic acid absorbed by the leaf or fruit, and 2 of the water of the sap, while 
5 of oxygen are at the same time given off by the leaf Or, 

B. If Grape Sugar be C,2 Hjg O12 

I of Grape Sugar = C4 H3 O3 
3 of Oxygen . . = O3 

Tartaric Acid. Water. 

Sum . . = C4 H3 Oe or C4 H2 O5 + HO. 

That is, by the absorption from the air of a quantity of oxygen equal to 
that which it already contains, grape sugar may be converted into tar- 
taric acid and water. 

In the sorrels and other sour-leaved plants, which contain tartaric acid 
in their general sap, the acid may be formed by either of the processes 
above explained. In the sunshine their green parts absorb carbonic 
acid and evolve oxygen. If any of these green parts give off only | of 
the oxygen contained in the carbonic acid they drink in, tartaric acid 
may be produced (A.) In the dark they absorb oxygen and give off 
carbonic acid. If the bulk of this latter gas which escapes be less than 
that of the oxygen which enters, a portion of the sugar or gum of the 
sap may, as above explained (B.), be converted into tartaric acid. 

We have as yet no experiments which enable us to say by Avhich of 
these modes the tartaric acid is really produced in such plants — or 
whether it may not occasionally be compounded by both methods. 

In green fruits also, in the sour grape for example, it may, in like 
manner, be produced by either method. The only experiments we yet 
possess, those of De Saussure, though not sufficient to decide the point, 
are in favour of the former explanation (A.) In the estimation of this 
philosopher, the proportion of the oxygen of the carbonic acid which is 
retained by the fruit, is sufficient to account for the acidity it gradually 
acquires. 

2°. Malic and citric acids. — These acids are represented (p. 127) by 
the common formula; C4 Hg O4. They may be produced from water 
and carbonic acid, if three-fourths only of the oxygen of the latter be 
given off. Thus 



4 of Carbonic Acid = C4 O3 
2 of Water . . = H2 Og 



Malic Acid. 



Sum , . =C4 H2 Oio = C4 H2 O4 -f 60. 



That such a retention of one-fourth of the oxygen of the carbonic acid 
occasionally takes place in the green fruit, is consistent with the obser- 
vations of De Saussure. The lime and the lemon are fruits on which 
the most satisfactory experiments might be made with the view of fi- 
nally determining this point. 



142 CONVERSION or ACIDS INTO SUGAR. 

III. This formation of acid proceeds for a certain time, the fruit be- 
coming sourer and sourer ; the acidity then begins to diminish, sugar is 
formed, and the fruit ripens. The acid rarely disappears entirely, even 
from the sweetest fruits, until they begin to decay ; a considerable por- 
tion of it, however, must be converted into grape sugar, as the fruit ap- 
proaches to maturity. This conversion may take place in either of two 

ways. 

1°. By the direct evolution of the excess of oxygen. Thus 
3 of Tartaric Acid = C12 Hg O15 
6 of Water . . . = H3 Og 

Grape Sugar. 

Sum . . . = C,2 H12 O2, = Ci2 H12 0,2 -h 90. 

> V ' 

Or grape sugar may be formed from 3 of tartaric acid and 6 of the water 
of the sap, by the evolution, at the same time, of 9 of oxygen. Citric 
and malic acids, in the same proportion, would form grape sugar by the 
evolution of 6 of oxygen only. 

Do fruits, when they have reached their sourest state, begin thus to 
give off an excess of oxygen ? I know of no experiments which as yet 
decide the point. 

2°. By the absorption of oxygen and the evolution of carbonic acid. 
Thus in the case of tartaric acid, 
1 of Tartaric Acid = C4 Ho O5 
1 of Oxygen . . . = O, 

^jith of Grape Carbonic 

Sugar. Acid. 

Sum . . . = C, a, 0, = C2 H2 O, + 2 CO2 
Where one of oxygen is absorbed and two of carbonic acid given off. 
Or in the case of the malic and citric acids, 

1 of Malic Acid = C4 H2 O^ 

2 of Oxygen . . = O^ 



'A 


th of Grape 




Carbonic 




Sugar. 




Acid. 


= c 


2 H2 O2 


+ 


2CO2 



Sum . . = C4 H, O2 

Where 2 of oxygen are absorbed and 2 of carbonic acid given off. 

We know from the experiments of Berard that, when unripe fruits 
are plucked, they do not ripen if excluded from the access of oxygen 
gas— but that in the air they ripen, absorbing oxygen at the same time, 
and giving off carbonic acid.* This second method (2°) therefore ex- 
hibits the more probable theory of the ripening of fruits after they are 
plucked; and if— as they become coloured — fruits imitate the petals of 
the flower in absorbing oxygen from the air and giving off carbonic acid, 
it will also represent the changes which take place when they are per- 
mitted to ripen on the tree. 

During the ripening of the fruit, it has been stated that the woody or 
cellular fibre it contains gradually diminishes, and is converted into su- 
gar. This is familiarly noticed in some species of bard or winter pears. 
In sour fruit, the cellular fibre seldom exceeds 2^ per cent, of their 
whole weight ; — in ripe fruits, however, it is still less, and as the con- 
stitution of this substance is so analogous to that of grape sugar, there is 
no difficulty in understanding that it may be readily converted into the 
latter, though the immediate agency by which the transformation is 
effected is as yet unknown to us. 



CHANGES AFTER THE FRUIT HAS RIPENED. 143 

§ 5. Of the chemical changes which take place after the ripening of 
the fruit and seed. 

When the seed is fuily ripe, the functions of annual plants are dis- 
charged. They no longer require to absorb and decompose carbonic 
acid, for their growth is at an end. Their leaves begin, therefore, to 
take in oxygen only, become yellow, and prepare along with the entire 
plant, for being finally resolved again into those more elementary sub- 
stances from which they were originally compounded. 

On trees and perennial plants, however, a further labour is imposed. 
In the ripened seed they have deposited a supply of food sufficient to 
sustain the germ that may S]:)ring from it, until it is able to seek food for 
itself; but the young buds already formed, — and which are to shoot out 
from the stem and branches in the ensuing spring, — are in reality so 
many young plants for which a store of food has yet to be laid up in the 
iuner bark, and in the wood of the tree or shrub itself. 

In the autumn, the sap of trees and permanent shrubs continues to 
flow rapidly till the leaf withers and falls, and the food of the plant is 
converted partly into woody fibre, as was the case during the earlier 
period of the year, and partly into starch. The former is deposited be- 
neath the inner bark to form the new layer of wood by which the tree is 
annually enlarged ; the latter — partly in the same locality, as in the 
birch and pine — partly throughout the substance of the wood itself, as in 
the willow — while in the palm trees and cycadeae, it is intermingled 
with the central pith. The chemical changes by which the food is ca- 
pable of being converted into these substances have already been con- 
sidered. They proceed during the entire autumn, do not cease so long 
as the sap continues to move, and even in the depth of winter slowly and 
silently operate in storing up farinaceous matter — in readiness, like the 
starch in the seed, to minister to the nourishment of the young bud, when 
the warmth of the coming spring shall awaken it from its long sleep. 

§ 6. Of the rapidity loith which these changes talce place, and the 
circumstances by which they are promoted. 

But remarkable as those chemical changes are, the rapidity with 
which they sometimes take place is no less surprising. 

From carbonic acid and water we have seen that the plant, by very 
intelligible processes, can extract the elements of which its most bulky 
parts consist — and can build them up in many varied ways, most of whicli 
are probably beyond the reach of imitation. But who can understand or 
explain the extraordinary activity which pervades the entire vascular 
system of the plant, when circumstances are favourable to its growth? 

A stalk of wheat has been observed to shoot up three inches in as 
many days, of barley six inches in the same time, and a vine twig 
almost two feet, or eight inches a day (Du Hamel). Cucumbers have 
been known to acquire a length of twenty-four inches in six days, and 
in the Botanic Garden at Brussels I was shown a bamboo five inches in 
diameter, which had increased in height nine feet in twenty-seven days, 
sometimes making a progress of six to eight inches in a day. In our 
climate we meet with few illustrations of the rapidity with which plants 
are capable of springing up in the most favourable circumstances, and 
the above examples probably give us only an imperfect idea of the ve- 



144 INFLUENCE OF SALINE SUBSTANCES AND MAKUHES. 



1 



locity with which the bamboo, the pahn, the tree fern, and other vascu- 
lar plants, may grow in their native soil and climate. And with what 
numerous and complicated chemical changes is the production of every 
grain of the substance of these plants attended — how rapidly must tlie 
food be selected and absorbed from the air and from the soil — how 
quickly transformed and assimilated ! 

The long period of time during which, year after year, these changes 
may proceed in the same living vessels, or in the same tree, is no less 
wonderful. Oaks have lived to an age of 1500 or 2000 years — yew 
trees to 3000 years — and other species are mentioned as having flour- 
ished from 4500 to 6000 years ; while even a living rose tree {rosa 
canina) is quoted by Sprengel as being already upwards,of 1000 years 
old. — [Sprengel, Lehre vom Diinger, p. 76.] 

The rapidity of the growth of a plant, and the length of its life, are 
equally affected by circumstances. On a knowledge of these circum- 
stances, and of the means of controlling or of producing them, the en- 
lightened practice of agriculture is almost entirely dependent. 

Over the natural conditions on which vegetation in general depends, 
we can exercise little control. By hedge-rows and plantations we can 
shelter exposed lands, but, except in our conservatories and hot-houses, 
the plants we can expect to cultivate with profit will always be deter- 
mined by the general climate in which we live. So the distribution of 
rain and sunshine are beyond our control, and though it is ascertained 
that a thundery condition of the atmosphere is remarkably favourable to 
vegetable growth, [Sprengel, Lehre vom Diinger, p. 73], we cannot 
hope that such a state of the air will ever be induced at the pleasure or 
by the agency of man. But under the same natural conditions of cli- 
mate, there are many artificial methods by the use of which it is within 
our power to accelerate the growth, and to increase the produce, of the 
most valuable objects of ordinary culture. 

Thus the germination of seeds in general is hastened by watering with 
a solution of chlorine (Davy), or of iodine or bromine (Blengini), and 
Davy found that radish seed which germinated in two days when wa- 
tered with solutions of chlorine or sulphate of iron, required three when 
watered with very dilute nitric acid, and five with a weak solution of 
sulphuric acid. 

It is familiarly known also in ordinary husbandry, that the applica- 
tion of manures hastens in a similar degree the development of all the 
parts of plants during every period of their growth — and largely increases 
the return of seed obtained from the cultivated grains. Ammonia and 
its compounds likewise, and nitric acid and its compounds, with many 
other saline substances existing in the mineral kingdom and occurring in 
soils, or which are produced largely in our manufactories, have been 
found to produce similar effects. 

It would be out of place here to enter upon the important and interest- 
ing field opened up to us by a consideration of the influence exercised 
by these and other substances, in modifying both in kind and in degree the 
chemical changes which take place in living vegetables. The true mode 
of action of such substances — iheir precise effects — the circumstances 
under which these effects are most certainly produced — and the theoreti- 
cal views on which they can be best accounted for — will form a subject of 
special and detailed examination in the third part of the present lectures. 



; 

I 



LECTURE VIII. 

How the supply of food for plants is kept up in the general vegetation of the globe.— Propor- 
tion of their food drawn by plants from the air.-Supply of carbonic acid.-Supply ofammo- 
nia and nitric acid.— Production of both in nature.— Theory of their action on hving vege- 
tables. — Concluding observations. 

Having shown in the preceding Lecture in what way, and by what 
chemical changes, the substances of which plants chiefly consist may 
be produced from those on which they live, — there remains only one 
further subject of inquiry in connection with the organic constituents of 
plants. 

Plants, as we have already seen, derive much of their sustenance from 
the carbonic acid of the atmosphere ; yet of this gas the air contains only 
a very small fraction, and in so far as experiments have yet gone, this 
fractional quantity does not appear to diminish — how, then, is the sup- 
ply of carbonic acid kept up ? 

Again, plants most probabl}'^ obtain much of their nitrogen either from 
ammonia or from nitric acid ; and yet, neither in the soil nor in the air 
do these compounds permanently exist in any notable quantity, — whence 
then is the supply of these substances brought within the reach of plants? 

The importance of these two questions will appear more distinctly, if 
we endeavour to estimate how much of their carbon plants really draw 
from ihe atmosphere — and how much of the nitrogen they contain must 
be derived from sources not hitherto pointed out. 

§ I. Of the proportion of their carbon which plants derive from the 

atmosphere. 

On this subject it is perhaps impossible to obtain perfectly accurate 
results. • Several series of experiments, however, have been published, 
which enable us to arrive at very useful approximations in regard to the 
proportion of their carbon which plants, growing in a soil of ordinary 
fertility, and in such a climate as that of Great Britain, actually extract 
from the air by which they are surrounded. 

1°. In an experiment made in 1824, upon common borage (Borago 
officinalis), Lampadius found that after a growth of five months (from 
the 3rd of April to the 6th of September) this plant produced ten times 
as much vegetable matter as the soil in which it grew had lost during 
the same period.* In other words, it had drawn nine-tenths of its car- 
hon from the air. 

2°. The experiments of Boussingauit were made, if not with more 
care, at least upon a greater nutnber of plants, and were protracted 
through a much longer period. It is necessary that we should under- 
stand the principle on which they were conducted, in order that we 
may be prepared to place confidence in the determinations at which he 
arrived. 

* The above experiment may have been correctly made, but the result appears at first 
sight too startling to be readily received as indicative of the proportion of their sustenance 
drawn by plants from the air in tfie general vegetation of the globe. 



146 PROPORTIO> OF CARBON DRAW.V FROM THE AIR. 

If we were to examine the soil of a field on which we are about to 
raise a crop of corn — and should find it to contain a certain per-centage, 
say 10 per cent, of vegetable matter (or 5 per cent, of carbon) ; — and 
after the crop is raised and reaped should, on a second examination, 
find it to contain exactly the same quantity of carbon as before, we 
could not resist the conviction, that, with the exception of what was 
originally in the seed, the plant during its growth had drawn from the 
air all the carbon it contained. The soil having lost none, the ait must 
have yielded the whole supply. 

Or if after examining the soil of our field we mix with it a supply of 
farm-yard manure, containing a known weight, say one ton of carbon, 
and when the crop is reaped find as before that the per-centage of vege- 
table matter in the soil has suffered no diminution,* we are justified in 
concluding that the crop cannot, at the utmost, have derived from the 
soil any greater weight of its carbon than the ton contained in the ma- 
nure which had been added to it. 

Such was the principle on which Boussingault's experiments were 
conducted. He determined the per-centage of carbon in the soil before 
the experiment was begun — the weight added in the form of manure — 
the quantity contained in the series of crops raised during an entire rota- 
tion or course of cropping, until in the mode of culture adopted it was 
usual to add manure again — and lastly, the proportion of carbon re- 
maining in the soil. By this method he obtained the following results 
in pounds per English acre, in three different courses of cropping, and 

on the same land : — 

Carbon Carbon Difference, or 

in the in Carbon derived Remarks. 

manure. the crops. from the air. 

( The first was a 5 years' 
course — of potatoes or 
red beet with manure, 
wheat, clover, . wheat, 

CI 11 cano I oats; the second and 

Second do. — — 6839 s I a r 

' most productive rota- 
lion was abandoned on 
account of the climate ; 
the third was a 3 years' 
^ course. 

The result of the first course indicates that — the land remaining in 
equal condition at the end of the four years as it was at the beginning — 
the crops collected during these years contained three times the quantity 
of carbon present in the manure, and therefore the plants, during their 
growth, must on the whole have derived two-thirds of their carbon from 
the air. 

It will be shown in a subsequent section that even when the soil is 
lying naked the animal and vegetable matter it contains is continually 
imdergoing diminution, owing to decomposition and the escape of vola- 
tile substances into the air. It is fair, therefore, to assume that a coa- 

' I need scarcely remark that, in the hands of a good farmer, who keeps his land in good 
heart — the quantity of organic matter in the soil at the end of his course of cropping should 
be as great, at least, as it was at the beginning of his rotation, before the addition of the 
manure. 



First Course 2513 7544 5031 



Third do. — — 3921 



WEIGHT OF CARBON IN THE ATMOSPHERE. 147 

siderable portion of the carbon of the manure and of the soil would 
naturally disappear during the four years' cropping above-mentioned, 
and that, therefore, the proportion of carbon derived from the air in 
Boussingault's experiments, must have been really considerably greater 
than is indicated by the numerical results. 

Let two-thirds of the entire quantity of carbon contained in a series of 
crops be taken as the average proportion, [Lecture IL, p. 31,] which, on 
cultivated land in our climate, must be derived from the air in the form 
of carbonic acid — and let the average weight of the dry crop reaped be 
estimated at a ton and a half per acre. Then, if the crop contain half 
its weight of carbon,* the plants grown on each acre must annually ex- 
tract from the air 10 cwt. or 1120 lbs. of carbon in the form of carbonic acid. 

§ 2. Of the relation which the quantity of carbon extracted hy plants from 
the air, hears to the whole quantity contained in the atmosphere. 

But the question will here at once suggest itself to you— ^dops not the 
quantity thus extracted from the air really form a very large proportion 
of the whole weight of carbon which is contained in the atmosphere ? A 
simple calculation will give us clear ideas in regard to this interesting 
point. 

We have already seen that, by the results of De Saussure, the aver- 
age quantity of carbonic acid in the atmosphere of our globe may be 
estimated at -r;-^-^ part of its entire bulk. This is equal very nearly 
to 3/00 of its weight. f Or taking the whole weight of the atmosphere 
at 15 lbs. on the square inch — that of the carbonic acid will be 0*009 lbs. 
or 63 grs. per square inch. But as carbonic acid contains only 27| per 
cent, of its weight of carbon, the weight of this element which presses 
on each square inch of the earth's surface is only 17f (17-39) grs. Upon 
an acre this amounts to 7 tons.} 

But if the crop on each acre of cultivated land annually extracts from 
the air half a ton of carbon, the whole of the carbonic acid in the atmos- 
phere would sustain such a vegetation over the entire globe for 14 years 
only. And if we even suppose such a vegetation to extend over one 
hundredth part of the earth's surface only, it still appears sufficient to 
exhaust the carbonic acid of the air in 1400 years. 

* Boussingault states, that of all the plants usually cultivated for food— so far as his experi- 
ments have gone— the Jerusalem artichoke draws the largest portion of its sustenance from 
the air — or yields the greatest uieight of food from the smallest ueighl of manure. It is true 
generally indeed that ail those plants, "which, like the Jerusalem artichoke and the white 
carrot, grow freely on sandy soils containing little vegetable matter and with the addition 
of little manure, extract the greatest proportion of their sustenance from the air. Such 
plants, therefore, are likely to prove the most profitable articles of culture where such soils 
and a scarcity of manure simultaneously prevail. 

t The mean of 225 experiments made by De Saussure between 1827 and 1829 gave as 
above stated about 4-10000 or l-2o00ih part for the mean bulk of the carbonic acid in the air, 
which is nearly 6-lOOOihs of its whole weight. Among these observations the maximum 
was 5-8 ten-thousandths, the minimum 3-15. If we take the maximum bulk at 6-10000th3 
of the air — the maximum weight of the carbonic acid is nearly 9-lOOOOtlis of that of the at- 
mosphere. In elementary works it is generally stated in round numbers at l-lOOOth of the 
weight of the air, but if the best experimental results we possess are to be any guide to us, 
this is at least one-third too high. 

It is also of consequence to remark, that this estimate of the whole weight of the carbonic 
acid in the air is founded on the supposition that, in the highest regions of the atmosphere, 
the carbonic acid is present in a proportion nearly equal to that in which it is found imme- 
diately above the earth's surface — which is by no means established. 

X I5'583 lbs.— £Ui acre being 4840 square yards, containing each 1296 square inchesi 



148 HOW THE SUPPLY OF CARBONIC ACID IS RENEWED- 

A very short period, compared even with the limits of authentic his- 
tory, has yet elapsed since experiments began to be made on the true 
constitution of the atmosphere ; we have no very trustworthy data, 
therefore, on which to found a confident opinion in regard to the perma- 
nence of the proportion of carbonic acid which it now contains. The 
later observations of De Saussure do give a considerably lower estimate 
of the quantity of this acid in the air than that which was deduced from 
the results of the earlier experimenters; but the imperfection of the 
modes of analysis formerly adopted was too great, to justify us in rea- 
soning rigorously from the inferences to which they led. We cannot 
safely conclude from them that the proportion of carbon in the atmos- 
phere has really diminished to any sensible extent during this limited 
period; while the recorded identity of all the phenomena of vegetation 
renders it probable that the proportion has not sensibly diminished even 
within historic times. 

From what sources, then, is the supply of carbonic acid in the atmos- || 
phere kept up? — and if the proportion be permanent, by what compen- T 
sating processes is the quantity which is restored to the atmosphere 
produced and regulated ? 

§ 3. How the supply of carhonic acid in the atmosphere is renewed 

and regulated. 

On comparing, in a previous lecture, the quantity of rain which falls 
with that of the watery vapour actually present in the air, we saw rea- 
son to believe that even in a single year the same portion of water may 
fall in rain or dew and ascend again in watery vapour several succes- 
sive times. Is it so also with the carbon in the air ? Does that which 
feeds the growing plant to-day, again mount up in the form of carbonic 
acid at some future time, ready to minister to the sustenance of new 
races, and to run again the same round of ever- varying change ? Such 
is, indeed, the general history of the agency of the carbonic acid of the 
atmosphere ; but when once it has been fixed in the plant it must pass 
through many successive changes before it is again set free. The con- 
ditions, also, under which it is restored to the atmosphere are so diver- 
sified, and the agencies by which, in each case, it is liberated, are so 
very distinct, as to require that the several modes by which the carbon 
of plants is reconverted into carbonic acid and returned to the air, should 
be made topics of separate consideration. 

1. — ON THE PRODUCTION OF CARBONIC ACID BY RESPIRATION. 

The air we breathe when it is drawn into the lungs, contains -^-^Q^ih 
of its bulk of carbonic acid ; when it returns again from the lungs, the 
bulk of this gas amounts, on an average,* to gV^ ^^ ^^e whole ; or its 
quantity is increased one hundred times. 

The actual bulk of the carbonic acid emitted from the lungs of a sin- 
gle individual in 24 hours varies exceedingly ; it has been estimated- 
however, on an average, to contain upwards of five ounces of carbon. f 

• It varies in different indiviriuals from 2 to 8 per cent, of the expired air. In animals it 
varies also with the speries. The air from the lungs of a cat contains from 5h to 7 per cent., 
of a doa from 4.^ to 6i, of a rabbit from 4 to 6, and of a pigeon from 3 to 4 per cent, of the 
whole bulk. — Dulong, Anrial. de Chiin. etde Phys., Ihira Series, /., p. 455. 

t Davy, and Allen, and Pepys, estimated the weight of carbon evolved in a day atupwai'ds 
of 11 ounces, a quantity which all writers have concurred in receiving with suspicion. 



THE COMBUSTION OF ORGANIC MATTKfe. 149 

A full grown man, therefore, gives off from his lungs, in the course of a 
year, upwards of 100 lbs. of carbon in the form of carbonic acid. 

If the (|uantity of carbon thus evolved from the lungs be in proportion 
to the weight of the animal, a cow or a horse ought to give off six times 
as much as a man.* From indirect experiments, however, Boussin- 
gault estimated the quantity of carbon actually lost in this way by a cow 
at 2200 grammes in 24 hours, and by a horse at 2400 grammes. — [Ann. 
de Ckhn. el de Phys., Ixxi., pp. 127 and 136.] These quantities are equal 
to 6 or 7 times the amount of carbon given off from the lungs of a man. 

If we suppose each inhabitant of Great Britain, young and old, to ex- 
pire only 80 lbs. of carbon in a year, the twenty millions would emit 
seven hundred thousand tons; and, allowing the cattle, sheep, and all 
other animals, to give off twice as much more, the whole weight of 
carbon returned to the air by respiration in this island would be about 
two millions of tons, or the quantity abstracted from the atmosphere by 
four millions of acres of cultivated land. 

Whence is all this carbon derived ? It is a portion of that which has 
been conveyed into the stomach in the form of food. Suppose the car- 
bon contained in the daily food of a full grown man to amount to one 
pound — which is a large allowance — then it appears that, by the ordi- 
nary processes of respiration, at least one-third of the carbon of his food 
is daily returned into the air. 

In other animals the proportion returned may be different from what 
it is in man, yet the life of all depends on the emission to a certain ex- 
tent of the same gas.f And since all are sustained by the produce of 
the soil, it is obvious that the process of animal respiration is one of 
those methods by which it has been provided that a large portion of the 
vegetable productions of the globe should be almost immediately re- 
solved into the simpler forms of matter from which it was originally 
compounded, and again sent up into the air to minister to the wants of 
new races. 

II. — ON THE PRODUCTION OF CARBONIC ACID BY COMBUSTION. 

Another important source of carbonic acid is'familiar to us in the re- 
sults of artificial combustion. 

In the previous lecture I have shown how, by the action of the sun's 
rays upon the leaf, the carbonic acid absorbed from the atmosphere is 
deprived of its oxygen, and its carbon afterwards united to the elements 
of water for the production of woody fibre. During the process of com- 
bustion, this labour of the living leaf is undone — the carbon is made to 
combine anew with the oxygen of the atmosphere, and the vegetable 
matter is resolved again into carbonic acid and water. 

Thus, when wood (woody fibre) is burned in the air, oxygen disap- 
pears, and carbonic acid and watery vapour are alone produced. The 
theory of this change is simple. 

* Estimating the ordinary weight of a man at 150, and of a cow at 800 to 900 lbs. — See 
Sprengel, Lehre vom Dilnger, p. 208. 

' That the proportion must be leas in the larger animals is certain, since the daily food of 
a cow may be stated generally as equivalent to 25 lbs. of hay, containing upwards of iO lbs. of 
carbon. If one-third of this were given off from the lungs, the quantity of carbon (3| lbs.) 
evolved would be ten times greater than was indicated by the experiments of Boussingault, 
and nearly double of what the weight of a cow, compared with that of a man, requires. 



150 PRODUCES CARBONIC ACID AND WATER. 

It will be recollected (p. 135) that in forming an equivalent of woody i| 
fibre or of sugar, 24 of oxygen were given off, chiefly by the leaf — so in ' ' 
again resolving these substances into carbonic acid and water, 24 of oxy- 
gen are absorbed. Thus — 

1 of Woody Fibre = Ci 2 Hg O3 
24 of Oxygen . = 0,4 

12 of 8 of 

Carbonic Acid. Water. 

= 12CO, 4- 8HO. 



Sum . . . 

Or, 1 of Cane Sugar 
24 of Oxygen . . 


C12 "8 O32 

= C12 tlio Ojo 

024 



12 of 10 of 

Caa'bonic Acid. Water. 

Sum. . . =Ci2 Hio O34 =12CO2 + 10HO 

The same law holds in regard to all other vegetable substances. They 
are resolved into carbonic acid and water, in proportions which neces- 
sarily vary with the chemical constitution of each. 

It applies also to all bodies of vegetable origin, among which nearly 
all combustible minerals maybe reckoned. The peat and coal we burn 
in our houses and manufactories, when supplied with a sufficiency of 
atmospheric air, are resolved during combustion into carbonic acid and 
watery vapour. 

Some vegetable substances contain a small quantity of nitrogen. 
When these are burned, this nitrogen escapes into the atmosphere, — 
generally in an uncombined state, — and mingles with the air. So in 
animal substances, nearly all of which contain nitrogen as an essential 
constituent. During perfect combustion the whole of the carbon is dis- 
sipated in the form of carbonic acid, while the nitrogen rises along with 
it in an elementary state- 

The result of this uniform subjection of all combustible matter to the 
operation of this one law, is the ccfnstant production on the surface of 
the globe of a vast quantity of carbonic acid ; — the re-conversion of large 
masses of organic matter into the more elementary compounds from 
which it was originally formed. 

How interesting it is to contemplate the relations, at once wise and 
beautiful, by which through the operation of such laws, dead organic 
matter, intelligent man, and living plants, are all bound together ! The 
dead tree and the fossile coal lie almost useless things in reference to 
animal and vegetable life, — man employs them in a thousand ways as 
ministers to his wants, his comforts, or his dominion over nature — and 
in so doing, himself directly though uncon.sciously ministers to the wants 
of those vegetable races, which seem but to live and grow for his use and 
sustenance. 

It is impossible to say what proportion of the carbon absorbed during 
the general vegetation of the globe, is thus annually restored to the at- 
mosphere by the burning of vegetable matter. That it must be very 
great, will appear from the single fact, that by far the greater part of the 
globe is dependent for its supply of fuel on the annual produce of its 
forests; — while even in those more favoured countries where mineral 
coal abounds, the quantity of wood consumed by burning falls but little 
short of the entire yearly growth of the land. 



il 



LAW OF THE DECAY OP VEGETABLE MATTER. 151 

In connection with this subject, I must draw your attention to one in- 
teresting, as well as important, fact. I have spoken of coal as a sub- 
stance of vegetable origin, and there is no doubt that all the carbon it 
contains once floated in the air in the form of carbonic acid. But the 
period when it was so mixed with the atmosphere is remote almost be- 
yond conception. When, therefore, we raise coal from its ancient bed 
and burn it on the earth's surface, we add to the carbon of the air a por- 
tion which has not previously existed in the atmosphere of our time. 

The coal consumed in Great Britain alone is estimated at 20 millions 
of tons, containing on an average at least 70 per cent., or 14 millions of 
tons of carbon. But if the annual produce of an acre of cultivated land 
contain half a ton (p. 147) of carbon derived from the air, the coal con- 
sumed in this country would supply carbonic acid to the crops grown 
upon 28 millions of acres. Or, since in Great Britain about 34 millions 
of acres are in cultivation (p. 12), the coal we annually consume produces 
a quantity of carbonic acid which is alone sufficient to supply food to the 
crops that groiv upon seven-eighths of the arable land of this country. 

IH. PPvGDUCTION OF CARBONIC ACID BY THE NATURAL DECAY OF VEGE- 
TABLE MATTER. LAW OF THIS DECAY. 

Over large tracts of country in every part of the globe, the vegetable 
productions of the soil are never cropped or gathered, but either accumu- 
late — as occasionally in our peat bogs; or decay and gradually disappear 
— as in the jungles of India or in the tropical forests of Africa and South- 
ern America. 

^he final results of this decay are the same as those which attend 
upon ordinary combustion, but the conditions under which it takes place 
being different, the immediate results are to a certain extent different 
also. 

When a vegetable substance is burned in the air, the oxygen of the at- 
mosphere is the only material agent in effecting the decomposition. 
The carbon of the burning body unites directly with this oxygen and 
forms carbonic acid. 

In the natural process of decay, however, at the ordinary temperature 
of the atmosphere, vegetable matter is exposed to the action of both air 
and water ; these both co-operate in inducing and carrying on the decom- 
position, and hence carbonic acid is not, as in the case of combustion, the 
chief or immediate result. 

A detail of all the steps through which vegetable matter is known to 
pass before it is finally resolved into carbonic acid and water, would be 
difficult for you to understand, and is here unnecessary. A general 
view of the way in which by the united agency of air and water, the 
decay of organic substances is effected and promoted, may be made 
very intelligible, and will sufficiently illustrate the subject for our pre- 
sent purpose. 

In combustion, as we have seen, the whole of the vegetable substance 
is resolved directly into carbonic acid and water, at the expense of the 
oxygen of the atmosphere. In natural decay a small and variable por- 
tion only is so changed, but to the extent to which this change does take 
place carbonic acid is directly formed and sent up into the air. Suppose 
such a change — a slow combustion in reality — to take place to a certain 



152 BY NATURAL DECAY IT IS FINALLY RESOLVED 

extent, and let us consider what becomes of the remainder of the vegeta- 
ble matter. 
1°. If we add 

6 of Carbonic Acid . . = Cg O13 

to 6 of Light Carburetted ? p u 

Hydrogen (CH^) $~ ^^ "^2 



we have the sum . . = C12 H12 Ois? or, one of 
grape sugar; — that is, one of grape sugar may be formed out of the ele- 
ments of 6 of carbonic acid, and 6 of light carburetted hydrogen. Or, 
conversely, grape sugar being already produced, it may be resolved or 
decomposed into these two compounds in the same proportions, without 
the aid of the oxygen of the atmosphere. 
2°. So if to 

1 of Woody Fibre = C,2 H^ O3 
we add 4 of Water . . = H4 O4 

Carbonic Light Carbu- 

Acid. retted Hydrogen, 

we have, as before, C,2 H12 C)i2 ^= 6CO2 + 6 CH2; 

Or by the aid of the elements of 4 atoms of water, w^oody fibre may be 

resolved into 6 of carbonic acid and as many of light carburetted 

hydrogen. 

3°. Again, in the case of a vegetable acid, if to 

1 of Tartaric Acid = C4 Hg O5 

we add 1 of Oxygen . . = Oj 

Carbonic Light Carbu- 

Acid. retted Hydrogen. 

. we have C4 H2 0„ = 3 CO2 + CHg ; 
That is, by the aid of one of oxygen from the air, one of tartaric acid 
may be resolved into 3 of carbonic acid, and 1 of light carburetted 
hydrogen. It is easy to see how any other of the more common vegeta- 
ble productions may — either at the expense of its own elements, as in 
grape sugar — or by the aid of those of water, as in woody fibre — or of 
the oxygen of the atmosphere, as in tartaric acid — be resolved into car- 
bonic acid and light carburetted hydrogen, in certain proportions. 

Now, such a resolution does really take place to a considerable extent 
in nature, during the decay of organic substances in moist situations. 
Hence the evolution of light carburetted hydrogen from dead vegetable 
matter in marshy places and stagnant pools — hence the production of 
the same gas in compost heaps, and especially in rich and heated farm- 
yard manure — and hence also its occurrence in such vast quantities in 
many of our coal mines. 

You will now be able to appreciate one of the reasons why this light 
carburetted hydrogen has been supposed by some physiologists (p. 50) 
to contribute as food to the ordinary nourishment of plants. It is pro- 
duced in nature in many and varied situations, and it has been found 
by experiment to exercise a visible influence upon the growth of plants; 
— being so produced where yoimg plants grow, is it never imbibed by 
them ?— being possessed of this influence, is it entrusted with no control 
over the general vegetation of the globe ? 

However this may be, by far the greatest portion of both these gases 
escapes into the air ; — the carbonic acid to fulfil those purposes which 



INTO CARBONIC ACID AND WATER. 153 

have already been considered, — the light carburetted hydrogen to under- 
go a further change, by which it also is resolved into carbonic acid and 
water. Thus, if to 

1 of Light Carburetted Hydrogen = CH2 vve add 
4 of Oxygen = O4 

Carbonic Acid. Water. 



We have CHg O, or CO2 + 2 FlO 

Or one of this gas with 4 of oxygen may be ctianged into 1 of carbonic 
acid and 2 of water. 

Now, when this gas escapes into the air it becomes diffiised through a 
large excess of oxygen, and is thus ready, at any instant, to be decom- 
posed. Through the atmosphere streams of electricity are continually 
flowing, and every wandering spark that passes athwart a portion of 
this mixture decomposes so much of the light gas, and produces in its 
stead the equivalent proportions of carbonic acid and watery vapour. 
Thus it happens that of the vast quantity of this and other combustible 
gases which are continually escaping into the air, so few traces are dis- 
cernible even by the aid of the most refined processes of art. By a wise 
])rovision of nature such substances as are void of use to either animals 
or plants, if not speedily removed from the air altogether, are there con- 
verted into such new forms of matter as are fitted to minister to the ne- 
cessities of living beings. 

Though therefore in the natural decay of vegetable matter in the pre- 
sence of air and moisture, a certain portion of its carbon escapes into the 
air in the form of light carburetted hydrogen, this compound is but a 
step towards the final change into carbonic acid and water. In the soil 
the vegetable matter is continually undergoing decay, various sub- 
stances are produced in greater or less quantity, some solid, some liquid, 
and some gaseous like the light gas of which we have been speaking, — 
but all of them, like this gas, are only hastening — some by one road, so 
to speak, and some by another — towards that final destination which 
sooner or later they are all fated to reach ; when in the form of carbonic 
acid and water they shall be in a condition to minister again to the nour- 
ishment of all plants. 

While in the soil some part of this vegetable matter assumes forms 
which are capable of entering again into the roots of li\dng ])lants, and, 
without further resolution in the air, of being converted by the living 
plant into portions of its own substance. The nature and composition 
of these forms of matter, so far as they are known, will be considered in 
a subsequent lecture. — [See Part II., Lectures XL-XIIL, " On the 
constitution of soils.^^] 

It is upon the final result of this natural decay to which all vegetable 
matter is subject, that the carbonic acid of the atmosphere depends for 
its largest supplies. The rapidity with which organized bodies perish, 
and become resolved into gaseous compounds, depends partly upon the 
climate and partly on the nature of the substances themselves, — but all 
hurry forward to the same end, and it is with diflSculty that we are able 
for a time to arrest or even to retard their steps. It is by this perpetual 
and active obedience of all dead matter to one fixed law that the exist- 
ing condition of things is maintained ; — and thus it happens that either 
by the respiration of the animals which live upon it, by the process of 



154 EVOLUTION OF CARBONIC ACID IN VOLCANIC COUNTRIES. 

combustion, or by that of spontaneous decay, the entire crop of vegeta- 
ble produce is apparently, year by year — taking the average of a series 
of years — resolved into the forms of matter from which it was originally 
buili up ; — and the substances on which plants feed at lengtli restored to 
the air in the precise proportion in which they have been taken from it. 

VI. NATURAL EVOLUTI3N OF CARBONIC ACID IN VOLCANIC COUNTRIES. 

The above apparent conclusion would be absolutely true, were there 
no causes in operation by which the restoration to the air of a portion of 
the carbon of animal and vegetable substances is prevented — and no 
other sources, independent of existing organic matter, from wliich car- 
bonic acid may be supplied to the air. 

If the whole of the carbon be not returned to the air, the carbonic acid 
of the atmosphere may be undergoing diminution; while — if a large 
supply be constantly poured into the air from sources independent of 
vegetable matfer, the proportion of carbonic acid may be continually on 
the increase. 

We have seen that the combustion of fossil coal adds to the air a 
large quantity of carbonic acid which has never before existed in the at- 
mosphere of our time. In many volcanic districts also, carbonic acid is 
observed to issue in large quantity from cracks and fissures in the earth ; 
— accompanied sometimes by water, forming mineral springs, from 
which the copious emisson of gas is readily perceived ; more frequently, 
perhaps, rising up alone, and thus escaping general observation. 

It must obviously be exceedingly difficult to estimate the quantity of 
gas which rises into the air in such circumstances over an extensive 
tract of country, fractured and broken up by volcanic agency — where 
the outlets are numerous, and the rate at which the gas escapes very 
variable. That in many localities it must be very great, however, 
there can be no question. In the ancient volcanic district of the Eifel, 
comprising an area of many square miles around the Laacher See, on 
the left bank of the Rhine, the annual evolution of carbonic acid from 
springs and fissures has been estimated by Bischof at not less than 
100,000 tons, containing 27,000 tons of carbon. In many other districts, 
especially where active volcanoes exist, the volume of gas given ofT 
may be quite as great, though no attempts have hitherto been made to 
estimate its real amount. 

Yet though absolutely large, the quantity of carbonic acid disengaged 
in this way from the earth, is really small when compared either with 
the entire quantity supposed to be present in the atmosphere, or with 
that which is required for the growth of the yearly vegetation of the 
globe. Suppose that from a thousand spots on the earth's surface a 
quantity of carbonic acid equal to the above estimate of Bischof escapes 
constantly into the air, the weight of carbon (27 millions of tons) thus 
diffused through the atmosphere would be only equal to that which is 
yearly drawn from the air by 54 millions of acres of land under cultiva- 
tion (p. 147), and only twice as much as that contained in the coal 
which is annually consumed in Great Britain alone. 

Still if the ivhole of the carbon contained in the produce of the general 
vegetation of the globe be ultimately restored to the air, — either by the 
respiration of animals, by the natural and slow decay of vegetable mat- 



155 CARBON PERMANENTLY WITHDRAWN FROM THE AIR. 

ter, or Dy the more rapid process of combustion, — the constant addition 
of carbonic acid derived from volcanoes, and from the combustion of fos- 
sil coal, should gradually, though slowly, augment the proportion of this 
gas in the air we breathe ; — unless it be perpetually undergoing a per- 
manent diminution, to at least an equal extent, from the operation of 
other causes. In reference to this point there are three circumstances 
which are proper to be considered : — 

1°. It has been observed that, as we recede from the land and ap- 
proach the centre of great lakes, or sail into the open sea, the quantity 
of carbonic acid in the air gradually diminishes. It is therefore inferred 
that the sea is constantly, and to a sensible extent, absorbing carbonic 
acid from the atmosphere, without afterwards restoring it, so far as is 
yet known, by any compensating process. 

2°. The waters which flow into the sea or great lakes constantly 
bear down with them portions of animal and vegetable matter. These 
fall along with the mud which the waters hold in suspension, and are 
permanently imbedded in the deposits of clay, silt, and sand, which are 
continually in the course of formation. 

3°. In many parts of the world, especially in the latitudes north and 
south of 45°, vegetable matter accumulates in the form of peat, becomes 
buried beneath clay and sand, and thus is prevented from undergoing 
tlie ordinary process of natural decay. 

It is impossible to say how much carbon is permanently withdrawn 
from the atmosphere by these several agencies. There is reason to be- 
lieve that it is quite as great as the quantity added to the air by the 
combustion of coal, and by the evolution of carbonic acid in volcanic 
districts. Indeed, the supply from these two sources appears to return 
only a small portion of that carbonic acid which is abstracted from the 
air by the agencies just stated, and which have been in operation during 
every geological epoch. 



Conclusions. — The general conclusions, therefore, which we seem jus- 
tified in drawing in regard to the supply of carbonic acid to the atmos- 
phere are as follow : — 

1°. That a large portion of the carbonic acid absorbed by plants is 
immediately and directly restored to the air by the respiration of the 
animals which feed upon vegetable productions. 

2°. That a still larger portion is more slowly returned by the gra'dual 
re-conversion of vegetable substances into carbonic acid and water dur- 
ing the process of natural decay. 

3°. That yiearly all the remainder is given back in the results of or- 
dinary combustion. 

4°. That a further portion, which has not previously existed in the 
atmosphere of our time, is conveyed to it by the burning of fossil fuel, 
and by the emission of carbonic acid from cracks and fissures in the 
surface of the earth ; yet that the quantity thus added cannot be sup- 
posed to exceed that which is constantly and permanently separated 
from the atmosphere by other causes. 

The balance of all the evidence we possess is probably in favour of 
the opinion that the carbonic acid in the atmosphere is slowK^ diminish- 



156 AMMONIA IN THE AIR — HOW DECOMPOSED. 

ing ; we have, however, no satisfactory evidence either from theory or 
experiment that it has undergone any sensible diminution in our time.* 

§ 4. Of the supply of ammonia to plants. 

In a previous lecture it has been shown that in our cultivated fields 
plants derive a portion of their nitrogen from the manure which is added 
to the soil. But the quantity of this element present in the manure, 
supposing it all taken up and appropriated by the plant, is seldom equal 
to that contained in the series of crops which this manure assists in raising. 

Thus, in the experiments of Boussingault already described (p. 144), 
the manure added previous to the first, or four years' course, contained 

157 parts of nitrogen, while the crops contained 251 parts, — or nearly 
two-thirds more than could be derived from the artificial manure. 

Whence is this excess of nitrogen derived, and in what form does it 
enter into the plant? Liebig replies to these questions, that the whole 
of the nitrogen absorbed by plants enters in the state of ammonia, and 
that the excess above what is present in the manure is drawn either 
from the soil or from the air. This opinion, advanced by so high an 
authority, demands our attentive consideration. 

Ammonia has been detected in many clays, and traces of it may be 
discovered in most soils, but it is not known to be a natural or essential 
constituent of any of the solid rocks of which the crust of the globe is 
composed. These clays and soils, therefore, may be supposed to have 
derived their ammonia from the atmosphere ; and Liebig ascribes the 
fertilizing action of the air upon stiffclays when fallowed, of burned clay 
when applied as a top-dressing, and of gypsum on grasslands [see note 
to page 53], to the larger quantity of ammonia which the surface of the 
soil is by these means caused to absorb and retain. 

There is no question that ammonia is present in the atmosphere in 
small and variable quantity (p. 37). Whence is this ammonia derived, 
and is its quantity sutficient to supply the demands of the entire vegeta- 
tion of the globe ? '1 

When animal substances undergo decay, nearly all the nitrogen they^ 
contain is ultimately separated from the other constituents in the form of 
ammonia. During the decay of plants also, a portion of their nitrogen 
escapes in the state of ammonia. Of the ammonia thus formed, much 
ascends into the air, chiefly in combination with carbonic acid as carbonate 
of ammonia (smelling salts), and much remains in the soil. Were the 
whole of the nitrogen contained in plants and animals to assume the 
form of ammonia when they decay, and to remain in the soil or in the 
air, it would always be within the reach either of the roots or leaves of 
the living races; and thus the same ammonia [or ammonia containing 
the same nitrogen — supposing the hydrogen to have been changed] 
might again and again return into the circulation of new vegetable tribes, 
and be always alone sufficient to supply all the demands of the exist- 
ing vegetation of the globe. 

But of the ammonia thus formed, a portion is daily washed from the 
soil by the rains and carried to the sea» and much more probably is 

In anothei* v/ork ^Chemical Geology) now preparing for publication, I have discussed 
this question in connection with purely Geological considerations and without reference to 
our time ; but it would be out of place to inti'oduce here any train of reasoning which is not 
calculated to throw light on the phenomena of the existing vegetation ot the globe. 



AMMOXIA EVOLVED FROM VOLCANOES. 157 

washed from tne air by the waters of the sea itself, or by the rains which 
fall directly into the wide oceans ; and we know of no compensating 
process by wliich this ammonia can be restored to the air, and again 
made useful to vegetation. 

Besides, of that which still remains in the air much must undergo 
decomposition by natural processes. In treating in a preceding section 
of the evolution of light carburetted hydrogen during the slow decay of 
vegetable matter (p. 153), I have shown how, in consequence of its ad- 
mixture with the oxygen of the atmosphere, this gas is finely decom- 
posed, while carbonic acid and water are produced. Ammonia in like 
manner will burn in oxygen gas, and when mixed with atmospheric air 
may be decomposed by the electric spark — water at the same time being 
formed and nitrogen set free. Thus, 

if with 1 of Ammonia = NH3 
we mix 3 of Oxygen = O3 

3 of water. 1 of nitrogen. 



we have the sum NH3 ©3 = 3 HO -f N 

or, when diffused through the air, 1 of ammonia, with the aid of 3 of 
oxygen, will yield 3 of watery vapour, while the nitrogen may* mingle 
with the air in an elementary form. Can we doubt that ammonia 
is thus decomposed in the air? Not to speak of other forms assumed 
by the electricity of the atmosphere, can the thunder-stormsof the tropi- 
cal regions pass unheeded tiie ammoniacal vapours they must meet 
with in their course ? 

I conclude, tlien, that of the ammonia which is formed from the nitro- 
gen actually existing in animal and vegetable substances during their 
decay, only a coinparatively small portion ever returns again to minister 
to tlie wants of new races. f 

But if plants obtain all their nitrogen from ammonia, t how is this 
waste re])aired — whence are new supplies constantly derived ? 

We have seen that, in certain volcanic countries, carbonic acid is 
evolved in vast quantities from rents and fissures in the earth. In some 
of these districts — and this has been observed more especially in Italy 
and Sicily, and it is said also to some extent in China — ammonia is 
likewise given off, in combination generally with some acid, and most 
frequently with the muriatic acid in the form of sal-ammoniac (muriate 
of ammonia). " 7%is ammonia,'''' Liebig is correct in saying, ''has not 
been produced by the animal organism ;" but he assumes a very doubt- 
ful position when he adds, "-it existed before the creation of human be- 
ings ; it is a part, a primary constituent of the globe itself.^* — [Organic 
Chemistry applied to Agriculture, p. 112.] 

Where, we might ask, has this ammonia existed during all past time 
— from what deep caverns of the earth does it now escape ? 

I say may, because it may at the same time combine with oxygen and form nitric acid. 
—See the following section, p. 239. 

■» I might add, that of the ammonia which does return, and is again absorbed, a portion is 
subsequently decomposed in the interior of Uving plants, as is shown by the evolution of 
nitrogen from the common leaves of some and the flower leaves of others. 

t "Wild plants obtain more nitrogen f rum the atmosphere, in theformofaminonia, than they 
require for their growth, for the water which evaporates through their leaves and blossoms 
emits, after a time, a putrid smell — a peculiarity possessed only by such bodies as contain 
nitrogen."— :[Liebig, Organic Chemistry appliod to Agriculture, ^. 85.] Does the fact here 
staled, justify the conclu.sion which appears to be drawn from it \ 

14 



158 INDIRECT PRODUCTION OF AMMONIA. 

This opinion of Liebig, as well as the paramount influence he as- 
cribes to ammonia over the vegetation of the globe, are based chiefly on 
the fact that we know of no means by which ammonia can be formed 
by the direct union of the liydrogen and nitrogen of which it consists. 

But the production of ammonia, by the indirect union of these ele- 
ments, is daily going on in nature, and can even be effected by differ- 
ent processes of art. Thus — 

1°. When organic substances, which contain no nitrogen, are oxidized 
in the air, ammonia is not unfrequently formed (Berzelius). Hence 
it must be produced in unknown quantity during the annual decay of 
all vegetable substances. 

2°. When organic substances are oxidized in the presence of air and 
water — as when moist iron filings are exposed to the air (Chevallier), 
or when certain oxidized substances are decomposed in the air by 
means of potassium (Faraday), or when metals, such as tin filings, are 
rapidly oxidized by means of nitric acid, ammonia is also produced in 
variable quantity. Hence the absorption of oxygen, even by the inor- 
ganic substances of the soil, may give rise to the formation of ammonia. 
But, 

3*^. The fact which most clearly illustrates the production of am- 
monia in nature, both on the surface of the earth, in the soil, and far in 
the interior near the seat of volcanic fires, is this, that if a currant of 
moist air be made to pass over red-hot charcoal, carbonic acid and am- 
monia are simultaneously formed.* This is in reality only a repetition 
in another form of what takes place, as above stated, when vegetable 
matter decays, or iron filings rust in moist air. The carbon and the iron 
decompose the watery vapour in the air, and combine with its oxygen, 
while, at the instantf of its liberation, the hydrogen of the water com- 
bines with the nitrogen of the air, and forms ammonia. 

The source of the ammonia evolved in volcanic districts, therefore, is 
no longer obscure. The existence of combustible matter in such dis- 
tricts, and at great depths beneath the surface, can in few cases be 
doubted, and the passage of a mixed atmosphere of common air and 
steam over such combustible matter, at a high temperature, appears to 
be alone necessary to the production of ammonia. It is unnecessary, 
then, to have recourse to doubtful speculations in order to account for 
the natural reproduction of ammonia, to a certain extent, in the place 

This experiment is easily performed by drawings, current of mixed atmospheric air. 
and steam through a red-hot gunhEirret filled with well-burned charcoal, and causing the ' 
current, on leaving the barrel, to pass through water acidulated with muriatic acid. After 
a time, the water, on evaporation, will be found to contain traces of sal-ammoniac. What 
thus takes place in a small experiment of this kind must more readily and more largely 
take place in the interior of the earih, where combustible substances at a high temperature 
happen to be exposed to a current of atmospheric air, mixed with watery vapour. 

t A beautiful illustration of the tendency which elementary substances have to unite with 
each other at the instant of their liberation in what cliemists rail their nascent state, is men- 
tioned by Runge, — Einlcitiing in die technisthe Chemie, p. 373. 

If 1 part of hydrate of potash and 20 of iron filings be heated together, hydrogen only is 
given off. 

If 1 of nitrate of potash and 20 of iron filings be heated together, nitrogen only is given off. 

But if 40 of iron filings be mixed with 1 of hydrate and 1 of nitrate of potash, and then 
heated, ammonia becomes perceptible. 

The nitrogen and hydrogen being given off together, at the same instant, some portions 
of each find themselves in a condition to unite, and thus ammonia is produced. Tlie same 
result must follow in many natural operations, when hydrogen and nitrogen are set free 
from a previous state of combination, at the same time, and in the presence of one another. 



NITRIC ACID EXISTS LARGELY IN NATURE. 159 

of that which is constantly undergoing decomposition by the agency of 
causes such as those above described. ^ "^ 

r.n^"^ V^A ^"^f,*^?^^^ quantity of ammonia reproduced by these indi- 
rect methods sufficient to replace all that is lost ? Can it be supposed 

t TI^-^ '° ? -^"'f ^r n^^ .""''^>?"" '^'^y ^^^"i'-^ '- These questions will 
be considered m the following section. 

§ 5. O/^i/ig swp;?/?/ of nitric acid to plants. 
In regard to the action of nitric acid upon vegetation it is known— 
1 .mat when, m the form of nitrates of soda, potash, &c., it is 
spread upon the soil, it greatly promotes the growth and luxuriance of 
the crop and increases Us produce ; and 

^ 2°. That, when other circumstancs are favourable to veeetation—as 
in certain districts in India-the presence of an appreciable^iuantity of 
these nitrates adds largely to the fertility of the soil.* ^ ^ 

Ihe same effects are unquestionably produced by the addition of am- 
monia or by us natural presence in the soil. The beneficial influence 
ot both compounds, then, being recognized, the relative extent to which 
each operates upon the general vegetation of the globe will be main- 
ly determined by the circumstances and the quantity in which they res- 
pectively exist or are reproduced. ^ J j ^« 
In regard to the existence of nitric acid, it is not known to form a 
necessary constituent of any of the solid rocks of whic4i the crust of the 
globe IS composed, but is diffused almost universally through the soil 
which overspreads the surface. In the hotter regions of the earth, in 
India in Africa, and in South America (p. 56), it in many places accu- 
muJates in sufficient quantity to form incrustations of considerable thick- 
ness over very large areas, and in many more it can be separated by 
washing the soil. Even in the climates of Northern Europe, it is rare- 
ly absent from the water of artificial wells, into which the rains, after 
liltering through the surface, are permitted to make tlieir way.- 

On the whole, nitric acid and its compounds appear to exist, ready 
lormed in nature, in larger quantity than either ammonia or any of its 
compounds. j' ■^ 

debterilo^t/^iJUm""' *";? other interesting notices, regarding Indian agriculture, I am in- 
»n wM. ?k! ,r ,^'"^' of Barociian, in Renfrewshire, whose long residence in the disWc^s 
LT?ny ve^rviluabVf '''" ^''''' ''''''''' ''' '''''' '" P^'^'^^''^^' airicultur "renders hS lei 

ouZ^'Sj'pSvT^^^^ nearPatna, where a large proportion 

DrodLin^ 9 anH c^l!^' o^^' '* P^'of^'^'^'d, are considered the most fertile in Bengal 
?I"tecLlfriOnt/c^K'''"1'.^^™P'.y^^''^ 'The natives of these districts, particularly a 
bScrS' a?e nfhV?rHt''V^'^-^'l'^'"T^.' "'^° ^^'''tivafe the best land, and produce t^he 
preeS wifh««l npf f H^'T^^^^^ "'"'•■ ^•^'^^ ^'"^ "^'^'^^ f'""'" ^^ells so strongly im- 
Cfn^ nnH i '^^^'^^"''i'^'^^'' salts as to be quite brackish, and they consider onion«. 

seed is sivvu bu f^S^n w'r^M^'"^ '^v^*"^ *' *^"°"^^ "^ '"^•" ^'*'h>" ^ weelc or two after the 
fue7but^[h"e'^Q'^fi>i"pr^Lf "f ,?"y l?^""":^ '^^"" ^^"^^' «« t^*" f'""^ «f ^^^ '•atlle is used for 

S .pi\?.L^e'^rchreiry"^'r^.:?X^^ ^prnt'""^^ ^"' '' ^"^"^^ ^°«^' ^"^ "^« '' - ^ -- 

v;>^i^tsoit\ol^^^ the rotation of crops, and the ad- 

rice Indian corn or S.f''^^ «^"^« '^"d is almost constantly in 

seSon'' ' "'^ "™'"et» touring the rainy season, and in wheat or peas during the'dry 

IrJtJsol-poush Urnri t '^' "^'g^bo»rhood of Berlin (Mitscherlich), in the form of ni- 



♦! 



160 FORMATION OF NITRIC ACID. 

Of these nitrates, as they do of ammonia, the rivers must be continu- 
ally bearing a portion to the sea, but there are in nature unceasing pro- 
cesses of reproduction, by which not only this waste of the nitrates is 
repaired, but that further waste, also, which is caused by their absorp- 
tion into the roots and subsequent decomposition in the interior of plants. , ^ 
Let us shortly consider tliese processes of reproduction. Ij 

1°. When a succession of electric sparks is passed through common * ' 
air, nitric acid (NO5) is slowly but sensibly formed. The currents of 
electricity which in nature traverse the atmosphere must produce the 
same effect, and the passage of each flash of lightning through the air 
must be attended by the formation of some portion of this acid. Ij 

After a thunder-storm plants appear wonderfully refreshed; in thun- « 
dery weather they grow most luxuriantly, and other things being equal, 
those seasons in which there is much thunder are observed to be the 
most fruitful. Some have ascribed these results to the immediate agency 
of electricity on the growth of plants. — [Sprengel, Chemie, I., p. 99.] 
It is not equall}^ possible that they may be connected with this necessary 
production of nitric acid ? 

In the rain which fell during 17 thunder-storms, Liebig found nitric 1 
acid always present and generally in combination with lime and am- I 
inonia. In the rain which fell on 60 other occasions, he could detect it 
only twice. In minute quantity nitric acid is difficult to detect. How 
much then must be formed in a thunder-storm, even in our climate, to 
make the presence of this acid always appreciable in the rain that falls 
— how vast a quantity in those warmer climates where such storms are 
so frequent and so appalling! 

2°. When a mixture of ammonia with oxygen gas is exploded by 
passing an electric spark through it, a quantity of nitric acid is formed, 
even when the oxygen is not sufficient to oxidize the whole of the am- 
monia* (Bischof). Hence, if in the air, as we have seen reason to be- 
lieve, the ammonia given off' from decaying animal matters, and from 
other sources, be decomposed by the atmospheric electricity, — there will 
necessarily be formed at the same instant a portion of nitric acid, at the 
expense of the nitrogen of the ammonia itself. This nitric acid will, as 
necessarily, combine with some of the ammonia which still remains in 
the air. Hence the existence and production of nitrate of ammonia in 
the atmosphere, and the consequent presence of this acid along with am- 
monia in rain water. 

Thus the very cause which in the preceding section was shown to 
operate in constantly di?ninishing the amount of ammonia in the air, 
and the operation of which certainly renders im])robable the existence 
of this compound in the atmosphere in the large quantify supposed by 
some [see especially Liebig's Organic Chemistry applied to Agriculture, 
p. 74], this same cause is at the same moment constantly reproducing 
nitric acid. And, though much of what is thus produced must neces- 
sarily, as in the case of ammonia, be carried down to the sea by the 
rains, or be directly absorbed by the waters of the ocean themselves, yet 

* It was shown above (p. 157), that I of ammonia ( NH3 ) requires 3 of oxygen to decom- 
pose it, forming 3 of water, and setting the nitrogen free. But, in reality, as Bischof has 
shown, the nitrogen is not wholly set free, but a portion both of its hydrogen and nitrogen 
combine with oxygen (are oxifUzed) at the same instant, forming simultaneously both water 
(HO), and nitric acid ( NO5 ). 



II 



ARTIFICIAL NITRE BEDS. 161 

it is obvious that in whatever proportion we may suppose the ammonia 
of the air to reach the leaves and roots of plants, in no less proportion 
must the nitric acid, with which it is associated, be enabled id enter into 
the circulating system of the various tribes of living vegetables, that 
flourish on every quarter of the globe. 

3°. Again, we have seen that, during the decay of vegetable substan- 
ces in moist air, ammonia is formed at the expense of the hydrogen of 
the water and of the nitrogen of the air. In consequence of, or in con- 
nection with, such decay, nitric acid is also largely produced in nature. 
The most familiar, as well as the most instructive examples of this 
formation of nitric acid is in the artificial nitre beds of France and the 
north of Europe. These are formed by mixing earth of different kinds 
with stable manure or other animal and vegetable matters, and exposing 
the mixture to the air in long ridges or conical heaps, which are occa- 
sionally watered with liquid manure, and trurned over, to expose fresh 
portions to the air. After a time, perhaps once a year, the whole is 
washed, when the water which comes off is found to contain a variable 
quantity of the nitrates of potash, soda, lime, and magnesia, which are 
employed for the manufacture of saltpetre. In these nitre beds it has 
been observed that the production of nitric acid either does not take plaec 
at all, or only with extreme slowness, unless animal and vegetable mat- 
ter be present in considerable proportion. And yet the quantity of nitric 
acid which is formed is much greater than could be produced by the 
oxidation of the whole of the nitrogen contained in the organic matters 
present in the mixture.* It is also observed that the nitre beds are more 
productive when a portion from one outer face of the heap is lixiviated 
from time to time, and ihe washed earth added to the other side, than 
when the whole is lixiviated at once, and again formed into a heap and 
exposed to the air. 

It appears, therefore, that organic matters are in our climate necessa- 
ry to cause the formation of nitric acid to commence, but that after it has 
begun it will proceed in the same heap for an indefinite period, and at 
the expense apparently of the nitrogen of the air only. 

Compost heaps are in general only artificial nitre beds, often unskil- 
fully prepared and badly managed, producing, however, a certain quan- 
tity of nitrates, to the presence of which their effect on vegetation may 
not unfrequently be ascribed. To this fact we shall hereafter recur. 

The soils in the plains of India, and in other similar spots in the trop- 
ical regions, may be regarded as natural nitre beds, in which, the decay 
af organic niatter being vastly more rapid than in our temperate regions, 
the production of nitric acid is rapid in proportion. f 
4°. But in many localities in which the presence of organic matter is 

• Dumas, Traite de Chemie, II., p. 725. He adds, that 100 lbs. of nifre contain the nitrogen 
3t 75 lbs. of ordinary animal matter, supposed in a dry state, or of 300 or 400 lbs. in its ordi- 

^^ w^^u u^'^'"*"®'"* ^^^^ greater relative proportion of animal matter than is ever 
laded to the heap. 

t We are as yet too little acquainted with the natural history of the district of Arica in 
South Amenca, m which, as already stated (p. 56), the nitrate of soda has been accumulated 
n such lars^e quantity, to be able to say to what special cause the accumulation is due But 
IS, from the description of Mr. Darwin, the locality appears to have been the site of an an- 
nentlake, it is not unlikely that the nitrate may have been derived from the successive 
vashings of a soil similar to that of India, by rains or periodical floods, which for a lon<r ne- 
•lod emptied themselves into or fed the lake. " ^ 



162 NITRE CAVES. — MTRIC ACID FORMED IN THE SOIL. 

not to be recognized in sensible quantity, the production of this acid is 
observed to proceed with a constant and steady pace. Thus, from the 
walls of Certain caves in Ceylon a layer is yearly pared off, which 
yields an abundant crop of saltpetre (Dr. John Davy). The celebrated 
Mammoth cave in Kentucky, situated in a limestone ridge, yields an 
inexhaustible supply of nitrate of lime. During the war with Great 
Britain, fifty men were constantly employed in lixiviating the earth of 
this cave, and in about three years the washed earth is said to become 
as strongly impregnated as at first. Through the cave a strong current 
of air is continually rushing — inwards in winter, and outwards during 
the summer months. On the plaster of old walls, especially in damp 
situations, an efflorescence of this and other nitrates is frequently ob- 
served over every part of Europe. In China, according to Davis, the 
old plaster of the houses is so much esteemed as a manure, that parties 
will often purchase it at the expense of a coating of new plaster. Old 
clay walls, and especially the walls of clay-built huts, are said to be 
very fertilizing to the land, when applied as a top-dressing, and in some 
parts of England, where (he land is poor, the people are said to pile up 
the soil in the form of walls, in order to improve its quality. These lat- 
ter facts seem to indicate that both in China and England nitric acid is 
produced in similar circumstances, and that to its production the ferti- 
lizing action of the old plaster, and of the weathered clay, is alike to be 
attributed. 

In the cultivated soil also, this acid is formed in ordinary circum- 
stances. Braconnot found nitrate of potash in the botanic garden at 
Nancy, in a portion of soil in which poppies {papaver somniferum) had 
grown luxuriantly for ten years in succession — in larger quantity in the 
soil surrounding the interlaced roots of an esclepias incarnata, growing 
in an ordinary flower-pot, with a hole in the bottom — as well as in moss 
earth, in which a plant of euphorbia breoni had been grown in a pot. — 
[Ann. de Chim. et de Phys., Ixxii., p. 33 to 35.] There is little reason 
to doubt, indeed, that nitrates are to be found, in greater or less quantity, 
in all cultivated soils. 

I shall not enter into a detailed inquiry how this nitric acid is formed. ^ 
It is probable that as in the atmosphere ammonia may be decomposed ' 
and give rise to the formation of nitric acid, so in the soil this acid may 
result from a similar decomposition, proceeding more slowly, but accord- 
ing to the same natural laws. In warm climates, indeed, it appears 
certain that the ammonia which is evolved or formed during the decay 
of animal and vegetable substances, does speedily, and to a great extent, 
undergo oxidation,* and thus give rise to the greater abundance of nitric^ 
acid with which the tropical soils abound. 

Thus, in the economy of nature, much ammonia is decomposed in the 
soil also, and hence another cause for the constant diminution of the 
quantity of this compound in addition to those already detailed in the 
preceding section. 

But, besides the portion of this nitric acid, which owes its existence to 

• For the perfect oxidation of 1 of ammonia, no less than 8 of oxygen are required. Thus 

lof lof 3 of 

Ammonia. Nitric Acid. Water. 

NH3+80=:N05 -t- 3HO. 



i 



QUANTITY i:* WHICH IT IS REPRODUCED. 163 

the decomposition of amniouia, much, by far the greatest proportion in 
all probability, derives its origin from the union of the elements of the 
atmosphere itself. This direct union is eifected in the air, as has been 
already shown, by the agency of atmospheric electricity; but it also 
takes place in the soli during the oxidation of the other elements con- 
tained in the organic matters which are there undergoing decay. The 
combination of the elements of ammonia in such circumstances proceeds 
on the principle that bodies, themselves undergoing oxidation, dispose 
other substances in contact with them (in this instance the nitrogen of 
the air) to unite with oxygen also. The presence of lime, potash, &c. 
in the soil, further induces (o this oxidation by the tendency of these sub- 
stances to combine with the acid which is formed by this union of the 
elements of which nitric acid consists. — It is impossible precisely to es- 
timate the quantity of nitric acid produced in these various v^'ays, through 
lliese various agents, an] in these varied circumstances, or to balance it 
aecaratdy against the amount of ai^imonia continually reproduced, as 
we have seen, in nature, wherever the necessary conditions present 
themselves. But, as I formerly concluded, that the amount of nitric 
acid actually existing in the superficial deposits of our globe is greater 
than that of ammonia, so T think that, in regard to the reproduction also 
of these two compounds, the balance is in favour of the former. 

Since, then, nitric acid is fitted, by the solubility of its compounds, to 
enter into the circulation of plants in any quantity — ■since, when applied 
to them, it does undoubtedly promote, in a remarkable degree, the growth 
of plants — and since, in nature, it is continually reproduced in every 
country, and under such varied circumstances — I cannot withhold ray- 
self from the conclusion, that, over the general vegetation of the globe, 
it holds with ammonia at least an equal sway, and is appointed to exer- 
cise at le^st an equal influence over the growth of plants, both in their 
matural ai3d in their cultivated state- 
Still the influence of each is not unvaried by locality or by climate. 
The extent of dominion exercised by the nitrates probably diminishes as 
we recede from the equator, while that of ammonia increases, — it may 
fee in an equal proportion. The reason of this probable variation will 
appear in the following section- 

§ 6. Theory of the action of nitric acid and ammonia. 
These two comi3ounds act so far in common as to yield a supply of 
nitrogen to the plants into which they enter. They do so, however, un- 
der conditions which may be considerably different, and may be attend- 
ed by unlike chemical changes- 

I. THEORY OF THE ACTION OF NITRIC ACID. 

1°. The nhric acid of the nitrates entering into the circulation of the 
roots will ascend to the leaf, and will there be decomposed in the same 
way as the carbonic and other similar acids are, by the action of the 
€un's rays. It is only in the light of day that carbonic acid is decom- 
posed in the green parts of plants — so must it be, generally, with the 
nitric acid which ascends to the leaf Its oxygen will be given off, 
while it, nitrogen may be retained in the circulating s^'stem of the plant. 
The extent to which this decomposition will take place at each passage 



164 THEORY OF THE ACTION OF NITRIC ACID AND OF AMMONIA. 

of the sap through the leaf will depend, in some degree, on the nature 
of the base (whether potash, soda, or lime,) with which the acid is in 
combination, but much more on the intensity of the light to which the 
green parts of the plant are exposed, and on the temperature of the air in 
which the plant happens to grow. 

2°. It is still uncertain whether this acid is capable of being decom- 
posed in the roots or stems of plants where it is excluded from the light, 
though it is very probable that it may be so, especially in cases where 1 
the juices naturally contain substances in which hydrogen is present in * 
excess, or where such compounds make their way into the circulation 
of plants from the manure that may be applied to their roots. 

Thus in the pines, in which turpentine (C40 Hg^) naturally abounds, 
such a decomposition may the more readily occur, inasmuch as it would 
not necessarily imply the production and evolution of any gaseous sub- 
stance. Thus 

1 of Oil OF Turpentine, — C40 ^32 ^^'th the oxygen of 

1 of Nitric Acid (NO3) = O5 gives 



1 of Resin, = C40 H33 O5 

By uniting with the oxygen of the nitric acid, therefore, oil of turpen- 
tine, in such trees, might be changed into resin during its passage 
through the stem, while the nitrogen, being set free, might, at the mo- 
ment of its liberation, unite with other elements to form those parts or 
productions of the iree into which this element enters as a necessary 
constituent. 

The above must be considered merely as an illustration of the kind of 
changes which may possibly take place in the interior of certain plants, 
and in the absence of light, when the nitrates happen to be present. 
Were I to affirm that such changes actually do occur in the presence 
of nitric acid, the theoretical chemist would have a right to expect that 
several collateral questions should be discussed, the consideration of 
which would here be out of place. 

3°. The nitrates may also act in another way, which does not involve 
the necessity of the total decomposition of the acid they contain. We 
know that in nature many substances are capable of inducing chemical 
changes in other compound bodies, without themselves undergoing de- 
composition. Some beautiful illustrations of this have already been 
given in a previous lecture, when treating of the action of sulphuric acid 
upon starch and woody fibre, [Lecture VI.. pp. 113, 114.] But the fact 
which most immediately bears on the influence of the nitric acid in the 
living plant, is that mentioned in j). 126, — that by solution in this acid 
in the cold, starch is converted into a substance having the composition 
of woody fibre. In the interior of the plant changes of this kind may 
be produced by simple contact only, with the nitric acid, so that, with- 
out being decomposed, it may be materially serviceable in promoting 
those molecular changes which are necessary to the healthy and rapid 
growth of the plant. 

II. THEORY OF THE ACTION OF AMMONIA. 

1°. Ammonia is capable of contributing to the growth of the plant, 
by means of the hydrogen, as well as of the nitrogen it contains. We 



I 



IS A31IM0NIA UECOMI'OSKD IN THE DARK? 165 

• 

have seen [notes to pages 136 and 138,] iliaf, according to the rcsulis 
of the best experinjcnis, tlie whole of the oxygen of ilje carbonic acid 
absorbed, is not given oft' by the leaves of all plants e\eii in the sun- 
shine, — while in the dark this gas Is largely and directly injbibed from 
llie air. If in the sap of a plan^ there be present at the same time a 
quantity of ammonia, llie hydrogen of this ammonia may unite directly 
with the oxygen of the carbonic acid, forming water and a proportionate 
quantity of one or other of the several compounds (p. 112), which may 
be represented by carbon and water. Thus 

3 of Carbonic Acid, = C3 Og and the hydrogea of 

2 of Ammo.nia (NH3) = He 

;^' of Grape 3 of 

Sugar. Water. 

giv« . . . . C3 H, Oe = C3 H3 O3 + 3HO 
so that where ammonia is present, and circumstances are favourable, 
sugar or starch may be formed in variable quantity, without the neces- 
sary evolution of oxygen gas. This change will take place in the inte- 
rior of the leaf. And, if the direct decomposition of carbonic acid, and 
the evolution of its oxygen by the agency of the sun, take place at the 
same time — with a rapidity proportioned to the intensity of the light, — 
his simultaneous production of sugar, &c., from the presence of aramo- 
Qia, must aid the increase and growth of the plant; and may be one 
aiain cause of the fertilizing action of this compound, which has been so 
long and so generally recognized. 

When the hydrogen oi^ the ammonia is thus worked up, the quantity 
Df oxygen which escapes from the leaf must be less in proportion; and 
;)«nce another cause (p. 138) for those discrepancies which have been 
observed in regard to the bulk of oxygen given off, compared with that 
>f the carbonic acid taken in, by the leaves of different plants. 

But at the same time the nitrogen is set i^ree. This nitrogen will 
either be again compounded in the plant with other elements, or, if not 
•equired for its healthy growth — that is, if more largely present than is 
•equired by the plant — it will be directly emitted by the leaves, or sent 
lown wards and permitted to escape by the root. Hence the reason 
^hy pure nitrogen is evolved from the leaves of some plants (p. 95), 
ind why ammonia exercises a beneficial action upon vegetation, in 
;ases where all the nitrogen it contains is neither retained nor required 
)y the plant. 

Does this decomposition necessarily require the agency of light? 
May it not take place in the absence of the son ? 

I will mention one or two facts which seem to throw light upon this 
)oint. 

1°. Plants grow in the dark. Though feeble and blanched, ihey iii- 
jrease largely in bulk; they must, therefore, have the power of assimi- 
ating their food to a certain extent, independent of the sun's rays. 

2°. Several species of Poa, Plantago, Trift)lium arvense, Cheiran- 
hus, &c., become green in the perpetual darkness of mines (Hum- 
3oldt). 

3°. When a little hydrogen is mixed with the air, plants become 
greenish, even in the dark (Sennebier) ; and when exposed to the sun, 
:he green becomes unusually intense in such a mixture (Ingenhouss). 



166 MODIFYING EITECT OF CLIMATE. 

The immediate and visible eflfect of an application of ammonia, or of 
soot, or of any top-dressing containing ammonia, is to render the green 
colour much more intense, and in the darkest weather. It is therefore 
probable, I think, that the hydrogen of the ammonia contributes to this 
immediate etiect, and that the ammonia itself may be decomposed and 
its elements appropriated to the nourishment of the living vegetable, 
either by the unaided vital powers of the plant, or in the presence of a 
feeble light only. Like water, ammoma \s peculiarly liable to decom- 
position, not always of that perfect kind which, /or the sake of simplicity ^ 
I have endeavoured to explain in the present lecture, yet such as to ren- 
der the elements of which it consists available to the general nourish- 
ment of the plant. 

§ 7. Comparative influence of nitric acid and of ammonia in different 

climates. 

It follows, from what is above stated, that the beneficial influence of 
ammonia upon vegetation will be readily perceived in all climates in 
which plants are found to flourish. Its eflects will be greater and more 
rapid where the heat and light are more intense,^-only because by these 
agents the functions of all life are stimulated. 

Not so with the nitric acid in the nitrates. In the presence of organic 
compounds, that is, in the sap of the plant, it is less easily decomposed 
than ammonia. It requires the interference of more pfjwerful agents— 
of a higher temperature, or of more brilliant light, — and thus its efficacy 
upon vegetation will be more dependent upon season and climate. 

Now, we have seen that in tropical countries the nitrates are produced 
in the greatest abundance, and there the high temperature and the bril- 
liant sun should render them most useful to vegetation. Such is well 
known to be the case, and it may be regarded as one of those bountiful 
adaptations with which all nature is full — that in these warmer regions, 
the ammonia produced in the soil is first converted into nitric acid, that 
it may remain fixed ^ and that this acid again is decomposed by the same 
agents (light and heat), Avhen it enters tlie living plant, and is required 
to minister to its growth. On the other hand, it may no less be regarded 
as a wise provision, that in colder and more uncertain climates, where 
warm and brilliant summers are less to be depended upon, that com- ' 
pound of nitrogen (ammonia) should more abound, which is most easily 
decomposed in the living plant, which is fitted in comparative darkness 
to yield up its nitrogen, and by the hydrogen it contains, to compensate 
in some slight degree for the partial absence of the stm's rays. 

From these views, tlierefore, we should draw tins further practical 
conclusion — that in our climate, ammonia is sure to promote vegetation, 
and in every season, while the nitrates will produce their maximum effect, 
othei tilings being equal, in such only as have abundant warmth and 
sunsliine. [s this conclusion consistent with observation? Will it 
serve to explain any of tlie apparent failures which have occasionally 
been experienced in the employment of the nitrates? 

§ 8. Stimulating infi.uence of these compounds. 
There remains one other y)oint in regard to the eflTect of these two 
compounds upon vegetation, to which I would request your attention. 



STIMULATING INFLUENCE OP' NITRIC ACID AND OF AMMONIA. 167 

We have seen that the quantity of nitrogen contained in a crop raised 
by the aid of farra-3'ard manure, is very much greater than that which 
exists in the manure itself, and the views just exposed serve to indicate 
the sources from which the excess is derived. But suppose that upon 
two patches of ground, of equal (|uality, the one of which is manured 
and the other not, equal quantities of the same seed be sown, it is 
consistent with experience — that the crop reaped from the manured 
portion will not only contain more nitrogen than that reaped from the 
unmanured portion, but so much more as shall considerably exceed that 
contained in the manure itself. Thus suppose the crop raised from the 
unmanured land to contain 100 lbs. of nitrogen, and that the manure laid 
on the other portion contained 100 lbs. also, the crop which is reaped 
from this latter portion, in favourable seasons, will exceed, and probably 
very far exceed, 200 lbs. Hence the effect of the ammonia, &c., in the 
farm-yard manure, is not merely to yield its own nitrogen to the plant, 
but to enable it, in some way hitherto unexplained, to draw from other 
sources a larger portion of the same element than it would otherwise do. 
So also with the nitrates. If two equal portions of the same grass or 
corn-field, in early spring, be measured off, and one of them be top- 
dressed with nitrate of soda or with saltpetre, the weight of nitrogen con- 
tained in the crop of hay or corn reaped from the latter, will generally 
be found to exceed that contained in the crop from the former, by a 
quantity much greater than that which was present in the nitrate with 
which the land was dressed.* In addition, therefore, to the nitrogen di- 

* The following calculations illustrate the statement in the text:— Mr. Gray, of Dilston, 
[see Journal of Royal English Agricultural Society,] applied nitrate of soda to grass land in 
the proportion of 112 lbs. to the acre. 

The produce without nitrate amounted to 2 tons 81 stones 
with 112 lbs. of nitrate to 3 tons 146 stones 

Increase, 1 ton 65 stones, or 3150 lbs. 
And 3150 -^ 112 = 28 >^ lbs. the increase of hay from each pound of nitrate of soda.* But al- 
lowing this hay to contain only one per cent, of nitrogen, 28 lbs. will contain 4^ ounces of ni- 
trogen, which is nearly double the quantity actually present in the nitrate employed. 

Again, in the case of a crop of grain — Mr. Hyett applied nitrate of soda to a field of wheat, 
and compared the produce with that from an equal portion to which no top-dressing was 
applied. ' 

CORN. STRAW. 

Bush. pks. pts. Cwt. qrs. lbs. 

Nitrated 43 2 11 31 2 3 

Without nitrate . . 33 2 6 23 1 21 

Excess, 10 5 8 10 

Calculating the bushel of corn at 60 lbs., the excess of corn amounted to 600 lbs., containing 
24/^ per cent, or 147 lbs. of gluten and albumen. The nitrogen in these substances, when 
properly dried, is from 15 to 17 per cent If we suppose the gluten not to have been quite 
dry, and allow only 14 per cent, of nitrogen, 147 lbs. would contain 20 >^ lbs. of this element. 
But the nitrated corn contained 5 per cent, more gluten and albumen than the un-nitrated, 
which in 33 bushels (2000 lbs.) gives 100 lbs. of gluten in excess, containing 14 lbs. of nitrogen. 
And 8 cwt. ofstraw(900 lbs.) contained one-third of aper cent, of nitrogen, [Boussingault,] 
or in all 3 lbs. 

Therefore the quantity of nitrogen present in the nitrated crop above that in the un-nitrated 
was as follows : 

1°. In 600 lbs. of wheat at 24)^ percent, of gluten . ...... 20X lbs. Nitrogen. 

2°. In 2000 lbs. of wheat at 5 percent, of gluten contained in excess, 14 lbs. do. 
3°. In 900 lbs. of straw at one-third per cent 3 lbs. do. 

Total nitrogen =37)^ lbs. 

But the nitrogen in 1 cwt. of dry nitrate of soda, as already stated. Is only 19 lbs. or little 
[* Dry nitrate of soda contains about 16)4 per cent, of nitrogen, being 19 lbs. to the cwt., 
or two and three-fifth ounces to the pound ; but as it is usually applied, it contains from 5 to 
10 per cent, of water. The nitrogen, therefore, may be estimated at 2)4 ounces in the pound. ] 



168 HOW THIS INFLUENCE IS MANIFESTED. 

rectly conveyed lo the plant by these nitrates, they also exercise some 
other influence, by which they enable tlie Uving vegetable to draw from 
natural sources a much larger supply ihan they would otherwise be 
capable of doing. What is this influence, and how is it explained ? 

This I suppose to be that kind of influence to which writers on agri- 
culture are in the habit of alluding, when they speak of certain substan- 
ces stimulating plants, or acting as stimulants to their growth, though the 
term itself conveys to the mind no distinct idea of the mode of operation 
intended to be indicated — of the way in which the effect is produced. 

In the present case, this special action of ammonia and the nitrates, 
and perhaps also of immediate applications of manure in general, ap- 
pears to arise from their affording to the plant, in its early youth, a copi- 
ous supply of nitrogenous food, by which it is enabled at once to shoot 
out in a more healthy and vigorous manner. It thrusts forth roots in 
greater numbers, and to greater distances, and is thus enabled to extract 
nourishment from a greater extent and depth of soil than is ever reached 
by the sickly plant — it expands larger and more numerous leaves, and 
thus can extract from the air more of every thing it contains which is 
fitted to supply the wants of the living vegetable ; as the stout and 
healthy savage can hunt and fish to support many lives, while the feeble 
or sickly can scarcely secure sustenance for himself alone. Feed a wild 
animal well the first few months of its life, and you may set it loose to 
prey for itself; starve it in its infancy, and its growth and strength will 
be stunted, and it may lead a wretched and hungry life. 

Even in soils, then, and situations, which are capable of yielding to 
the plant every thing it may require for its ordinary growth, it is an im- 
portant object of the art of husbandry to discover what substances are 
especially necessary or grateful lo particular crops, and to apply these 
directly, and in abundance, to the new-born plant, — in order that it may 
acquire suflftcient strength to be able to avail itself in the greatest degree 
of the stores of food which lie within its reach. 

Concluding observations regarding the organic constituents of plants. 

We have now considered the most important of those questions con- 
nected with the organic elements of plants, which are directly interesting 
lo the practical agriculturist. We have seen — 

1°. That all vegetable productions consist of two parts— one the or- 
ganic part, which is capable of being burned away in the air — the other, 
the inorganic part, which remains behind in the form of ash. 

2°. That this organic part consists of carbon, hydrogen, oxygen, and 
nitrogen only. 

3°. That plants derive the greater part of their carbon from carbonic 
acid, of their hydrogen and oxygen from water, and of their nitrogen 
from ammonia and nitric acid. 

4*^. That by far the largest portion of those substances which form 
the principal mass of plants, such as starch and woody fibre, consists of 
carbon united to oxygen and hydrogen in the proportions in which they 

more than half the quantity, which in consequence of the presence and action of the nitrate 
the wheat was enabled to obtain and appropriate above the quantity appropriated by the 
wheat in the un-nitrated part of the field. 

It requires no further proof, therefore, to show that the nitrate of soda and the nitrates must 
act insome other way in reference to vegetation, than by simply supplying aportion of nitrogen. 



CONCLUDING OBSERVATIONS. 169 

exist in water,— or, in other words, may be represented by carbon and 
water in various proportions. 

5°. That the food on which they live enters by the roots and leaves 
of plants, — that the leaves, under the influence of the sun, decompose 
the carbonic acid, give off its oxygen, and retain its carbon, — and that 
this carbon, uniting with the elements of water in the sap, forms those 
several compounds of which plants chiefly consist. 

6°. That the supply of carbonic acid in the atmosphere is kept up 
partly by the respiration of animals, partly by the natural decay of dead 
vegetable matter, and partly by combustion. That ammonia is sup- 
plied to plants chiefly by the natural decay of animal and vegetable 
substances — and nitric acid partly by the natural oxidation of dead or- 
ganic matter, and partly by the direct union of oxygen and nitrogen, 
through the agency of the atmospheric electricity. 

7°. That while both of these compounds yield nitrogen to plants, they 
each exhibit a special action on vegetable life, in virtue of the hydrogen 
and oxygen they respectively contain — and exercise also a so-called 
stimulating power, by which plants are induced or enabled to appro- 
priate to themselves, from other natural sources, a larger portion of 
all their constituent elements than they could otherwise obtain or 
assimilate. 

In illustrating these several points, it has been necessary to enter oc- 
casionally into details which, to those who have heard or may read only 
the later lectures, may not be altogether intelligible. I am not aware, 
however, of having introduced any thing of which the full sense will 
not appear on a reference to the statement by which it is preceded. 

We are now to consider the inorganic constituents of plants, — their na- 
ture, — the source (the soil) from which they are derived, — their uses in 
the vegetable and animal economy, — how the supply of these substan- 
ces is kept up in nature, — and how, in practical husbandry, the want of 
them may be at once efficaciously and economically supplied by art. 
This division of our subject, though requiring a previous knowledge of the 
principles discussed in the foregoing lectures, will be more essentially 
of a practical nature, and will lead us to consider and illustrate the 
great leading principle by which the practical agriculturist ought to be 
guided in the cultivation and improvement of his land. 

We shall here also find much light thrown upon our path by the 
results of geological inquiry ; and it is in the considerations I am now 
about to bring before you, that I shall have to direct your attention most 
especially to the principal applications of Geology to Agriculture. 



m 



1 



LECTURES 



ON THE 



APPLICATIONS OF CHEMISTRY AND GEOLOGY 



TO 



AGRICULTURE. 

ON THE INORGANIC ELEMENTS OF PLANTS. 



I 



CONTENTS OF PART II. 



LECTURE IX. 

INORGANIC CONSTITUENTS OF VEGETABLE SUBSTANCES. 



Of the relative propoi'tions of inorganic 

matter in vegetable substances. p. 178 

Kind of inorganic matter found iii plants. . 180 
Of the several elementary bodies usually 
met vfith in the ash of plants 182 



Of those compounds of the inorganic ele- 
ments which enter directly into the 
circulation, or exist in the substance 
and ash of plants 133 



LECTURE X. 

INORGANIC CONSTITUENTS OF PLANTS CONTINUED. 

To what extent do the crops most usual- 
ly cultivated exhaust the soil of inor- 
ganic vegetable food? 220 

Of the alleged constancy of the inorganic 
constituents of plants, in kind and 
quantity '225 



Inorganic constituents of plants continued. 200 
Tabular view of the constitution of the 
compounds of the inorganic elements 

above described 214 

On the relative proportions of the differ- 
ent inorganic compounds present in 
the ash of plants 216 



LECTURE XL 

NATURE AND ORIGIN OF SOILS. 



Of the organic matter in the soil 229 

General constitution of the eartliy part of 

the soil 230 

Of the classification of soils from their 

chemical constituents 232 

Of the distinguishing characters of soils 

and subsoils , 235 

Of the general origin of soils 236 



On the general structure of the earth's 
crust ..237 

Relative positions and peculiar charac- 
ters of tlie several strata 239 

Classification of the stratified rocks, their 
extent, and the agricultural relations of 
the soils derived from them 241 



LECTURE XIL 

COMPOSITION OF THE GRANITIC ROCKS, AND OF THEIR CONSTITUENT MINERALS. 



Composition of the granitic rocks 257 

Of the degradation of the granitic rocks, 

and of the soils formed from them ... .260 
Of the trap rocks, and the soils formed 

from them 263 

Of superficial accumulations of foreign 

materials, and of the means by which 

they have been transported 266 



Of the occurrence of such accumulations 
in Great Britain, and of their influence 
in modifying the character of the soil.. 270 

How far these accumulations of drift in- 
terfere with the general deductions of 
Agricultural Geology 272 

Of superficial accumulations of peat 275 



LECTURE XIII. 



EXACT CHEMICAL CONSTITUTION OF SOILS. 

Of tlie exact chemical constitution of 
certain soils, and of the results to be 

deduced from them 282 

Of the physical properties of soils 290 

Conclusion 297 



Of the exact nature of the organic con- 
stituents of soils, and of the mode of 
separating them.. . 277 

Of the exact chemical constitution of 
the earthy part of the soil.. 281 



177 



LECTURE IX. 

Inorganic c6nstituents of vegetable substances. — Relative proportions of organic and inor- 
ganic matter in plants. — Unlike proportions in unlike species. — Kind of inorganic matter 
which exists in different species. — Nature and properties of the several inorganic elemen* 
tary bodies found in plants. 

The consideration of the inorganic constituents of plants is no less 
important to the art of culture than the study of their organic elements, 
which has engaged our sole attention in the preceding part of these lec- 
tures. 

It has already been shown that when vegetable substances are heated 
to redness in the air, the whole of the so-called organic elements — car- 
bon, hydrogen, oxygen, and nitrogen — are burned away and disappear ; 
while there remains behind a fixed portion, commonly called the ash, 
which does not burn, and which in most cases undergoes no diminution 
when exposed to a red heat. This ash constitutes the inorganic portion 
of plants. 

The organic or combustible part of plants constitutes, in general, 
from 88 to 99 per cent, of their whole weight, even after they are dried. 
Hence the quantity of ash left by vegetable substances in the green 
state is often exceedingly small. It therefore long appeared to many, 
that the inorganic matter could be of no essential or vital consequence 
to the plant — that being, without doubt, derived from the soil, it was 
only accidentally present, — and that it might or might not be contained 
in the juices and solid parts of the living vegetable, without materially 
affecting either its growth or its luxuriance. 

Were this the case, however, the quantity and quality of the ash left by 
the same plant should vary with the soil in which it grew. If one soil 
contained much lime, another much magnesia, and a third much potash, 
whatever plant was grown upon these several soils should also contain 
in greatest abundance the lime, the magnesia, or the potash, which 
abounded in each locality — and the nature, at least, of the ash, if not 
its proportion, should be nearly the same in every kind of plant which 
is grown upon the same soil. 

Careful and repeated experiments, however, have shown — 

1°. That on whatever soil a plant is grown, if it shoots up in a 
healthy manner and fairly ripens its seed, the quantity and quality of 
the ash is nearly the same ; and 

2°. That though grown on the same soil, the quantity and quality of 
the ash left by no two species of plants is the same — and that the ash 
differs the more widely in these respects, the more remote the natural 
affinities of the several plants from which it may have been derived. 

Hence there is no longer any doubt that the inorganic constituents 
contained in the ash are really essential parts of the substance of plants, 
— that they cannot live a healthy life or perfect all their parts without 
them, — and that it is as much the duty of the husbandman to supply 
these inorganic substances when they are wanting in the soil, as it has 
always been considered his peculiar care to place within the reach of 



178 



WEIGHTS OF ASH LEFT BT DIFFERENT SPECIES. 



the growing plant those decaying vegetable matters which are most 
likely to supply it with organic food. 

For the full establishment of this fact, we are indebted to Sprengel. : 
Others, as De Saussure, have published many important and very use- 
ful analyses of the inorganic matters left by plants, but for the illustra- 
tion of the important practical bearing of this knowledge of their inor- 
ganic constituents on the ordinary processes of agriculture, we are, I 
beheve, in a great measure indebted to the writings and numerous ana- 
lytical researches of Sprengel. 

It is difficult to conceive the extent to which the admission of the es- 
sential nature and constant quality of the inorganic matter contained in 
plants, must necessarily modify our notions and regulate our practice in 
every branch of agriculture. It establishes a clear relation between the 
kind and quality of the crop, and the nature and chemical composition 
of the soil in which it grows — it demonstrates what soils ought to con- 
tain, and, therefore, how they are to be improved— it explains the effect 
of some manures in permanently fertilizing, and of some crops in per- 
manently impoverishing the soil — it illustrates the action of rnineral 
substances upon the plant, and shows how it may be, and really is, in a 
certain measure, /6^ by the dead earth : — over nearly all the operations 
of agricuUure, indeed, it throws a new and unexpected light. Of this, I 
am confident, you will be fully satisfied when I shall have discussed the 
various topics I am to bring before you in the present part of my lectures. 

§ 1. Of the relative proportions of inorganic matter in different 
vegetable substances. 
As above stated, the inorganic matter contained in different vegetable 
productions varies from 1 to 12 per cent, of their whole weight. The 
following table exhibits the weight of ash left by 100 lbs. of the more 
commonly cultivated plants — according to the analyses of Sprengel 
[Ckemie, vol. ii., passim] : — 



Grain of Per ct. 

Wheat . . 1-18 lbs. 
Rye . . . 1-04 
Barley . . 2-35 
Do. dried at 212, 2-52 J. 
Oats . . . 2-58 
Field Beans . 2-14 
Peas . 2-46 



Dry straw of 
Wheat 
Oats 
Barley 
Rye 
Beans 
Peas 



Perct. 
3-51 lbs. 
•74 
•24 
•79 
•12 
•97 



Potato . . . 
Turnip ... 
Do. white . 
Carrot . . 
Parsnip . . . 
Leaf of Potato 

Turnip . 

do. white 

Carrot 

Parsnip . 

Cabbage 



Undried. Dried in air. ' 
0^83 lbs. 2-65 lbs. 



0-63 
0^8 J. 
©•66 
0^82 

1-8 

2-18 J. 
1^98 
3^00 
0-53 



7^05 



09 
34 
79 
91 



10-42 

15-76 

7-5.5 



Lucerne 
Red Clover 
Whhe Clover 
Rye Grass . 



Green. 
2-58 lbs. 
1-57 
1^74 
1-69 



In hay. 
9^55 lbs 
7-48 
9-13 
5-3 



• Of the substances in this column the potato lost by drying in the air 69 per ct. of water, 
the turnip 91, the carrot 87, the turnip leaf 86, the carrot leaf, the parenip, and the parsnip 
leaf, each 81, and the cabbage leaf 93 per cent. 



IT VARIES WITH THE SPECIES OF PLANTS. 179 

In the parts of trees dried in the air there are found of inorganic 
matter — 

Wood. Leaves. Wood. Leaves. 



In the Elm . . 1-88 11-8 

Willow . 0-45 8-23 

Poplar . . 1-97 9-22 

Beech . . 0-36 6-69 



In the Oak . . 0-21 4-5 

Birch . . 0-34 5-0 

Pitch pine 0-25 3-15 

Comm. furze 0-82 3-1 J. 



In looking at the preceding tables, you cannot fail to be struck with 
one or two points, which they place in a very clear light. 

1°. That the quantity of inorganic matter contained in the same 
weight of the different crops we raise, or of the different kinds of vegeta- 
ble food we eat, or with which our cattle are fed, is very unlike. Thus 
100 lbs. of barley, or oats, or peas, contain twice as much inorganic 
(earthy and saline matter, that is,) as an equal weight of wheat or rye— 
and the same is the case with lucerne and while clover hays, compared 
with the hay of rye grass. 

2°. The quantity contained in different parts of the same plant is 
equally unlike. Thus 100 lbs. of the grain of wheat leave only ]|lbs. 
I of ash, while 100 lbs. of wheat straw leave 3|lbs. So the dry bulb of 
the turnip gives only 7 per cent., while the dry leaf leaves 13 per cent, 
of ash when it is burned. The dry leaves of the parsnip also contain 
nearly 16 per cent., though in its root, when sliced and dried in the air, 
there are only 4i per cent, of inorganic matter. 

In trees the same fact is observed. The wood of the elm contains 
less than 2 per cent., while its leaves contain nearly 12 per cent. ; — the 
wood of the oak leaves only ^ih of a per cent., while from its leaves 4i 
per cent, or 22 times as much are obtained. The leaves of the willow 
and of the beech also contain about twenty times as much as the wood 
of these trees does, when it has been dried under the same conditions. 

These differences cannot be the result of accident. They are con- 
stant on every soil, and in every climate ; they must, therefore, have 
their origin in some natural law. Plants of different species must 
draw from the soil that proportion of inorganic matter which is adapted 
to the constitution, and is fitted to supply the wants of each ; — while of 
that which has been admitted by the roots into the general circulation 
of the plant, so much must proceed to and be appropriated by each part 
as is suited to the functions it is destined to discharge. And as from 
the same soil different plants select different quantities of saline and 
earthy matter, so from the same common sap do the bark, the leaf, the 
wood, and the seed, select and retain that proportion which the healthy 
growth and developement of each requires. It is with the inorganic, as 
with the organic food of plants. Some draw more from the soil, some 
less, and of that which circulates in the sap, only a small portion is ex- 
pended in the production of the flower, though much is employed in 
forming the stem and the leaves. On the subject of the present section, 
I shall add two other observations. 

1°. From the constant presence of this inorganic matter in plants, and 
from its being always found in nearly the same proportion in the same 
species of plants,— a doubt can hardly remain that it is an essential pan 
of their substance, and that they cannot live and thrive without it. But 
that it really is so, is placed beyond a doubt, by the further experimen- 



180 QUALITY OF THE ASH FROM DIFFERENT PLANTS. 

tal fact, that if a healthy young plant he placed in circumstances where 
it cannot obtain this inorganic matter, it droops, pines, and dies. 

2°. But if it be really essential to their growth, this inorganic matter 
must be considered as part of the food of plants ; and we may as cor- 
rectly speak of feeding or supplying food to plants, when we add earthy 
and mineral substances to the soil, as when we mix with it a supply of 
rich compost, or of well fermented farm-yard manure. 

I introduce this observation for the purpose of correcting an erroneous 
impression entertained by many practical men in regard to the way in 
which mineral substances act when applied to the soil. By the term 
manure they generally designate such substances as they believe to be 
capable o^ feeding the plant, and hence reject mineral substances, such 
as gypsum, nitrate of soda, and generally lime, from the list of manures 
properly so called. And as the influence of these substances on vegeta- 
tion is undisputed, they are not unfrequently considered as stimulants only. 

Yet if, as I believe, the use of a wrong term is often connected 
with the prevalence of a wrong opinion^ and may lead to grave errors 
in practice, — I may be permitted to press upon your consideration 
the fact above stated — I may almost say demonstrated — that plants 
do feed upon dead unorganized mineral matter, and that you are, there- 
fore, really manuring your soil, and permanently improving it, when 
you add to it such substances of a proper kind. 

^2. Of the kind of inorganic matter found in plants. 

I have said above, of a proper kind — for it is not a matter of indiffer- 
ence to a plant, what kind of earthy or saline matter it takes in by its 
roots. Each species of plant, we have seen, withdraws from the soil a 
quantity of inorganic matter, which is peculiar to itself, and which, as a 
whole, is nearly constant. 

So also each species, in selecting for itself a nearly constant weight 
of inorganic matter, while it chooses generally the same kind of saline 
and earthy ingredients as other plants do, to make up this weight, yet 
picks them out in proportions peculiar to itself. Thus for example, lime 
is present in the ash of nearly all plants, but while 100 lbs. of the ash 
of wheat contain 8 pounds of lime, the same weight of the ash of barley 
contains only 4| lbs. So also potash is contained in the ash of most 
plants grown for food, but in the ash of the turnip, there are 37| per 
cent, of potash, while in that of wheat there are only 19 per cent. Again, 
in different parts of the same plants a like difference prevails. The ash 
of the turnip bulb contains 16i percent, of soda, — that of the leaf, little 
more than 12 per cent. On the other hand, the lime in that from the 
bulb constitutes less than 12 per cent, of its weight, while in that of the 
leaf it amounts to upwards of 34 per cent. 

These relative proportions among the different kinds of inorganic mat- 
ter contained in the ash of plants — like the whole weight itself of the 
ash — is nearly constant in the same species, and in the same part of a 
plant, when it is grown in a propitious soil. It is not, therefore, as I have 
already said, a matter of indifference to the living vegetable, whether 
it meets with this or with that kind of inorganic matter in the land on 
which it grows — whether its roots are supplied with lime, or with potash, 
or with soda. The soil must contain all these substances^ and in such 



m 



THE SOIL MUST CONTAIN WHAT THE PLANT REqUIRKS. 181 

quantity as easily to yield to the crop so much of each as the Icind of plant 
specially requires. And if one of these necessary inorganic forms of 
matter be rare or wholly absent, the crop will as certainly prove sickly 
or entirely fail, as if the organic food supplied by the vegetable matter 
of the soil were wholly withdrawn. It is, therefore, as much the end of 
an enlightened agricultural practice to provide for the various require- 
ments of each crop in regard to inorganic food, as it is to endeavour to 
enrich the land with purely vegetable substances. -^ 

Since, also, as above shown, not only the relative quantity of inor- 
ganic matter, but its kind or quality, likewise, is different in different 
plants, — it may be, that a soil on which one crop cannot attain to ma- 
turity may yet surely and comi)letely ripen another — a fact which is 
proved by every-day experience. The soil, which is unable to supply 
with sufficient speed all the lime or the potash required for one crop, 
may yet easily meet the demands of another, and afford an ample re- 
turn to the husbandman when the time of harvest comes.* 

On the other hand, this consoling, at once, and stimulating reflection 
must arise in the mind of the practical agriculturist from the considera- 
tion of the above facts — that if the soil contain all the inorganic substan- 
ces required by plants, and in sufficient quantity, it will grow, if rightly 
tilled, any crop which is suited to the climate, — or conversely to make 
it capable of growing any crop, he has only — along with his usual sup- 
plies of animal or vegetable matter — to add in proper quantity these in- 
organic substances also. 

Here a crowd of questions cannot fail to start up in your minds. You 
will ask, for example, 

1°. What are the several inorganic substances usually present in 
cultivated plants, and what their respective proportions ? 

2°. Which of them are most generally present in the soil? 

3°. In what form can those which are less abundant be added most 
easily, most advantageously, and most economically ? 

We shall consider in succession these, and along with them other 

* On the same principle, also, some of the interesting facts connected with the grafting of 
trees are susceptible of a satisfactory explanation. 

The root of a tree selects from the soil tlie kind and jwaiiYy of inorganic matter which 
are required for the healthy maturity of its own parts. Any other tree may be grafted on it, 
which in its natural state requires the same kind of inorganic matters in nearly the same 
proportion. This is the case generally wi(h varieties of the same species — more rarely 
with trees or plants of different species — and least frequently with such as belong to differ- 
ent genera. The lemon may be grafted on the orange, because the sap of the latter con- 
tains all the earthy and saline substances which the former requires, and can supply them 
in sufficient quantity to the engrafted twig. But the fig or the grape would not flourish or 
ripen fruit on the same stock — because these fruits require other substances than the root of 
the orange cares to extract from the soil, or in greater quantity than the sap of the orange 
can supply them. 

It is not for want of organic food, for of this the sap of nearly all plants is full — and we 
have seen in our previous lectures, how the sugar of the fig, the tartaric acid of the grape, 
and the citric acid of the lemon, may all be produced by natural processes from the same 
common organic food. When we plant a tree or sow a crop on a soil which does not con- 
tain all that the tree or crop requires, the tree must slowly perish, — the crop cannot yield a 
profitable return. So It is in grafting. TTie sajj of the stock must contain all that Ifie engrafted 
bud or shoot requires in every stage of its growth. Or to recur to our former illustration — 
if the potash or lime required by the grape be not taken up and in sufficient quantity by 
the root of the orange, it will be in vain to graft the former upon the latter with the hope of 
its coming to maturity or yielding perfect fruit. 

Tills principle may also serve to explain many other curious and hitheito obscure cir- 
cumstances connected with the practice of the gardener. 

16 



182 



ELEMENTARY SUBSTANCES FORMED IN THE AS». 



subsidiary questions, which will hereafter present themselves to our 

notice. 

§■ 3. Of the sev6ral elementary bodies usually met ivith in the ash ef plants 

What is uiiderstood by the term element or elementary body among 
chemists has already been explained (Lect. I., p. 22), as well as the 
number and names of those elements with which we are at present ac- 
quainted. 

Of these elementary bodies we have seen that thai orga'nic part of pianis 
contains rarely more than four, namely, carbon, liydrogen, ojiygen, and 
nitrogen, in various proportions. In the inorganic part there occur nine 
or ten others, generally in combination, either with oxygen or with one 
another. 

The names of tliese inorganic elements are as'folk)W : 

Forming 

Chlorides. 
Iodides. 

SuLPHUREtS. 

Sulphuretted Hydrogen.*' 

Sulphuric Acid. 

Phosphoric Acid. 

Potash. 

Chloride of Potassium. 

Soda. 

Chloride of Sodium or 
Common Salt. 

Chloride op Calcium. 

Lime. 

Magnesia. 

Alumina. 

Silica. 
) Oxides. 
[ Sulphurets. 

Other elementary bodies, chiefly metallic, occur in some plants — occa- 
sionally, and in very small quantity,^—but, so far as is yet known, they do 
not appear to be either necessary to their growth, or to exercise any ma- 
terial influence on the general vegetation of the globe. 

Of all the above elementary bodies it may be said, generally, 

1°. That with the exception of sulphur,f they are not known to exist 
or to be evolved, in any quantity, anywhere on the surface of the globe, 
in their simple, elementary, or uncombined state; and that, therefore, 
in this state they in no way affect the progress of vegetable growth, or 
require to occupy the attention of the practical agriculturist. 

2°. They all, however, exist in nature more or less abundantly in a 
state of combination with other substances, and chiefly with oxygen, [for 
an explanation of the meaning and of the laws of chemical combination,- 
see Lecture II., p. 32] — but in no state of combination are they known 
to be generally diffused through the atmosphere of the globe, so as to be 

* Called also Hydro-sulphuric Acid. 

t Given oflfin vapour from active volcanoes, and from rents and fissures 'n ancient volcartic* 
countries. j 



Name. In 


combination wit 


Chlorine . 


Metals 


Iodine . . 


do. 


Sulphur . 


do. 




Hydrogen 




Oxvgen 


Phosphorus 


do. 


POTASSIIJM . 


do. 




Chlorine 


Sodium . . 


Oxygen 




Chlorine 


Calcium . 


do. 




Oxygen 


Magnesium 


do. 


Aluminium 


do. 


Silicon 


do. 


Iron and ) 


do. 


Manganese ^ 


Sulphur 



I 



CHLORrXE A^V MURIATIC ACID. 183 

capable of entering plants by tbeir leaves or other superior parts. They 
must all, therefore, enter by ihe roots of plants, — must consequently ex- 
ist in the land, — and must all be necessary constituents of that soil in 
which the plants that contain them grow. 

It will not be necessary, therefore, to consider so much the relative 
proportions in which these elementary bodies themselves exist in plants, 
as that of the several chemical compounds which they form with oxy- 
gen, or with one another — in which states of combination they exist in 
the soil, and are found in the circulation and substance of the plant. As 
a preliminary to this inquiry, however, it will be proper to lay before 
you a brief outline of the nature and properties of tliese compound 
bodies themselves — and of the direct influence they have been found to 
exercise upon vegetable life. 

§ 4. Of those compounds of the inorganic elements lahich enter directly into 
the circulation, or exist in the substance and ash of plants. 

I CHLORINE AND MURIATIC ACID. 

CJilorine. — If a mixture of common salt and black oxide of manga- 
nese [sold by this name in the shops] be put into a flask or bottle of 
colourless glass, and sulphuric acid (oil of vitriol) be poured upon it» a 
gas of a greenish-yellow colour will be given off', and will gradually fill 
the bottle. This gas is distinguished by the name oC chlorine. 

It is readily distinguished from all other substances by its greenish- 
yellow colour, and its pungent disagreeable smell. It extinguishes a 
lighted taper, but phosphorus, gold leaf, metallic potassium and sodium, 
and many other metals, take fire in it and burn of their own accord. It 
is nearly 4i times heavier than common air, and therefore may be 
readily poured from one vessel to another. Water absorbs twice its 
own bulk of the gas, acquiring its colour, smell, and disagreeable astrin- 
gent taste. 

Animals cannot breathe it without suffocation — and, when unmixed 
with air, it speedily kills all living vegetables. The solution of chlorine 
in water was found by Davy to promote the germination of seeds. 

It does not exist, and is rarely evolved, [see Lecture V., p. 94,] in 
nature in a free or uncombined state, and therefore is not known to ex- 
ercise any direct action upon the general vegetation of the globe. It 
exists largely, however, in common salt (chloride of sodium), every 100 
lbs. of this substance containing upwards of 60 lbs. of chlorine. Indi- 
rectly, therefore, it may be supposed to influence, in some degree, the 
growth of plants, where common salt exists naturally in the soil, or is 
artificially applied in any form to the land. 

Murialic acid^ the spirit of salt of the shops, consists of chlorine in 
combination with hydrogen. It is a gas at the ordinary temperature of 
the atmosphere, but water absorbs between 400 and 500 times its balk 
of it, and the acid of the shops is such a solution in water, of greater or 
less strength. 

Muriatic acid has an exceedingly sour taste, corrodes the skin, and in 
its undiluted state is poisonous both to animals and plants. It dissolves 
common pearl ash, soda, magnesia, and limestone, with effervescence ; 
and readily dissolves also, and combines with, many earthy substances 
which are contained in the soil. 



184 IODINE, SULPHUR, AND SULPHUROUS ACID. 

When applied lo living vegetables in the state of an exceedingly di- 
lute solution in water, it has been supposed upon some soils, and in 
some circumstances, to be favourable to vegetation. Long experience, 
hovi^ever, on the banks of the Tyne, and elsewhere, in the neighbour- 
hood of the so-called alkali* works, has proved that in the state of va- 
pour its repeated application, even when diluted with much air, is in 
many cases fatal to vegetable life. 

Poured in a liquid stale upon fallow land, or land preparing for a 
crop, it may assist the growth of the future grain, by previously forming, 
with the ingredients of the soil, some of those compounds which have 
been occasionally applied as manures, and which we shall consider 
hereafter. 

Chlorine is represented by CI, and muriatic acid by HCl. 

II. IODINE. 

Iodine is a solid substance of a lead grey colour, which, when heated, 
is converted into a beautiful violet vapour. It exists in combination 
chiefly with sodium, as Iodide of Sodium, in sea water and in marine 
plants ; but it has not hitherto been detected in any of the crops usually 
raised for food. 

Like chlorine, it is poisonous both to animals and plants; and was 
found by Davy to assist and hasten germination. It may possibly exert 
some hitherto unobserved influence upon vegetation, when it is applied 
to the soil in districts where sea-ware is largely collected and employed 
as a manure. 

Iodine is slightly soluble in water, and this solution has been men- 
tioned in a previous lecture (VL, p. 107), as affording a ready means 
of detecting starch by the beautiful blue colour it gives with this sub- 
stance. 

III. SULPHUR, SULPHUROUS AND SULPHURIC ACIDS, AND SUL- 
PHURETTED HYDROGEN. 

1°. Sulphur is a substance too well known to require any detailed 
description. In an uncombined state it occurs chiefly in volcanic coun- 
tries, but it may sometimes be observed in the form of a thin pellicle on 
the surface of stagnant waters— or of mineral springs, which are natu- 
rally charged with sul{)hurous vapours. In this slate it is not known 
materially to influence the natural vegetation in any part of the globe. 
It has, however, been employed with some advantage in Germany as a 
top-dressing for clover and other crops to which gypsum in that country 
is generally applied. The mode in which it may be supposed to act 
will be considered hereafter.* 

2°. Sulphurous acid. — When sulphur is burned in the air it gives off 
a gaseous substance in the formof white fumes of a well known intensely 
suffocating odour. These fumes consist of a combination of the sulphur 

• In these works carbonate of soda (the common soda of the shops) and sulphate of soda 
(glauber salt) are manufactured from common salt, and in one of the processes immense 
quantities of muriatic acid are given off from the furnace, and used to escape into the air by 
tne chimney. 

t The refuse heaps of the alkali works on the Tyne contain much sulphur and more gyp- 
sum — but the farmers, perhaps, naturally enough, consider that if the works themselves do 
harm to their crops, the refuse of the works cannot do them much good. There are thou- 
sands of tons of this mixture which may be had for the leading away. 



SULPHURIC ACID, AND SULPHURETTED HYDROGEN. 185 

which disappears with the oxygen of the atmosphere, and are known 
to chemists by the name of sulphurous acid. This compound is des- 
tructive to animal and vegetable life, but as it is not known to be directly 
formed to any extent in nature, except in the neighbourhood of active 
volcanoes, it probably exercises no extensive influence on the general 
vegetation of the globe. 

This gas possesses the curious property of bleaching many animal and 
A'egetable substances. Wool and straw for plaiting are bleached to an 
almost perfect whiteness — when they are suspended in a vessel or room 
into which a plate of burning sulphur has been introduced. Gardeners 
sometimes amuse themselves also in bleaching roses and other red 
flowers, by holding them over a burning sulphur match. Some shades of 
red resist this action more or less perfectly, and the colour of the bleached 
flowers may often be restored — by dipping them in a dilute solution of 
carbonate of soda, or by holding them over a bottle of hartshorn (liquid 
ammonia). 

3. Sulphuric acid. — This is the name by which chemists distinguish 
the oil of vitriol of the shops. It is also a compound of sulphur and oxy- 
gen only, and is formed by causing the fumes of sulphur to pass into 
large leaden chambers along with certain other substances, from which 
they can obtain a further supply of oxygen. 

It is met with in the shops in the form of an exceedingly sour corrosive 
liquid, which decotTi poses, chars, and destroys all animal and vegetable 
substances, and, except when very diluted, is destructive to life in every 
form. It is rarely met with in nature, in an uncombined state, — though 
according to Boussingault, some of the streams which issue from the 
volcanic regions of the Andes are rendered sour by the presence of a 
quantity of this acid. 

It combines with potash, soda, lime, magnesia, &c., and forms sul- 
phates which exist abundantly in nature, and have often been benefi- 
cially and profitably employed as manures. 

Where the soil contains lime or magnesia, the acid may often be ap- 
plied directly to the land, in a very dilute state, with advantage to clover 
and other similar crops. It has in France, near Lyons, been observed 
to act favourably when used in this way, while in Germany it has been 
found better to apply it to the ploughed land, previous to sowing. A few 
experiments have also been made in this country with partial success. 
It is deserving, however, of a further trial, and in more varied circum- 
stances. 

4°. Sulphuretted Hydrogen. — This gaseous compound of sulphur 
with hydrogen, is almost universally known by its unpleasant smell. 
It imparts their peculiar taste and odour to sulphurous springs, such as 
that of Harrogate, and gives their disagreeable smell to rotten eggs. It 
is often produced in marshy and stagnant places,* and fish ponds, where 

* This appears to be especially the case on the coasts of Western Africa, where the 
hot sun is continually beating on sea water, often shallow, frequently stagnant, and always 
laden with organic matter, either animal or vegetable (Daniell). Near (he mouth of the 
Tees in this county, where a shallow, dark blue, muddy, samphire-bearing tract stretches 
for several miles inland from Seaton Snook, the presence of sulphuretted hydrogen may be 
perceived by the smell, when on a hot summer's day a gentle air skims along the edge of 
the Slake. The favourable conditions are, a burning sun, a very gentle air, and such a con- 
dition of the sea — that those parts and pools which are only reached by the spring Ude9| 
shall have been several days uncovered. 



186 PHOSPHORUS AND PHOSPHORIC ACID. 

vegetable matter is undergoing decay in the presence of water contain- 
ing gypsum, or other sulphates ; and it may occasionally be detected by 
the sease of smell among the roots of the sod, in old pasture land, to 
which a top-dressing is occasionally given. 

As in the egg, so also in other decaying animal substances, especially 
when the air is in some measure excluded, this gas is formed. In pu- 
trified cow's urine, and in night soil, it is present in considerable quan- 
tity. 

Sulphuretted hydrogen is exceedingly noxious to animal and vegeta- 
ble life, when diffused in any considerable quantity through the air by 
which they are «urrounded. The luxuriance of the vegetation in the 
neighbourhood of sulphurous springs, however, has given reason to be- 
lieve that water impregnated with this gas, may act in a beneficial 
manner when it is placed within reach of the roots of plants. It seems 
also to be ascertained that natural or artificial waters which have a sul- 
phurous taste, give birth to a peculiarly luxuriant vegetation, when they 
are employed in the irrigation of meadows. — [Sprengel, Chemie^ I., 
p. 355.] 

The relative constitution of these three compounds of sulphur is thus 
represented:— 





Is repre- 


Or 1 of Sulphur 


>ne equivalent of Weighing 


sented by 


and 


Sulphur ..... 46 


s 




Sulphurous Acid . . 32 


so^ 


2 of Oxygen 


Sulphuric Acid ... 40 


S03 


3 of Oxygen 


Sulphuretted Hydrogen 17 


SH 


1 of Hydrogen. 



I 



IV. PHOSPHORUS AND PHOSPHORIC ACID. 

1°. Phosphorus is a solid substance of a pale yellow colour, and of a 
consistence resembling that of wax. "When exposed to the air it slowly 
combines with the oxygen of the atmosphere, and burns away with a 
pale blue flame visible only in the dark. When rubbed, however, or 
exposed to a slight elevation of temperature, even to the heat of the 
hand, it readily bursts into a brilliant flame, emitting an intense light 
accompanied by dense white vapours. It does not occur in nature in. 
an uncombined state, and is not known to be susceptible of any useful 
application in practical agriculture. 

2°. Phosphoric Acid. — The white fumes given off' by phosphorus, or 
rather into which it is changed, when burned in the air or in oxygen 
gas, consist of phosphoric acid. This compound is solid and colourless, 
attracts moisture from the air with great rapidity, is exceedingly soluble 
in water, has an intensely sour taste, and like sulphuric acid is capable 
of corroding and destroying animal and vegetable substances. 

It does not exist in nature in a free state, and, therefore, is not directly 
influential upon vegetation. It unites, however, with potash, soda, lime, 
&;c., to form compounds, known by the name o^ phosphates. In these 
states of combination, it is almost universally diffused throughout nature 
— and appears to be essentially necessary to the healthy growth and 
maturity of all living — certainly of all cultivated vegetables. 

• For the properties of oxygen and hydrogen see above, pages 24 and 25, and for their 
equivalent or atomic weights see page 34. 



WOOD-ASH AND CARBONATE OF POTASH. 187 

v.— POTASSIUM, POTASH, CARBONATE, SULPHATE, OXALATE, TARTRATE, 
CITRATE, AND SULPHATE OF POTASH, AND CHLORIDE OF POTASSIUM. 

1°. Carbonate of Potash. — Tn countries where non-resinous trees 
abound, it is usual to burn the wood which cannot otherwise be employ- 
ed — as in the clearings in Canada and the United States — for the pur- 
pose of collecting the ash which remains. This ash is washed with 
water and the washings boiled to dryness in iron pots. In this state it 
forms the pot-ash of commerce. When this potash is again dissolved 
in water, and the clear liquid decanted and boiled, the pearl-ash of the 
shops is obtained. 

This pearl-ash is an impure form of the carbonate of potash of chem- 
ists. It readily dissolves in water, has a peculiar taste— distinguished 
as an alkaline taste — and dissolves in vinegar or in diluted sulphuric or 
muriatic acid, with much effervescence. The gas given off during this 
effervescence (or boiling up) is carbonic acid, the same which, as was 
shown in a previous lecture, is obtained when a diluted acid is poured 
upon chalk or common limestone. 

This carbonate of potash has been long known to exercise a powerful 
influence over the growth of plants. 

The use of wood-ash as a fertilizer both of pasture and of arable land, 
goes back to the most remote antiquity ; and though the crude wood-ash 
contains other substances also, yet much of its immediate and most ap- 
parent effect is due to the carbonate of potash it contains. 

From v/hat has already been stated, at the commencement of the 
present lecture, in regard to the presence of potash in the parts and 
juices of nearly all plants, you will already in some measure under- 
stand why the carbonate of potash should be useful to vegetation, and — 
since this alkali (potash) is present in greater quantity in some than in 
others — why it should appear to be more especially favourable to the 
growth of one kind of plant than of another. 

In this way, it is explained why moss and coarse grasses are extirpa- 
ted from meadows by a sprinkling of wood ashes — ^and why red clover, 
lucerne, esparsette, beans, peas, flax, and potatoes, <fec., are greatly 
promoted in their growth by a similar treatment. This substance, how- 
ever, has other functions to perform in reference to vegetation, besides 
that of simply supplying the crop with the potash it requires ; these func- 
tions I shall explain more particularly hereafter, when you will perhaps 
be better prepared for understanding the details into which it will be ne- 
cessary to enter. 

2°. Potash. — When 12 parts of carbonate of potash are dissolved in 
water, and boiled with half their weight of newly-slaked quick-lime, 
they are gradually deprived of their carbonic acid, and converted into 
pure potash, — or as it is often called, from its effect on animal and ve- 
getable substances, caustic potash. 

The caustic liquid thus obtained decomposes or dissolves most animal 
and vegetable substances, whether living or dead. When applied to 
the skin, unless it be in a very diluted state, it destroys it, and produces 
a painful sore. Potash does not occur in nature in this caustic or un- 
combined stale, and is not known, therefore, to exercise any direct in- 
fluence upon natural vegetatiori. 

When wood-ashes and quick-lime are mixed together in artificial 



188 POTASSIUM, CAUSTIC POTASH, AND CHLORIDE OF POTASSIUM. 

composts, it is not unlikely thai a portion of the carbonate of potash may 
be rendered caustic, and, therefore, be more fit lo act upon the vegetable 
matter in contact with it — by rendering it soluble in water and thus ca- 
pable of entering into the roots of plants. To this point I shall have 
occasion to return hereafter. In the mean time, it is proper to remark, 
that if pearl-ash be mixed, as above prescribed, with half its weight of 
quick-lime, and then boiled Avith less than ten or twelve times its weight 
ofivateYy a jmrt of the potash only is rendered caustic — the lime being 
unable to deprive the pearl-ash (carbonate of potash) of its carbonic 
acid, unless it be largely diluted. Hence, in dry composts, or mixtures 
of this substance with quick-lime, it is unlikely that any large portion of 
the potash can be at once brought lo the caustic state. This fact is 
really of importance in reference lo the theory of the conjoined action of 
quick-lime and wood or pearl-ash, when mixed together in artificial ma- 
nures, and applied to the land. 

3°. Potassium. — When dry caustic potash, obtained by evaporating 
the caustic solution above described, is mixed with powdered charcoal 
and iron filings, and exposed to an intense heat in an iron retort, it is de- 
composed, and metallic potassiuyn distils over, and is collected in the 
form of white shining silvery drops. 

It was one of the most remarkable discoveries of Sir H. Davy, that 
potash was a compound substance, and consisted of this metal potassium 
united to oxygen gas. 

Potassium is remarkable for the strong tendency it possesses to unite 
again with oxygen and re-form potash. When simply exposed to the 
air, it gradually absorbs oxygen from the atmosphere ; but if it be heat- 
ed in the air, it takes fire and burns. When the combustion has ceased» 
a quantity o^ caustic potash remains, the weight of which is nearly one- 
fifth greater than that of the potassium employed. It even bursts into a , 
flame when thrown upon water, depriving that liquid of iis oxygen, and | 
liberating its hydrogen, — and it was justly considered as the most aston- 
ishing property of this metal, when first discovered, that it took fire 
•when placed upon the coldest ice. [For the composition of water, see 
Lecture II., p. 36.] When thus burned in contact with water, potash 
is formed, as before, and is found dissolved in ihe liquid when the ex- 
periment is completed. 

4°. Chloride of Potassium. — This is a compound of chlorine with po- 
tassium, which, in taste, properties, and general appearance, has much 
resemblance to common salt. It may be formed by dissolving pearl- 
ash in dilute muriatic acid (spirit of salt) as long as any effervescence 
appears, and afterwards evaporating to dryness. It exists in small 
quantity in sea water, in the ash of most plants, and freqitently in the 
soil. It is not an article of manufacture, but is occasionally extracted 
from kelp, and sold to the alum makers. Could it be easily and cheap- 
ly obtained, there is no doubt that it might be employed with advantage 
as a manure, and especially in those circumstances in which common 
salt has been found to promote vegetation. The refuse of the soap-boil- 
ers, where soap is made from kelp, contains a considerable quantity of 
this compound. This refuse might be obtained at a cheap rate, and, 
therefore, might be usefully collected and applied to the land where 
such works are established. 



SULPHATE, NITRATE, OXALATES, AND CITRATES OF POTASH. 189 

5°- Sulphate of Potash.-^This compound is formed by adding pearl- 
ash to dilute sulphuric acid (oil of vitriol) as long as effervescence ap- 
pears, and then evaporating the solution. It is a white saline sub- 
stance, sparingly soluble in water, and has a disagreeable bitterish taste. 
£t exists in considerable quantity in wood-ash, and in the ash of nearly 
all plants, and is one of the most abundant impurities in the common 
potash and pearl-ash of the shops. This sulphate itself is not an article 
of e.Ktensive manufacture, but it exists in common alum to the amount 
of upwards of 18 per cent, of its weight. 

Dissolved in 100 times its weight of water, the sulphate of potash has 
been found to act favourably on red clover, vetches, beans, peas, <fec., 
and part of the effect of wood ashes on plants of this kind is to be attri- 
buted to the sulphate of potash they contain. Turf ashes are also said 
1.0 contain this salt in variable (juantity, and to this is .ascribed a portion 
of their efficacy also when applied to the land. 

6°. Nitrate of Potash, or saltpetre, is a well known saline substance, 
of which mention has already been made in the preceding lectures. [See 
p. 56, and pp. 159 to 1133.] It contains potash and nitric acid only, and 
may be readily formed by dissolving pearl-ash in nitric acid, and eva- 
porating the solution. It exists, and is continually reproduced in the 
soil of most countries, and is well known to exercise a remarkable influ- 
ence in accelerating and increasing the growth of plants. 

7°. Oxalates of Potash. — These salts exist in the common and wood 
sorrels, and in most of the other more perfect plants in which oxalic 
acid is known to exist. [See pp. 47 and 137.] The salt of sorrel is the 
best known of these oxalates. This salt has an agreeable acid taste, 
and is not so poisonous as the uncombined oxalic acid. 

When this salt is heated over a lamp, the oxalic acid it contains is de- 
composed, and carbonate of potash is obtained. It is supposed that a 
great part of the potash extracted from the ashes of wood and of the 
stems of plants in general, in the state of carbonate, existed as an oxa- 
late in the living tree, and was converted into carbonate during the com- 
bustion of the woody fibre and other organic matter. This compound, 
therefore, in all probability, performs an important part in the changes 
which take place in the interior of plants, though its direct agency in 
afTecting their growth when applied externally to their roots has not 
hitherto been distinctly recognized. It is probably formed occasionally 
in farm-yard manure, and in decaying urine and night-soil, but nothing 
very precise is yet known on this subject. 

8°. Citrates and Tartrates of Potash. — These salts exist in many 
fruits. The citrates abound in the orange, the lemon, and the lime — 
the tartrates in the grape. When heated over a lamp, they are decom- 
posed, and like the oxalates leave the potash in the state of carbonate. 

In the interior of plants, both potash and soda are most frequently 
combined with organic acids (oxalic, citric, tartaric, &c., for an ac- 
count of the most abundant of which see Lecture VI., p. 121,) and the 
compounds thus formed are generally what chemists call acid salts — 
that is to say, they generally have a distinctly sour taste, redden vege- 
table blues, and contain much more acid than is found to exist in cer- 
tain other well known compounds of the same acids with potash. 

The citrates and tartrates are not known to be formed in nature, ex- 



190 PHOSPHATES OF POTASH, AND CHLORIDE OF SODIUM. 

cept in the living plant, and as they are too expensive to be ever em- 
ployed as manures, it is the less to be regretted that few experiments 
have yet been tried with the view of ascertaining their effect upon vege- 
tation. 

9°. Phosphates of Potash. — If to a known weight of phosphoric acid 
(p. 186) pearl-ash (carbonate of ]M>tash) be added as long as any effer- 
vescence appears, and the solution be then evaporated, phosphate of 
potash is obtained. If to the solution before evapf)ration a second por- 
tion of phosphoric acid be added, ecjual to the first, and the water be 
then expelled by heat, Bi-phosphate of i^otash will remain, [so called 
from hiSy twice, because it contains ttvice as much acid as the former, or 
neutral phosphate.] 

One or other of these two salts is fonnd in the ash of nearly all plants. 
Whether or not the elements o^ which they consist exist in this state of 
combination in the living plant will be considered hereafter, in the mean 
lime it may be stated as certain that they are of the most vital impvr- 
tance not only in reference to the growth of plants themselves, but also 
to their nutritive qualities when eaien by animals for food. 

These phosphates are occasionally, i)erhaps very generally, present 
in the soil in minute quantities, and there is every reason to believe 
that could they be applied to the land in a sufficiently economical form, 
they would in many cases act in a most favourable manner upon vege- 
tation. They are contained in urine and other animal manures, and to 
their presence a portion of the efficacy of these manures is to be ascribed. 

VI. SODIUM, SODA, CARBONATE OF SODA, SULPHATE OF SODA, SULPHU- 

RET or SODIUM, CHLORIDE OF SODIUM. 

1°. Chloride of Sodium, common or sea salt, exists abundantly in sea 
water, and is found in many parts of the earth in the form either of in- 
crustations on the surface or of solid beds or masses at considerable depths. 
The rock salt of Cheshire is a well known example of this latter mode 
of occurrence. 

Common salt may also be detected in nearly all soils, it is found in 
the ashes of all plants, but especially and in large quantity in the ashes of 
marine plants (kelp), and is sometimes borne with the spray of the sea to 
great distances inland, when the winds blow strong, and the waves are 
high and broken. 

On some rocky shores, as on that between Berwick and Dunbar, the 
spray may be seen occasionally moving up the little coves and inlets in 
the form of a distinct mist driving before the wind, and the saline matter 
has been known to traverse nearly half the breadth of the island before 
it was entirely deposited from the air. 

It is impossible to calculate how much of the saline matterof sea water 
may in this way be spread over the surface of a sea-girt land like ours; 
but two things are certain — that those places which are nearer the sea 
will receive a greater, and those more inland a lesser, portion ; and that 
those coasts on which sea winds prevail will be more largely and more 
frequently visited than those on which land winds are more commonly 
experienced. 

It is well known that common salt has been employed in all ages and 
in all countries for the purpose of {)romoting vegetation, and in no coun- 



SULPHATE OF SODA, SULPHURET OF SODIUM, CARBONATE OF SODA. 191 

try perhajjs in larger quantity or more extensively than in England. 
That it has often failed to benefit ifie land in particular localities, only 
shows that the soil in those places already contained anatural supply of 
this compound large enough to meet the wants of the crops which grew 
upon it. The facts above stated as to the influence of the wind in top' 
dressing the exposed coast-line of a country with a solution of salt, may 
serve as an important guide both in reference to the places in which it 
may be expected to benefit tlie land, and to the causes of its failing to 
do so in particular districts. 

2°. Sulphate of Soda, or Glauber's salt, is usually manufactured from 
common salt by pouring upon it diluted suljihuric acid (oil of vitriol), 
and applying heat. Muriatic acid (spirit of salt, so called by the old 
chetnists, because thus given off by common salt,) is given off in the 
form of vapour, and sulphate of soda remains behind. It may also be 
prepared, though less economically, by adding the common soda of the 
shops to diluted sulphuric acid as long as any effervescence appears. 

This well known salt is met with in variable quantity in the ashes of 
nearly all plants, and is diffused in minute proportion through most 
soils. I have elsewhere [see Appendix,] directed your attention to the 
beneficial effect which it has been observed to exercise on the growth 
especially of such plants as are known to contain a considerable propor- 
tion of sulphuric acid. Among these are red clover, vetches, peas, &c. 
And as this salt is manufactured largely in this country, and can be ob- 
tained at the low price of ten shillings a cwt. in the dry state,* I have 
recommended it to the practical farmer as likely to be extensively useful 
as a manure for certain crops and on certain soils. The kind of crops 
and soils have as yet in great measure to be determined by practical 
trials. — [See the results of Mr. Fleming's Experiments, given in the 
Appendix.] 

3°. Suljihuret of Sodium. — When sulphate of soda is mixed with 
saw-dust, and heated in a furnace, the oxygen of the salt is separated, 
and sulphuret of sodium is produced. By a similar treatment sulphate 
of potash is converted into sulphuret of potassium. These compounds 
consist of sulphur and metallic sodium or potassium only. They do 
not occur extensively in nature, and are not manufactured for sale; but 
there is reason to believe that they would materially promote the vege- 
tation of such plants as contain much sulphur in combination with pot- 
ash or soda. The sulphuret of sodium is present in variable quantity in 
the refuse lime of the alkali works, already spoken of, and might be ex- 
pected to aid the other substances of which it chiefly consists, in contri- 
buting to the more rapid growth of pulse and clover crops. 

4°. Carbonate of Soda. — I have described the above compounds of 
soda before mentioning this its best known and most common form, be- 
cause they are all steps in the process by which the latter is usually pre- 
pared from common salt, by the soda manufacturers. 

When the sulphuret of sodium is mixed with chalk in certain propor- 
tions, and heated in a furnace, it is deprived of its sulphur, and is con- 
verted into carbonate of soda, the common soda of the shops. 

This \rell known salt, now sold in the state of crystals, [containing 62 

• Not in crystals, the form in which it is commonly sold as a horse medicine. These 
crystals contain upwards of half their weight (55 per cent.) of water. 



192 SODA Oft CAUSTIC SODA. 

per cent, of water,] at from 10s. to 12s. a ewt., has not as yet been ex- 
tensively tried as a means of promoting vegetation. The lowness of its 
price, however, and the fact that it is an article of extensive home man- 
ufacture, conjoined with the encouragement we derive from theoretical 
considerations — all unite in suggesting the propriety of a series of ex- 
periments with the view of determining its real value to the practical 
agricuhurist. The mode in which theory indicates that this compound 
is likely to act in promoting vegetation — as well as the crops to which it 
may be expected to be especially useful, will come under our considera- 
tion hereafter. 

Besides the common carbonate of soda above described, and which in 
the neighbourhood of Newcastle is manufactured from common salt to 
the amount of 30 or 40 thousand tons every year, there occur in nature 
two other compounds of soda with carbonic acid, in which the latter 
substance is present in larger quantity than in the soda of the shops. 
The sesqui-eavhonate, containing one half more carbonic acid, occurs in 
the soil in many warm climates (Egypt, India, South America, &c.), 
and at Fezzan, in Africa, is met with as a mineral deposit of such 
thickness as in that dry climate to allow of its being employed as a 
building stone. 

The 6z-carbonate is contained in the waters of many lakes, in Hunga- 
ry, in Asia, &c., and in many springs in all parts of the world. There 
can be no doubt that the waters of such springs are fitted to promote the 
fertility, especially of pasture land, to which they may be applied either 
by artificial irrigation, or by spontaneous overflow from natural outlets. 
Some of the Harrowgate waters contain a sensible quantity of this bi- 
carbonate, and over a large portion of the Yorkshire coal-field, a bed of 
rock is found, at various depths, the springs from which hold in solution 
a considerable portion of this salt. The Holbeck water of Leeds, ac- 
cording to Mr. West, owes its softness to the presence of this carbonate, 
and the water from the coal-mines in the neighbourhood of Wakefield 
is occasionally so charged with it, as to form troublesome saline incrus- 
tations on the bottoms of the steam boilers. Where these waters occur 
in sufficient abundance, they should not be permitted to escape into the 
rivers, until tliey have previously been employed in irrigating the land. 

It has occasionally been observed that natural springs in some locali- 
ties impart a degree of luxuriance to natural pasture, which is not to be 
accounted for by the mere effect of a constant supply of water. In 
such cases, the springs may be expected to contain some alkaline, or 
other mineral ingredient, which the soil is unable to supply to the plants 
which grow upon it, either in suflficient abundance, or with sufficient 
rapidity. 

5°. Soda or Caustic Soda. — When a solution of the corarnon soda of 
the shops is boiled v^dth quick-lime, it is deprived of its carbonic acid, 
and like the carbonate of potash (p. 187) is brought into the caustic state. 
In this slate it destroys animal and vegetable substances, and, unless 
very dilute, is injurious to animal and vegetable life. 

When common salt (chloride of sodium) is mixed with quick-hme in 
compost heaps, it is deprived by the lime of a portion of its chlorine, 
and is partially converted into this caustic soda. The action of the soda 
in this state is similar to that of caustic potash. Not only does it readi- 



SODIUM, PHOSPHATJIS OF SODA, AND CARBONATE OF lilME. 193 

ly supply soda to the Rowing plant, to which soda is necessary, but it 
also acts upon certain other substances which the plants require, so as 
to render them soluble, and to facilitate their entrance into the roots of 
plants. To the presence of soda in this caustic state, the efficacy of 
such composts of common salt and lime in promoting vegetation, is in 
part to be ascribed. 

6^. Sodiwn is a soft metal of a silver white colour, and, like potassi- 
um, light enough to float upon water. It is obtained by heating caustic 
soda wiih a mixture of charcoal and iron filings. It takes fire upon 
water — though not so readily as potassium — and combines with its oxy- 
gen to form soda. In the metallic state it is not known to occur in na- 
ture, and, therefore, does not directly act upon vegetation. With oxy- 
gen it forms 8oda,^~wijh chlorine, chloride of sodium (common salt), — 
and with sulpliur, sulphuret of sodium, — all of which, as already stated, 
ar€ more or less beneficial to vegetation. 

7°. Phosphates of Soda.-^W henlhe common soda of the shops is added 
to a solution of phosphoric acid in water, till elfervescence ceases, and 
the solution is evaporated to dryness, ])hosphate of soda is formed, and 
by the subsequent addition of as much more phosphoric acid — 6i-pbos- 
phate. These salts occur more or less abundantly in the ash of nearly 
all plants ; they are occasionally also detected in the soil, and one or 
other of them is almost always present in urine and other animal ma- 
nures. As we know from theory that these compounds must be grate- 
ful to plants, we are justified in ascribing a portion of the efficacy of animal 
manures, in promoting the growth of vegetables, to the presence of these 
phosphates, as well as to that of the phosphates of potash (p. 190). 
They are not known to occur in the mineral kingdom in any large quan- 
tity, neither are they articles of manufacture, hence their direct action 
upon vegetation has not hitherto been made the subject of separate ex- 
periment. 

VH.-^CALCIUM, LIME, CARBONATE OF LIME, SULPHATE OF LIME, NI- 
TRATE OF LIME, PHOSPHATES OF LIME, CHLORIDE OF CALCIUM, SUL- 
PHURET OF CALCIUM. 

.1°. Carbonate of Lime. — Chalk, marble, aud nearly all the lime- 
stones in common use, are varieties, more or less pure, of that com- 
pound of lime with carbonic acid vvhich is known to chemists as car- 
bonate of lime. It occurs of various colours and of various degrees of 
hardness, but in weight the compact varieties are very much alike, be- 
ing generally a little more than 2^ times (2-7) heavier than water. 
They all dissolve with effervescence in dilute muriatic acid (spirit of 
salt), and by the bubi)les of gas which are seen to escape when a drop 
of this acid is applied to them, limestones may in general be readily dis- 
tinguished from other varieties of rock. They dissolve slowly also in 
water which holds carbonic acid in solution ; and hence the springs 
which issue from the neighbourhood of deposits of limestone are gene- 
rally charged in a high degree with this mineral substance. 

The value of this carbonate of lime in rendering a soil capable of pro- 
ducing and sustaining a luxuriant vegetation depends, in part, it is true, 
on the necessity of a certain proportion of lime to the growth and full 
developement of the several parts of nearly all plants, but it performs also 



194 QUICK-LIME, CALCIUM, AND CHLORIDE OF CALCIUM. 

Other important offices, which we shall hereafter have occasion more 
fully to consider. 

2°. Lime or Quick-lime. — When limestone is burned along with coal 
or wood in kilns so constructed that a current of air can pass freely through 
them, the carbonic acid is driven off, and the lime alone remains. In 
this state it is generally known by the name of burned or quick-Wme^ 
from its caustic qualities, and is found to have lost nearly 44 per cent, of 
its original weight. 

The most remarkable property of quick-lime is its strong tendency to 
combine with water. This is displayed by the eagerness with which this 
liquid is drunk in by the lime in the act of slaking, and by the great heat 
which is at the same time developed. Slaked lime is a compound of 
lime with water, and by chemists is called a hydrate of lime. It con- 
tains 24 percent, of its weight of water. 

The action of quick-lime upon the land is one of the most important 
which presents itself to the observation of the practical agriculturist. 
Among other effects produced by it is that of hastening the decomposi- 
tion of vegetable matter either in the soil or in compost heaps ; but this 
effect is materially promoted by — if it be not wholly dependent upon 
— the presence of air and moisture. By this decomposition carbonic 
acid and other compound substances are produced, which the roots are 
capable of absorbing and converting into the food of plants. 

In this caustic state lime does not occur in nature, nor when exposed 
to the air does it long remain in this state. It gradually absorbs carbonic 
acid from the atmosphere, and is again converted into carbonate. This 
change takes place more or less rapidly in all cases where quick-lime is 
applied to the land, but the benefits arising from burning the lime do not 
disappear when it is thus reconverted into carbonate. On the contrary, 
the state of very fine powder, into which quick-lime falls on slaking, 
enables the carbonate of lime, subsequently formed, to be intermixed 
with the soil in a much more minute state of division than could be ob- 
tained by any mechanical means. This we shall hereafter see to be a 
most important fact, when we come to study in more detail the theory 
of the action of lime in the several states of combination, and under the 
varied conditions in which it is employed for the purpose of improving 
the land. 

3°. Calcium is a silver-white metal, which, by its union with oxygen, 
forms lime. It is not known to exist in nature in an uncombined state, 
is prepared artificially only with great difficulty, and therefore exercises 
no direct action on vegetable growth. 

4°. Chloride of Calcium. — When chalk or quick-lime is dissolved in 
muriatic acid, a solution of chloride of calcium is obtained. This solu- 
tion occurs in sea- water, in the refuse (mother-liquor) of the salt-pans, 
and is allowed to flow away in large quantities as a waste from certain 
chemical works. I have elsewhere stated the effects it has been ob- 
served to produce upon vegetable growth, [see Appendix,] and have re- 
commended the propriety of making experiments with the view of ren- 
dering useful some of those materials which in our manufactories are 
now suffered largely to run to waste. 

5°. Sulphuret of Calcium is a compound of sulphur and calcium, 
which may be formed by heating together chalk and sulphur in a covered 



SULPHATE AND NITRATE OF LIME. 195 

crucible. It is sometimes produced in nature, where moist decaying 
vegetable and animal matters are allowed to ferment in the presence of 
gypsum ; it may sometimes also be detected in the soil, and in the waters 
of mineral springs, and is contained largely in the recent refuse heaps 
of the alkali works. Like the sulphurets of potassium and sodium, al- 
ready described, it is fitted, when judiciously applied, to promote the 
growth especially of those plants in which sulphur has been recognized 
as a necessary constituent. 

6°. Sulphate of Lime, or gypsum, is a well known white crystalline 
or earthy compound, which occurs as an abundant mineral deposit in 
numerous parts of the globe. It is present in many soils, is contained 
in the waters which percolate through such soils, and in those of springs 
wliicli ascend from rocky beds in which gypsum exists, and is detect- 
ed in sensible proportions in the ashes of many cultivated plants. It 
is extensively employed in the arts, and in some countries not less ex- 
tensively as a means of promoting the fertility of the land. — [See Appen- 
dix, p. 1.] 

The gypsum of commerce contains nearly 21 per cent, of its weight 
of water, whicli it loses entirely on being exposed to a red heat. In 
some countries, a variety which is almost entirely free from water oc- 
curs in rocky masses, and is distinguished by the name o^ Anhydrite. 

Gypsum, when burned, has the property of being reduced with great 
ease into the state of an impalpable powder. This powder, however, 
combines so readily with the 21 per cent, of water it had previously lost, 
that if it be mixed with water to the consistence of a paste so thin that it can 
be poured into a mould, it sets and hardens in a few minutes into a solid 
mass. In this way burned gypsum is employed in making plaster casts 
and cornices. 

Burned gypsum consists of lime and sulphuric acid only — in the pro- 
portions of 41i of the former, to 58i of the latter. Its use as a manure, 
therefore, will be specially to promote the growth of those plants by 
which these two substances are more abundantly required, and upon 
soils in which they are already present in comparatively small propor- 
tion. 

7*^. JSitrale of Lime. — The production of nitrate of lime in artificial 
nitre-beds, on old walls, and on the sides of caves and cellars, especially 
in damp situations, has already been alluded to in Lecture VIII., [p. 
161.] It may be formed artificially by dissolving common limestone in 
nitric acid, and evaporating the solution. It constitutes a \^hite mass, 
which rapidly attracts water from the air, and runs to a liquid. It is 
produced naturally, and exists, as 1 believe, in soils containing lime, 
more commonly than has hitlierto been suspected. Its extreme solubili- 
ty in water, however, renders it liable to be carried downwards into the 
lower portions of the soil by every shower of rain— or to be actually 
washed away, when long continued wet weather prevails. 

When heated to dull redness with vegetable matter, the nitrate of 
lime is decomposed, and is converted into carbonate, or when exposed 
alone to a bright red heat, the nitric acid is expelled, and quick-lime 
alone remains. Hence where it really exists in plants, it cannot be de- 
tected in the ash, — and when present in soils, it must be separated by 



196 PHOSPHATE OF LIM«. 

"washing ihetn in water, before they are exposed to a heat sufficient to 
burn away the organic matter they contain. 

The details already entered into in the preceding lecture (pp. 169 to 
163) regarding ihe general action of nitric acid, in promoting the natural 
vegetation of the globe, render it unnecessary forme to dwell here on the 
special action of its compound with lime — more particularly as the entire 
subject of the action of lime upon the land will hereafter demand from 
us a separate consideration. 

The nitrate of lime cannot, as yet, be formed by art, at a sufficiently 
cheap rate to allow of its being manufactured for the use of the agricul- 
turist. 

PhospJiatf.s of Lime. — Lime combines with phosphoric acid in sev- 
eral proporiions, forming as many different compounds. Of these by 
far the most important and abundant in nature, certainly the most use- 
ful to the agriculturist, is the earth of bones. It will be necessary, how- 
ever, to advert shortly to two others, with the existence of which it is 
important for us to be acquainted. 

A. Earth of Bones is the name given to the white earthy skeleton that 
remains when the bones of animals are burned in an open fire until 
every thing combustible has disappeared. This earthy matter consists 
chiefly of a peculiar phosphate of lime, composed of 51i per cent, of 
lime, and 48i of phosphoric acid. This compound exists ready formed 
in the bones of all animals, and is the substance selected in the economy 
of nature to impart to them their strength and solidity. It is found in 
smaller quantity in those of young animals, while they are soft, and 
cartilaginous, — and the softening of the bones, which in after-life occurs 
as the result of disease, is caused by the unnatural abstraction of a greater 
portion of this earthy matter than is replaced by the food. 

This earthy phospliate constitutes about .57 per cent, of the dried bones 
of the ox, is present in lesser quantity in the horns, hoofs and nails, and 
is never absent even from the flesh and blood of healthy animals. It 
exists in the seed of many plants, in all the varieties of grain wliich are 
extensively cultivated for food, and in the ashes of most common plants. 
The ashes of leguminous, cruciferous, and composite plants, are es- 
j)ecially rich in this compound. 

If we consider that when animals die, their bones are chiefly buried in 
the earth, and that over the entire globe, animal life, in one or other of 
its forms, prevails, we shall not be surprised that, in almost every soil, 
the earth of bones should be found to exist in greater or less abundance. 
Nor can we have any difficulty in conceiving, if such be the case, 
whence plants draw their constant and necessary supplies of this 
substance. 

At the same time, it is true of this compound, as of all the others we 
have yet spoken of, as occurring in, and as necessary to the growth of, 
vegetables, — that some soils contain it in greater abundance than others, 
and that from some soils, therefore, certain plants will not readily obtain 
as much of this substance as they require. This is the natural principle 
on which the use of bone-dust as a manure chiefly depends. 

Hence of two marls both containing carbonate of lime, that will be 
most useful to the land which contains also, as many do, a notable por- 
tion of phosohate of lime ; and of two limestones, that will be preferred 



BOILED BONES AS A MANURE. 197 

in an agricultural district in which animal remains most abound. I 
shall have occasion to illustrate this point more fully, when in a subse- 
quent lecture I come to explain the natural origin of soils, and to trace 
their chemical constituents to the several rocky masses from which they 
appear to have been derived. 

Before dismissing this topic, however, there are one or two proper- 
ties of this bone earth which are of practical importance, and to which, 
therefore, I must shortly request your attention. It is insoluble in water 
or in solutions of soda or potash, but it dissolves readily in acids, such as 
the nitric or muriatic, and also, though less easily and abundantly, in 
common vinegar. It exists in milk, and is supposed to be held in solu- 
tion by a peculiar acid found in this liquid, and which is distinguished by 
the name oi^ lactic acid (acid of milk). 

It is slightly soluble also in a solution of carbonic acid, and of certain 
other organic acids which exist in the soil, and it is by means of these 
acids that it is supposed to be rendered capable of entering into the roots 
of plants. Wherever vegetable matter exists, and is undergoing decay 
in the soil, the water makes its way to the roots more or less laden with 
carbonic acid, and thus is enabled to bear along with it not only common 
carbonate of lime, as has been shown in a previous lecture (p. 47), but 
also such a portion of phosphate as may aid in supplying this necessary 
food to the growing plant.* 

In the bones of animals the phosphate is associated with animal gela- 
tine, which can be partially extracted by boiling bones in water under 
a high pressure. It has been observed, however, that the phosphate, 
when in a minute state of division, is slightly soluble in a solution of 
gelatine, and hence bones, from which the jelly has been partially ex- 
tracted by boiling, will be deprived of a certain proportion of their earthy 
matter also. They will have lost their gelatine, however, in a greater 
proportion, and hence, if again thoroughly dried, they will contain a 
larger per-centage of bone earth than when in their natural slate. In 
this country, bones are seldom boiled, I believe, either for the jelly they 
give, or as in France and Germany for the manufacture of glue, though 
in certain localities they are so treated in open vessels for the sake of the 
oil they are capable of yielding. Such boiled bones are said to act more 
quickly when applied to the land, but to be less permanent in their ef- 
fects. This may be chiefly owing to their not being so perfectly dry as 
the unboiled bones. Being thus moist, they will contain, in the same 
weight, a comparatively smaller quantity boih of the animal gelatine 

* If to a solution of bone earth in muriatic acid (spirit of salt), liquid ammonia (hartshorn) 
be added, the solution will become milky, and a white powder will fall, which is the earth 
of bones in an extremely minute state of division. If this powder be washed by repeated affu- 
sions of pure water, and be afterwards well shaken with water which is saturated with car- 
bonic acid, or through which a cunrent of this gas is made to pass, a sensible portion of the 
phosphate will be found to be taken up by the water. This will appear on decanting the 
solution and evaporating it to dryness, wlien a quantity of the white powder will remain be- 
hind. The mean of 10 experiments made in this way gave me 30 grains for the quantity of 
phosphate taken up by an imperial gallon of water. Wiiat takes place in this way in our 
hands, happens also in the soil. Not only does that which enters the root bear with it a por- 
tion of this compound where it exists in the soil, but tlie superabundant water also which 
runs off the surface or sinks through to the drains, carries with it to the rivers in its coursp 
a still larger quantity of this soluble compound, and thus gradually lessens that supply oT 
phosphate which either exists naturally in the soil, or has been ad.ied as a manure by the 
practical agriculturist. 



198 ACID OR BI-FHOSPHATE OF LIME. 

and of the earthy phosphate, while they will also be more susceptible of 
speedy decomposition when buried in the soil.* 

In solutions of common salt and of sal-ammoniac, the earth of bones 
is also slightly soluble, and cases may occur where the presence of 
these compounds in the soil may facilitate the conveyance of the earthy 
phosphate into the roots of plants. 

B. Acid or Bi- Phosphate of Lime. — When burned bones are reduced 
to powder, and digested in sulphuric acid (oil of vitriol), diluted with 
once or twice its weight of water, the acid combines with a portion of the 
lime, and forms sulphate of lime (gypsum), while the remainder of the 
lime and the whole of the phosphoric acid are dissolved. The solution, 
therefore, contains an acid phosphate of lime, or one in which the phos- 
phoric acid exists,- in much larger quantity than in the earth of bones. 
The true bi-phosphate, when free from water, consists of 7 li of phos- 
phoric acid, and 28i of lime. It exists in the urine of most animals, and 
is therefore an important constituent of liquid manures of animal origin. 

If the mixture of gypsum and acid phosphate, above described, be 
largely diluted with water, it will form a most valuable liquid manure, 
especially for grass land, and for crops of rising corn. In this liquid 
state, the phosphoric acid will diffuse itself easily and perfectly through- 
out the soil, and there will speedily lose its acid character by combining 
with one or other of the hasic\ substances, almost always^ present in 
every variety of land. 

Or if to the solution, before it is applied to the land, a quantity of pearl- 
ash be added until it begin to turn milky, a mixture of the phosphates 
with the sulphates of lime and of potash will be obtained, or — if soda be 
added instead of potash — of the phosphates with the sulphates of lime 
and of soda ; either of which mixtures will be still more efficacious 
upon the land, than the solution of the acid phosphates alone. 

Or to the solution of bones in the acid, the potash or soda may be added 
without further dilution, and the whole then dried up by the addition of 
charcoal powder, or even of vegetable mould, till it is in a sufficiently 
dry state to be scattered with the hand as a top-dressing, or buried iu 
the land by means of a drill. 

I have above alluded to the employment of bones in France and Ger- 
many, for the manufacture of glue. For this purpose the broken bones 
are digested in weak muriatic acid, by which the earthy matter is dis- 
solved, and the gelatine left behind. The gelatinous skeleton is boiled 
down for glue, and the solution of the bone earth is thrown away. This 
solution contains a mixture of the acid phosphate of lime with chloride 
of calcium, — and might be used up in any of the ways above described, 
with manifest benefit to the land. The glue prepared by this method, 
however, is said to be inferior in quality, and as the process is not adopt- 
ed in this country', the opportunity of making an economical application 
of this waste material is not likely to be often presented to the English 
farmer. 

' The relative value of crushed bones in these two states, is indicated by the price of the 
unboiled being about 7 guineas, while that of boiled is only about 4 guineas a ton. 

t Tliis word has already been used and explained— it is applied to potash, soda, ammonia, 
lime, magnesia, and other substances; which have the property of combining with acids (sul- 
phuric, nitric, &c.) and of thus neutralizing them, or depriving them of their acid qualities 
and effects, o . r e. 



NATIVE PHOSPHATE OF LIME. 199 

C. Native Phosphate of Lime or Apatite. — In some parts of the world, 
a hard mineral substance, commonly known by the name of Apatite, 
occurs in considerable quantity. It consists chiefly of a phosphate of 
lime, which differs but slightly in its constitution from the earth of bones, 
— containing 54^ per cent, of lime, while the latter contains only b\^ per 
cent. The composition of this mineral would lead us to expect it to 
possess a favourable action upon vegetation, and this anticipation has 
been confirmed by some experiments made with it on a limited scale by 
Sprengel. — [Cheinie, I., p. 64.] 

It occurs occasionally in mineral veins, especially such as are found 
in the granitic and slate rocks. Masses of it are met with in Cumber- 
land, in Cornwall, in Finland, in the iron mines of Arendahl in Nor- 
way, and in many other localities. A variety of it distinguished by the 
name of phosphorite is said to form beds at Schlachenwalde in Bohemia, 
and in the province of Estremadura in Spain. From the last of these 
localities being the most accessible, the time may come when the high 
price of bones may induce our enterprising merchants to import it, for 
the purpose of being employed in a finely powdered state as a fertilizer 
of the land. 



M of Grape 3 of 

Sugar. Water 



I 



LECTURE X. 

Inorganic constituents of plants continued.—Magnesia, Alumina, Silica, and the Oxides of 
Iron and Manganese.— Tabular view of the constitution of the inorganic substances de- 
scribed.— Proportions in which these several substances are found in the plants cultivated 
for food.— Extent to which these plants exhaust the soil of inorganic vegetable food.— State 
m which the inorganic elements exist in plants. 

§ 1. Inorganic constituents of plants continued, 

VIII. MAGNESIUM, MAGNESIA, CARBONATE, SULPHATE, NITRATE, AND 

PHOSPHATE OF MAGNESIA, CHLORIDE OF MAGNESIUM. 

1°. Carbonate of Magnesia is a tasteless earthy compound, which in 
some parts ofthe world forms rocky masses and veins of considerable 
height and thickness. It occurs more largely, however, in connection 
with carbonate of lime in the magnesian limestones, so well known in 
the eastern and northern parts of England, — and in similar rocks, dis- 
tinguished by the name of doloinites or of dolomitic limestones, in va- 
rious countries of Europe. The pure, exceedingly light, white magne- 
sia of the shops, is partly extracted from the magnesian limestone, and 
partly from the mother liquor of the salt pans, which generally contains 
much magnesia. 

_ When pure and dry, carbonate of magnesia consists of 43i of magne- 
sia, and 51f of carbonic acid. It dissolves readily in diluted acids (sul- 
phuric, muriatic, and acetic,) the carbonic acid at the same time esca- 
ping with effervescence. 

Existing as it does in many solid rocks, this carbonate of magnesia 
may be expected to be present in the soil, and it is found in the ashes of 
many plants. Of the ashes of some parts of plants it constitutes one- 
sixth ofthe entire weight. 

When exposed to the air in a finely divided state, it gradually absorbs 
a quantity of moisture from the atmosphere, equal to two-thirds of its 
own weight. In this state, it dissolves in 48 times its weight of water, 
though, wheii dry, it is nearly insoluble. Like carbonate of lime it is 
also soluble in water impregnated with carbonic acid, but in a some- 
what greater degree. In this state of solution it may be readily carried 
into the roots, and be the means of supplying to the parts of living ve- 
getables a portion of that magnesia which is necessary to their perfect 
growth. 

Soils containing much of this carbonate of magnesia are said to be 
highly absorbent of moisture, and to this cause is ascribed the coldness of 
such soils.— [Sprengel, Chemie, I., p. 646.] This opinion is, however, 
open to doubt, 

2°. Magnesia or Caustic Magnesia, the calcined magnesia of the 
shops.--^hen the carbonate of magnesia is heated to redness in the 
open air, it parts with its carbonic acid much more readily than lime 
does, and is brought into the state of pure or caustic magnesia. In this 
state it does not occur in nature, but it is occasionally met with in com- 



CAUSTIC OR CALCINED MAGNESIA. 201 

bination with about SO per cent, of water. When magnesian lime- 
stones or dolomites are burned, the quick-lime obtained often contains 
caustic magnesia also in considerable quantity. This mixture is fre- 
quently applied to the land, and, as is well known in many parts of 
England, with injurious effects, if laid on in too large quantities. The 
cause of this hot or burning nature, as it is called, of magnesian lime, is 
not very satisfactorily ascertained. I shall, however, state two or three 
facts, which may assist in conducting us to the true cause. 

1°. Quick-lime dissolves in 750 times its weight of water, at the or- 
dinary temperature of the atmosphere, while pure magnesia requires 
5142 times its weight. The magnesia, therefore, is not likely to injure 
living plants directly by entering into their roots in its caustic state, since 
lime which is seven times more soluble produces no injurious effect. 

2°. It seems to be the result of experience, that magnesia in the state 
of carbonate is but slightly injurious to the land ; some deny that in this 
state it has any injurious effect at all. This I fear is doubtful ; we may 
infer, however, with some degree of probability, that it is from some 
property possessed by magnesia in the caustic state, and not possessed, 
or at least in an equal degree, either by quick-lime or by carbonate of 
magnesia, that its evil influence is chiefly to be ascribed. 

3°. When exposed to the air, quick-lime speedily absorbs water and 
carbonic acid from the air, forming first a hydrate'^ in fine powder, and 
then a carbonate. Caustic magnesia absorbs both of these more slowly 
than lime does, and in the presence of the latter, or when mixed with it, 
must absorb them more slowly still, since the lime will seize on the 
greater portion of the moisture and carbonic acid which exists in the air, 
immediately surrounding both. When slaked in the air also, the lime 
may be transformed in great part into carbonate, while the magnesia 
still remains in the state of hydrate, and it is a property of this hydrate 
to attract carbonic acid more feebly and slowly, even than the newly 
burned magnesia as it comes from the kiln. Hence when buried in the 
soil, after the lime has become nearly all transformed into carbonate, the 
magnesia may still be all either in the dry caustic state, or in that of a 
hydrate only. 

4°. Now there exist in (he soil, and probably are exuded from the 
living roots, various acid substances, both of organic and of inorganic 
origin, which it is one of the functions of lime, when applied to the land, 
to combine with and render innoxious. But these acid compounds unite 
rather with the caustic magnesia, than with the lime which is already 
in combination with carbonic acid — and form salts, j which generally are 
much more soluble in water than the compounds of lime with the same 
acids. Hence the water that goes to the roots reaches them more or 
less loaded with magnesian salts, and carries into the vegetable circula- 
tion more magnesia than is consistent with the healthy growth of the 
plant. 

It is hazardous to reason from the phenomena of animal to those of 

* Compounds of substances with water are called hydrates (from the Greek word for wa- 
ter.) Thus slaked lime, a compound of lime with water, is called hydrate of lime — and the 
native compound of magnesia with water, alluded to in the text, is called hydrate of mag- 
nesia. 

t Compounds of the fioses, — potash, soda, lime, magnesia, &c., — with octds, — sulphuric, 
muriatic, nitric, acetic (or vinegar), «fec., — are called salts. 



202 MAGNESIUM, AND CirL0RrDE OF MAGKESIUM. 

vegetable physiology, yet if lime and magnesia have the power of dif- 
ferently affecting the animal economy, why may they not also very 
differently affect the vegetable economy ? And since in the same cir- 
cumstances, and in combination with the substances they meet with 
in the same soils, magnesia is capable of entering more largely into 
a plant by its roots— may not magnesia be considered capable of poi- 
soning a plant, when lime in the same condition would only improve 
the soil ? *^ ^ 

I have said that it may be doubted whether magnesia in the state of 
carbonate is wholly unhuriful to the land. This doubt rests on the fact 
that the magnesia retains its carbonic acid more feebly than lime does 
—and therefore its carbonate is the more easily decomposed when an 
acid body comes in contact with both. Though, therefore, the mag- 
nesian carbonate will not lay hold of all acid matter so readily and sureFy 
as caustic magnesia may, still occasions may occur where acid matters 
being abundant in the soil, so much carbonate of magnesia may be de- 
composed and dissolved as to render the water absorbed by its roots 
destructive to the health or life of a plant. 

In reference to this point, however, it must be distinctly understood, 
that magnesia is one of the kinds of inorganic food most necessary to 
plants, that a certain quantify of it in the soil is absolutely necessary to 
the growth of nearly all cultivated plants, and that it is only when it is 
conveyed to the roots in too large a (juantity, that it proves iniurioiis to 
vegetable life. 

5°. Magnesium is the metallic basis of magnesia. Little is known 
of Its properties, owing to the difficulty of preparing it in any consider- 
able quantity for the purpose of experiment. It is a white metal, which, 
when heated in the air, takes fire and burns, combining with the oxygen 
of the atmosphere, and forming magnesia. It is not known to occur in 
nature in an elementary form, and therefore is not supposed directly to 
influence vegetation. 

6°. Chloride of Magnesium.— -When calcined or carbonated magne- 
sia IS dissolved in muriatic acid, and the solution evaporated to dryness, 
a white mass is obtained which is a chloride of magnesium, consisting of 
inagnesiijm and chlorine only. This compound occurs not unfrequently 
in the soil, associated with chloride of calcium. It is met with also in 
the ash of plants, while in sea water, and in that of some salt lakes, it 
exists in very considerable quantity. Thus 100 parts of the water of 
the Atlantic have been found to contain 3i of chloride of magnesium, 
while that of the Dead Sea yields about 24 parts of this compound.* 
Hence it is present in great abundance in the mother liquor of the salt 
pans, and it is from the refuse chloride in this liquor that the mac^nesia 
of the shops, as above stated, is frequently prepared. ^ 

The chloride of magnesium has not hitherto been made the subject of 
direct experiment as a fertilizer of the land. From the fact, however, 
that plants require much magnesia and some chlorine, there is reason to 
believe that, if cautiously applied, it might prove beneficial in some soils, 
and especially to grain crops. Its extreme solubility in water, however, 
suggests the use of caution in its application. The safest method is to 

and nTaff/s of c?mmo!f sau' '^' ""'^^ ^'' ''°"''^''' "^^ «'°"' '^ ^^ '''''''^' <>^ ««'«•»'". 



NITRATE, SULPHATE, AND PHOSPHATE OF MAGNESIA. 203 

dissolve it in a large quantity of water, and to apply it to the young 
plant by means of a water-cart. In this way the refuse of the salt 
works might, in some localities, be made available to useful purposes. 

The chloride of magnesium is decomposed both by quick-lime and by 
carbonate of lime; hence when applied to a soil "containing lime in 
either of tliese states, chloride of calcium and caustic or carbonated mag- 
nesia will be produced. 

^ 7°. Nitrate of Magnesia is formed by dissolving carbonate of magne- 
sia in hitric acid, and evaporating the solution. It attracts moisture from 
tlie air with great rapidity, and runs info a liquid. It is probably formed 
naturally in soils containing magnesia, in the sam.e way as nitrate of 
lime is known to be produced in soils containing lime. [See Lecture 
A^III., p. 159.] No direct experiments have yet been made as to i(s 
effects upon vegetation ; but there can be no doubt that it would prove 
highly beneficial, could it be procured at a sufficiently cheap rate to ad- 
mit of its economical application to the land. 

8^. Sulphate of Magnesia— {he common Epsom salts of the shops 

IS formed by dissolving carbonate of magnesia in diluted sulphuric acid. 
It exists in nearly all soils Avhich are formed from, or are situated in, 
ihe neighbourhood of rocks containing magnesia. In some soils it is so 
abundant that in dry -weather it forms a white efflorescence on the sur- 
face. This has been observed to take place in Bohemia, Hungary, and 
parts of Germany, and it may be frequently seen in warm summer 
weather in the neighbourhood of Durham.* 

This salt has been found by Sprengel to act upon vegetation precisely 
in the same way as gypsum does, and on the same kind of plants. It 
must be used, however, in smaller quantity, owing to its great solubili- 
ty. Its higher price will prevent its ever being substituted for gypsum, 
as a top-dressing for clover, &c., but k is worth the trial, whetJier corn 
plants, the grain of which contains much magnesia, might not be bene- 
fitted by the application of a small quantity of this sulphate—along with 
such other substances as are capable of yielding the remaining constit- 
uents which compose the inorganic matter of the grain. Its price is not 
too high to admit of this more restricted application.! 

9°. Phosphate of Magnesia. — Magnesia exists in combination with 
phosphoric acid, in the solids and fluids of all animals, though not so 
abundantly as the phosphates of lime. In most soils phosphate of mag- 
nesia is probable present in minute quantity, since in the ashes of some 
varieties of grain it is found in very considerable proportion. 

Its action upon vegetation has never been tried directly, but as it 
exists in urine, and in most animal manures, a portion of their efficacy 
may be due to its presence. In turf aslies, which often prove a valua- 
ble manure, it is sometimes met with in appreciable quantity, and their 
beneficial operation in such cases has been attributed in part to the agen- 
cy of this phosphate. 

• It occasionally collects beneath the plaster of old walls in Durham. In one of the lower 
rooms of the old Exchequer buildings, I found it forming an extensive layer nearly half an 
mch thick, beneath the damp plaster. The magnesia is derived from the magnesian lime- 
stone, used both for mortar and for building stone. 

t Its price in Newcastle in the state of crystals, is about 10s. a cwt. The impure salt col- 
ectedatthe alum works on the Yorkshire coast, might be obtained, I should suppose, for 
little more than half this price. 



204 ALUMINA THE PRINCIPAL CONSTITUENT OF CLAYS. 

IX. ALUMIxVIUM, ALUMINA, SULPHATE AND PHOSPHATE OF 

ALUMINA — ALUM. 

1°. Aluminium is another of those rare and little known metals, the 
existence of which was established by Sir H. Davy. In combination 
with oxygen it forms alumina^ and in this state it exists in such abun- 
dance in nature, as to form a large portion of the entire crust of the 
globe. 

2°. Alumina, the earth of Alum. — When common alum is dissolved 
in water, and a solution of carbonate of soda or of ammonia is added to 
it, a bulky white powder falls, which, when collected on a filter, well 
washed and dried, is nearly pure alumina. This substance occurs on 
the surface of the earth in a pure state only in some rare minerals, such 
as the corundum, the sappliire, and the ruby, — but it constitutes a large 
proportion of all the slaty and shaley rocks. It is the principal ingre- 
dient also of all clays (pipe-clay for example) and clayey soils, which 
increase in tenacity in proportion to the quantity of alumina they contain. 

When pure, it is a white tasteless earthy substance, which adheres to 
the tongue, has a density of 2-00, and is insoluble in water, but dissolves 
readily in caustic potash and soda and in most acids, at least when new- 
ly thrown down from a solution of alum. When heated to redness, 
however, it becomes hard and dense, as in burned clay and fire bricks, 
and can then only be dissolved with extreme difficulty, even by the 
strongest acids. Though it exists so largely in the soil, it contributes 
but little in a direct manner to the nourishment of plants. The ash they 
leave contains in general but a very small per-centage of alumina, as 
will more clearly appear hereafter, — the principal agency, therefore, of 
this ingredient of the soil is most probably of an indirect, perhaps of a 
mechanical kind. 

It has been stated in a preceding Lecture (p. 23), that charcoal has 
the property of absorbing gaseous substances, such as ammonia, from 
the atniosphere, and that the action of charcoal powder, in promoting 
vegetation, has been in a great measure ascribed to this property: The 
same property, we have also seen (p. 136), is ascribed to gypsum, and 
hence its fertilizing action has been explained in a similar way. Alum- 
ina is said to be equally absorbent of ammonia ; and the use of burned 
clay as a top-dressing, so strongly recommended by General Beatson, 
\^New System of Cultivation, London, 1820,] is ascribed to its power 
of abstracting ammonia from the air, and fixing it in the soil ready to be 
conveyed by the rains to the roots of the plants that grow upon it [Liebig, 
p. 90.] It has been already shown (p. 136,) that this mode of ac- 
counting for the action of gypsum is not satisfactory as a sole cause — in 
the case of alumina, the fact of its absorbing ammonia is hypothetical,* 
and therefore the explanation founded upon this fact is not to be impli- 
citly relied upon. 

3°. Sulphate of Alumina. — When alumina is digested in diluted sul- 

Because clays of many varieties — pipeclay for example — contain traces of ammonia, 
which they evolve when moistened with a solution of caustic potash,— it is inferred that 
they have absorbed this ammonia from the atmosphere. The same inference is drawn 
from tlie fact of its presence in oxide of iron. — [Liebig's Organic Chemistry applied to Agri^ 
culture, p. 89.] — In neither case does the inference appear to me fo be necessary. Much of 
the ammonia may have been formed in the soil, during the oxidation of the iron itself, or 
during the decay of vegetable and animal substances. — See above, Lecture VIII., p. 153. 



SULPHATE AND PHOSPHATES OF ALUMINA, ALUM. 205 

phuric acid, it readily dissolves, and forms a solution of sulphate of 
alumina. This solution is characterized by a remarkable and almost 
peculiar sweetish astrin.^ent taste. When evaporated to dryness it yields 
a white salt, which dissolves in twice its weight of water only, and when 
exposed to the air, attracts moisture rapidly, and spontaneously runs to 
a liquid. This salt exists in some soils, especially in those of wet, 
marshy, and peaty lands. 

No experiments have yet been made with the view of determining its 
direct influence upon vegetation. 

4°. Phosphates of Alumina. — In combination with phosphoric acid, 
alumina forms one compound well known to mineralogists, by the name 
oi ivavellite. This mineral, however, occurs in too small quantity to be 
an object of interest to the agriculturist. 

Phosphoric acid is disseminated in some form or other throughout our 
clayey soils, though in very small and variable quantity. It is most 
probable that in these soils a portion of the acid at least is in combina- 
tion with the alumina in the state of phosphate. One of the most diffi- 
cult problems in analytical chemistry is to effect a perfect separation of a 
small proportion of phosphoric acid from alumina, and rigorously to esti- 
mate its quantity ; hence in the greater part of the analyses of soils hitherto 
published, this most important ingredient in a fertile soil (the phosphoric 
acid), when in combination with, or in presence of alumina, has either 
been altogether neglected, or rudely guessed at, or indicated by a rough 
approximation only. We have no direct proof, therefore, of the extent 
to which the phosphates of alumina exist in different soils. 

5°. Alum. — The common alum of the shops owes its well known 
sweetish astringent taste to the presence of the above sulphate of alumi- 
na. It consists in 100 parts of about 40 of sulphate of alumina, 14i of 
potash, [described p. 189,] and 45^ of water. Alum is formed naturally 
on many parts of the earth's surface, especially as an efflorescence on 
certain soils, and on some rocks when exposed to the air, — as on the 
alum shales of the Yorkshire coast. It is largely manufactured by cal- 
cining, and afterwards washing these alum shales. 

Alum has not been extensively tried as a manure. Its composition, 
however, would lead us to expect it to exert a beneficial influence on the 
growth of many plants — while the price, especially of the less pure va- 
rieties, is such as to admit of its being applied to the land at a compara- 
tively small cost. From some experiments made on a small scale, 
Sprengel considers it highly worthy the attention of the practical agri- 
culturist. 

X. — SILICA, SILICON, SILICATES OF POTASH, OF SODA, OF LIME, OF 
MAGNESIA, AND OF ALUMINA. 

1°. Silica. — The chief ingredient in all sand-stones and in nearly all 
sands and sandy soils, is known to chemists by the name of silica. Flints 
are nearly pure silex or silica— common quartz rock is another form oC 
the same substance — while the colourless and more or less transparent 
varieties of rock crystal and chalcedony present it in a state of almost 
perfect purity- It exists abundantly in almost all soils, constituting 
what is called their siliceous portion, and is found in the ashes of all 
plants without exception, but especially ix) those of the grasses. Silica. 
18 



206 SILICA, SILICON, SILICATES OF POTASH A>'D SODA. 

is without colour, taste, or smell, and cannot be melted by the strongest 
heat. As it occurs in the mineral kingdom — in the stale of flint, of 
quartz, or of sand — it is perfectly insoluble in pure water, either cold or 
hot, does not dissolve in acid and very slowly in alkaline solutions. 
When mixed with potash, soda, or lime, and heated in a crucible to a 
high temperature, it melts and forms a glass. Windoiv and plate glass 
consists chiefly of silica, lime, and soda, jiint glass contains Ihharge 
{oxide of lead] in place of the lime. But though the various forms of 
more or less pure silica, which are met with in the mineral kingdom, 
are absolutely insoluble in water, yet it sometimes occurs in nature, and 
can readily be prepared in a stale in which pure water, and even acid 
solutions, will take it up in considerable quantity. In this state it may 
be obtained by reducing crown-glass to a fine powder, and digesting it 
in strong muriatic acid, or by melting quartz sand in a large quantity of 
potash or soda, and afterwards treating the glass that is formed with di- 
luted muriatic acid. 

Silica is one of the most abundant substances in nature, and in com- 
bination with potash, soda, lime, magnesia, and alumina, it forms a 
large portion of all the so-called crystalHne (granitic, basaltic, &c.) 
rocks. The compounds of silica, with these bases, are called silicates. 
By the action of the air, and other causes, these silicates undergo decom- 
position, as glass does when digested with muriatic acid, and the silica 
is separated in the soluble state. Hence its presence in considerable 
quantity in the waters of many mineral and especially hot mineral 
springs, and in appreciable proportion in nearly all waters that rise from 
any considerable depth beneath the surface, or have made their way 
through any considerable extent of soil. 

In the substance of living vegetables it exists, for the most part, in 
this state of combination — as well as in the form of an extrt mely deli- 
cate tissue, of which the fibres are exceedingly minute, and therefore 
expose a large surface to the action of any decomposing agent, or of any 
liquid capable of dissolving it. In the compost heaps these silicates 
undergo decompositic n, — and the more readily the less they have been 
previously dried, or the greener they are, — and the silica of the plant is 
liberated in a soluble state. Whether or not, when thus liberated, it 
will be carried, vncornbined, into the roots of the plants by the water 
they absorb, will depend upon the quantity of potash or soda in the" 
compost or in the soil, and upon other circumstances hereafter to be 
explained. 

2°. Silicon is known only in the state of a dark brown powder, which 
has not as yet been met with in nature in an elemenlary form, and is 
prepared by the chemist with considerable difliculty. When heated in 
the air, or in oxygen gas, it burns, combines with oxygen, and is con- 
verted into silica. Silica, therefore, in its various forms, is a compound 
of silicon with oxygen. It consists of 48 per cent, of the former and 52 
per cent, of the latter. 

3°. Silicates of Potash and Soda. — When finely powdered ijuariz, 
flint, or sand, is mixed with from one-lialf to three times its weight of 
dry carbonate of potash or soda, and exposed to a strong heat in a cruci- 
ble, it readily unites with the potash or soda, and forms a glass. This 
gl^ss is a nlicate or a mixture of two or mnsre silicates of potash or soda. 



DECOMPOSED BY THE CARBONIC ACID OF THE AIR. 207 

Silica combines with these alkalies* in various proportions. If it be 
melted with much potash, the glass obtained will be readily soluble in 
water; if with little, the silicate which is formed will resist the action 
of water for any length of time. Window and plate-glass contain 
much silicate of potash or soda. A large quantity of alkali renders 
these varieties of glass more fusible and more easily worked, but at the 
same time makes them more susceptible of corrosion or tarnish by the 
action of the air. 

The insoluble silicates of potash and soda exist also in many mineral 
substances. In the felspar and mica, of which granite in a great mea- 
sure consists, they are present in considerable quantity. The former 
(felspar) contains one-third of its weight of an insoluble silicate of potash, 
consisting of nearly equal weights of potash and silica. In the variety 
called albite or cleavelandite, silicate of soda alone is found, wliile in 
some other varieties a mixture of both silicates is present. In mica from 
12 to 20 per cent, of the same silicate of potash occurs, but soda can 
rarely be detected in this mineral. The trap-rocks also (whin, basalt, 
green-stone), so abundant in many parts of oi]r island, consist almost 
entirely o? silicates. Among these, however, the silicates of potash and 
soda rarely exceed 5 or 6 per cent, of the whole weight of the rock, and 
are often entirely absent. 

These insoluble silicates also exist in the stems and leaves of nearly 
all plants. They are abundant in the stems of the grasses, especially 
in the straw of the cultivated grains, and form a large proportion of the 
ash which is left when these stems are burned [p. 178.] 

It is important to the agriculturist to understand the relation which 
the carbonic acid of the atmosphere bears to these alkaline silicates which 
occur in the mineral and vegetable kingdom. Insoluble as they are in 
water, they are slowly decomposed by the united action of the moisture 
and carbonic acid of the air, the latter taking the potash or soda from the 
silica, and forming carbonates of these bases. In consequence of this 
decomposition the rock disintegrates and crumbles down, while the so- 
luble carbonate is washed down by the rains or mists, and is borne to 
the lower grounds to enrich the alluvial and other soils, or is carried by 
the rivers to the sea. 

In some cases, as in the softer felspar of some of the Cornish granites, 
this decomposition is comparatively rapid, in others, as in the Dartmoor 
and many of the Scottish granites, it is exceedingly slow, — but in all 
cases the rock crumbles to powder long before the whole of the silicates 
are decomposed, so that pofash and soda are always present in greater 
or less quantity in granitic soils, and will continue to be separated from 
the decaying fragments of rock for an indefinite period of time. 

But the silica of the febpar, or mica, or zeoliticf trap, when thus de- 
prived of the potash with which it was corribined, is in that peculiar state, 
in which, as above described [p. 206], it is capable of being dissolved 
in small (]uantity by pure water, and more largely by a solution of 
carbonate of potash or soda. Hence the same rains or mists which dis- 

• Potash, soda, and ammonia are called alltalics ; lime and magnesia are alkaline earths. 
See Lecture III., p. 51, note, 

t The trap-rock3 always more or less abound in zeoUtic minerals, of which there is a great 
variety, and in which nearly all the alkali present in these (trap) rocks Is contained. 



208 SILICATES OF LIME IN THE TRAP-ROCKS. 

solve the alkaline carbonates so slowly formed, take up also a portion of 
the silica, and convey it in a state of solution to the soils or to the rivers. 
Thus, with the exception of the dews and rains which fall directly from 
the heavens, few of the supplies of water by which plants are refreshed 
and fed, ever reach their roots entirely free from silica, in a form in 
which it can readily enter into their roots, and be appropriated to their 
nourishment. 

In the farm-yard and the compost-heap, where vegetable matters are 
undergoing decomposition, the silicates they contain undergo similar de- 
compositions, and, by similar chemical changes their silica is rendered 
soluble, and thus fitted, when mixed with the soil, again to minister to 
the wants and to aid the growth of new races of living vegetables. 

4°. Silicates of Lime. — A mixture of sand or flint with quick-lime 
readily melts and forms a glassy silicate or a mixture of two or more 
silicates of lime. These sihcates are ako [nesent in large quantity in 
window and plate-glass, and in some of the crystalline* (granite and 
trap) rocks. In felspar and mica, which abound, as we have seen, in 
the alkaline silicates, it is rare that any lime can be detected. In that 
variety of granite, however, to which the name of syenite is given by 
mineralogists, hornblende takes the place o^ mica, and some varieties of 
this hornblende contain from 20 to 35 per cent, of silicate of lime. This 
silicate (containing 38 per cent, of lime) is almost always present in the 
basaltic and trap-rocks, and sometimes, as in the augiticf traps, in a 
proportion much larger than that in which it exists in the unmixed horn- 
blende. To this fact we shall have occasion to revert when we come 
to consider the relative fertility of difierent soils and the causes on which 
the ditference of their several productive powers most probably depends. 

Silicates of lime are also found in the ash, and probably J exist in the 
living stem and leaves of plants. 

Like the similar compounds of potash and soda, the silicates of lime 
are slowly decomposed by the united agency of the moisture and the 
carbonic acid of the atmosphere. Carbonate of lime is formed, and 
silica is set at liberty. This carbonate of lime dissolves in the rains or 
dews which descend loaded with carbonic acid, [see page 46,] and the 
same waters take up also a portion of the soluble silica and diffuse both 
substances uniformly through the soil in which the decomposition takes 
place, or bear them from the higher grounds to the rivers and plains. 
The sparing but constant and long-continued supply of lime thus af- 
forded to soils which rest upon decayed traj), or which are wholly made 
up of rotten rock, has a material influence upon their well-known agri- 
cultural capabilities. 

5°. Silicates of Magnesia. — In combination with magnesia in differ- 
ent proportions, silica forms nearly the entire mass of those common 
minerals known by the names of serpentine and talc. In hornblende 
also and augite, silicates of magnesia exist in considerable quantity. 

* So called because the minerals of which they consist are generally in a. crystallized slate. 

t Rocks of which the mineral called augite forms a more or less considerable part. 

1 1 say probably, because if nncombined silica be present in hay or straw along with car- 
bonate or oxalate of lime, the heat employed in completely burning away the organic matter 
m&y be sufficient to cause the lime and silica to unite and form a silicate which will after- 
wards be found in the ash, though none previously existed in the stem. 



I 



I 



Silicates or ALtJMi>' A. 209 

They mu^t, therefore, be present in greater or less quantity in soils 
which are directly formed from the decomposition of such rocks. Like 
the silicates of lime, however — though more slowly than these — they 
will undergo gradual decomposition by the action of the carbonic acid 
of the atmosphere, and of the acids produced in the soil by vegetation 
and by the decay of organic matter. The magnesia, like the lime, will 
thus be gradually brought down, in a state of solution (p. 200), from the 
higher grounds, or washed out of the soil, till at length it may wholly 
disappear from any given spot.* 

6°. Silicates of Alumina. — Silica combines with alumina also in vari- 
ous proportions, forming siliciates, which exist abundantly in nature in 
the crystalline rocks, and may also, like the other silicates, be formed 
by art. Felspar, mica, hornblende, and the augites, which abound in 
the trap-rocks, all contain much alumina in combination with silica, and 
we shall probably not be very far from the truth in assuming that up- 
wards of one-half by weight of the trap-rocks in general — as well as of 
the hornblendes, micas, and felspars, of which so large a part of the 
granitic rocks is composed— -consists of silicates of alumina. The alu- 
mina itself in these several minerals varies fVom 11 to 38 per cent., but 
generally averages about 20 per cent, of their entire weight. 

These silicates, when they occur alone, unmixed or uncombined with 
other silicates, decompose very slowly by the action of the atmosphere. 
They disintegrate, however, and fall to powder, when the alkaline sili- 
cates with which they are associated in felspar, &c., are decomposed and 
removed by atinospheric causes. In this way the deposits of porcelain 
clay, so common in Cornwall and in other countries, have been pro- 
duced from the disintegration of the felspathic rocks, and the clayey soils 
which occur in gianite districts have not unfrequently had a similar origin. 

When contained in the soil, the silicates of alumina undergo a slow 
decomposition from the action of the various acid substances to which they 
are exposed. A portion of their alumina is dissolved and separated by 
these acids, and in this soluble state is either conveyed to the roots of 
plants or is washed from the soil by the rains — or by the waters that 
arise from beneath. 

The ash of plants contains only a very small proportion of alumina, 
yet even this small quantity they cannot derive from the silicates of this 
substance, since these are all insoluble in water— as alumina itself is. 
They obtain it, therefore, from some of those soluble compounds of alu- 
mina of which I have spoken as being either occasionally present (pp. 
204-5), or as being naturally formed in the soil. 



General remarks on these Silicates. -~0{ all these silicates it may be 
remarked in general — 

1°. That besides existing in the minerals above-mentioned, and from 
which they are conveyed into the soil, they are also sloivly formed in the 

* I am indebted to Sir Charles Lemon for the analysis of a soil, on part of his own proper, 
ty, resting on serpentine, and bearing only Erica "vagans, Which illustrates the statement in 
the text. This soil consists of silica 70, alumina with a trace of gypfsum 20, oxide of iron 62, 
and veeetable matter 38 per cent. If this soil has been formed from the rock on which it 
rests, the magnesia has been wholly washed out. Its constitution, however, points rather to 
a decayed felspar or slate rock, as the source from which it has been derived. 






210 GENERAL REMARKS ON THESE SILICATES. 

sail itself, when the ingredients of which they severally consist are na- 
turally present in, or are artificially added to, the soil. Hence, the ad- 
dition of potash or soda to the land may cause the production of sili- 
cates of these alkalies — probably soluble silicates — which water will 
be capable of dissolving and bearing to the extremities of the roots. 
Hence also, in a sandy soil, the addition of lime may give rise to the 
production of insoluble silicates of this earth, — and the beneficial effect 
of the lime upon the land may thus sooner cease to be observable than 
in soils of a different character, where it is not so liable to be locked up 
in an insoluble state of combination ; and 

2°. That with the exception of those of potash and soda, which con- 
tain much alkali, these silicates are all insoluble in water, and thus not 
directly available to the nutrition of plants. Except those of alumina, 
however, they are all slowly decomposed by atmospheric agents, and 
their consthuent elements thus brought, to a certain extent, within the 
reach of plants ; while, without exception, they are all capable of de- 
composition in the soil by the agency of the acid substances, chiefly or- 
ganic, which there exist, or which are produced during the growth and 
decay of vegetable substances. From this latter source, the chief supply 
of the ingredients contained in the silicates, is, in most soils, derived by 
living plants. 

To this cause is attributed the surprising effect often observed to fol- 
low from the addition of vegetable matter to a sandy soil on which a 
previous addition of lime had ceased to produce any further beneficial 
effect. The organic acids formed by the vegetable matter during its de- 
cay decompose the silicates of lime previously produced, and thus liber- 
ate the lime from its insoluble state of combination. But when the sili- 
cates have been all decomposed by this agency, the further addition of ve- 
getable matter ceases necessarily to prod uce the same remarkable effects. 



XI.-^THE OXIDES, SULPHURETS, SULPHATES, AND CARBONATES OF IRON. 

1°. Oxides of Iron. — It is well known that when metallic iron is ex- 
posed to moist air, it gradually rusts and becomes covered with, or whol- 
ly changed into, a crumbling ochrey mass of a reddish brown colour. 
This powder is a compound of iron and oxygen only, containing 69^ per 
cent, of the former, and 30 j per cent, of the latter. 

When iron is heated in the smith's forge, and then beat on the anvil, a 
scale flies off which is of a black colour, and when crushed gives a black 
powder. This also consists of iron and oxygen only, but the proportion 
of oxygen is not so great as in the red powder above described. In both 
cases the iron has derived its oxygen from the atmosphere. 

To these compounds of iron, with oxygen, the name n{ oxides is given. 
There are only two which are of interest to the agriculturist, namely, 

CONSISTING OP 

Iron. Oxygen. Symbol. Colour. 

The first oxide* . . 77-23 22-77 Fe Of Black 
The second oxide . 69-34 30-66 FcaOg Red. 

* The first is also called the prot-oxide, the second either the sesqui, or more usually the 
per oxide of iron, 

t Iron is represented by the Bymbol Fe, the initial letters of its Latin name (ferrum). 



THE OXIDES or IRON. 211 

Both of these ex st abundantly in nature, and are present to a greater 
or less extent in all soils. The second or per-oxide, however, is by far 
the most abundant on the earth's surface, and (he reddish colour obser- 
vable in so many soils is principally due to the presence of this oxide. 

The first oxide rarely occurs in the soil except in a state of combina- 
tion with some acid substance, — and so strong is its tendency to combine 
with more oxygen, tliat when exposed to the air, even in a state of com- 
hinalioi3, it rapidly absorbs this element from the atmosphere and 
changes into per-oxide. This change is observable in all chalybeate 
springs, in vi^hich, as they rise to the surface, the iron is generally held 
in solution in the state of the first oxide. After a brief exposure to the 
air, more oxygen is absorbed, and a reddish pellicle is formed on the 
surface, which gradually falls and coats the channel along which the 
water runs, with a reddish sediment of insoluble per-oxide. 

Both oxides are insoluble in pure water, and both dissolve in water 
containing acids in solution. The first oxide, however, dissolves in 
much greater quantity in the same weight of acid, and it is the com- 
pounds of this oxide which are usually present in the soil, and which, in 
bogsy lands, prove so injurious to vegetation.* 

The second oj'.ide possesses two properties which, in connection with 
practical agriculture, are not void of some degree of importance. 

1°. In a soil which contains much vegetable matter in a state of de- 
cay, the per-oxide is frequently deprived of one-third of its oxygen by 
the carbonaceous matter.f and is thus converted into the first oxide 
which readily dissolves in any of the acid substances with which it may 
be in contact. In this state of combination it is more or less soluble in 
water, and in some localities may be brought to the roots of plants in 
such quantity as to prove injurious to their growth. 

2°. The red oxide of iron is said, like alumina (p. 197), to have the 
property of absorbing ammonia, and probably other gaseous substances 
and vapours, from the atmosphere and from the soil. In that which 
occurs in nature, either in the soil or near the surface of mineral veins, 
traces of ammonia can generally be detected. Since then ammonia is 
so beneficial — according to some so indispensably necessary — to vegeta- 
lion, the property which the per-oxide of iron possesses of retaining this 
ammonia when it would otherwise escape from the soil, or of absorbing 
it from the atmosphere, and thus bringing it within the reach of plants, 
must also be indirectly favourable to vegetation — where the soil contains 
it in any considerable quantity. 

An important practical precept is also to be drawn from these two pro- 
perties of this oxide. A red irony soil, to which manure is added, 
should be frequently turned over, an-d should be kept loose and pervious 
to the air, in order thai the formation of prot-oxide (first oxide) may be 

• "That layer of soil (snys Sprenf el), is always especially rich in iron, over which the heel 
of the plough glides in preparing the land. The friction of the soil continually rubs oflF par- 
ticles of iron, which absorb oxygen and change into i\\e Jirst oxide. Hence this part of the 
fioil is always darker in colour than the rest; hence also the reason why tbe soil after /ieep 
ploughing, remains unproductive sometimes for several years." — Chemie, I., p. 428. While 
we admit that the presence of the first oxide of iron in the subsoil affects its fertility, when 
brought to the surface, we may doubt whether much of that iron can have been derived 
from the tear and wear of the plough. 

t The carbon of the vegetable matter comb'mesi with the oxygen ofthe oxide lo form car- 
bonic acid. — ^See p. 63. 



212 SULPHURETS, AND SULPHATES OF IRON. 

prevented as much as possible ; and it may occasionally be summer- 
fallowed with advantage, in order also that the per-oxide may absorb 
from the air those volatile substances which are likely to prove benefi- 
cial to the growth of the future crops. 

2°. Sulphurets of Iron. — Iron occurs in nature combined with sulphur 
in two proportions, forming a sulphuret and a ii-sulphuret. These 

consist respectively — 

Iron. Sulphur. Symbol. 

The sulphuret . . . 62-77 37-23 Fe S 

The bi-sulphuret of . 45-74 54-26 Fe S3 

and are both tasteless and insoluble in water. 

1°. The first of these, the sulphuret (Fe S), occurs occasionally in 
boggy and marshy soils, in which salts of iron exist, or into which they 
are carried by rains or springs. It is notitself directly injurious to vege- 
tation, but when exposed to the air it absorbs oxygen and forms sulphate 
of iron, which, when present in sufficient quantity, is eminently so.* 

2°. The bi-sulphuret, or common iron pyrites (Fe So), is exceedingly 
abundant in nature. It occurs in nearly all rocky formations — and in 
most soils. It abounds in coal, and is the source of the sulphurous smell 
which many varieties emit while burning. It generally presents itself 
in masses of a yellow colour and metallic lustre, more or less perfectly 
crystallized in cubical forms, so brittle and hard as to strike fire with 
steel, and of a specific gravity four and a half times greater than that of 
water (Sp. gr. 4, 5). When heated in close vessels it parts with nearly 
one-half of its sulphur, and hence is often distilled for the sulphur it 
yields. 

In the air it absorbs oxygen, in some cases — as in the waste coal 
heaps — with such rapidity as to heat, take fire, and burn. By (his ab- 
sorption of oxygen (oxidation), sulphuric acid and sulphate of iron are 
produced. In the alum shales the iron pyrites abounds, and these are 
often burned for the purpose of converting the sulphur and sulphuric 
acid for the subsequent manufacture of alum. 

3°. Sulphates of Iron. — Of the sulphates of iron which are known, 
there is only one— the common green vitriol of ihe shops — that occurs in 
the soil in any considerable quantity. There are few soils, perhaps, in 
which its presence may not be detected, though it is in bogs and marshy 
places that it is most generally and most abundantly met with. It is 
often exceedingly injurious to vegetation in such localities, but it is de- 
composed by quick-lime, by chalk, and by all varieties of marl, and 
thus its noxious effects may in general be entirely prevented. To soils 
which abound in lime, it may even be applied with a beneficial effect. 

When a solution of this salt is exposed to the air it speedily becomes 
covered with a pellicle of a yellow ochrey colour, which afterwards falls 
as a yellow sediment. This sediment consists of j^tfr-oxide of iron, con- 
taining a little sulphuric acid; but by the separation of this oxide the 
sulphuric acid is left in excess in the solution, which becomes sour, and 

* Yet in small quantity it may be beneficial. Thus Sprengel mentions that the subsoil of 
a moor near Hanover, which contains some of this sulphuret of iron, produces astonishing 
effects when laid as a top-dressing on the grass lands. The explanation of this is, that the 
pyrites absorb oxygen and is converted into sulphate, and thus re-produces Uie remarkable 
eflfects observed on the addition of gypsum, of suJphuric acid, or of sulphate of soda, to simi-> 
lar grass lands. 



CARBONATES OF IRON, OXIDES AND SALTS OF MANGANESE. Sl3 

Still more injurious to vegetation than before. In boggy places the 
waters impregnated with iron are generally more or less in this acid 
state, and lime, chalk, and marl, with perfect drainage, are the only 
available means by which such lands can be sweetened and rendered 
fertile. 

When iron pyrites is exposed to the air it slowly absorbs oxygen, and is 
converted into sulphate of iron and sulphuric acid ; on the other hand, the 
sour solution above mentioned, when placed in contact with vegetable 
matter, where the air is excluded, parts with its oxygen to the decaying 
carbonaceous matter, and is again converted into iron pyrites. These 
two opposite processes are both continually in progress in nature, and 
often in the same locality, — the one on the surface, where air is present ; 
the other in the subsoil, where the air is excluded. 

4°. Carbonates of Iron. — When a solution of the sulphate of iron, 
above described, is mixed with one of carbonate of soda, a yellow powder 
falls, which is carbonate of iron. This carbonate is found abundantly in 
nature. It is the state in which the iron exists in the ore {clay-iron ore,) 
from which this metal is so largely extracted in our iron furnaces, and 
in the similar ore often found in the subsoil of boggy places, which is 
distinguished by (he name of bog-iron ore. 

Like the carbonate of lime, it is insoluble in water, but dissolves with 
considerable readiness in water charged with carbonic acid. In this 
state of solution it issues from the earth in most of our chalybeate springs, 
and it is owing to the escape of the excess of carbonic acid from the 
water, when it reaches the open air, that the yellow deposit of carbonate 
of iron more or less speedily falls. 

The carbonate of iron, being insoluble in water, cannot be directly in- 
jurious to vegetation. When exposed to the air it gradually parts with 
its carbonic acid, and is converted into per-oxide of iron. 

The ash of nearly all plants contains a more or less appreciable quan- 
tity of oxide of iron. This may have entered into the roots either in the 
state of soluble sulphate or of carbonate dissolved in carbonic acid, or of 
some other of those numerous soluble compounds of iron with organic 
acids, which may be expected to be occasionally present in the soiL 

XII- manganese: oxides, chlorides, CARBONATES, AND SULPHATES 

OF MANGANESE. 

1°. Manganese is a metal which, in nature, is very frequently asso- 
ciated with iron in its various ores. It also resembles this metal in 
many of its properties. In the metallic state, however, it is not an ob- 
ject of manufacture, nor is it used for any purpose in the arts. 

2°. Oxides of Manganese. — Manganese combines with oxygen in 
several proportions. The first oxide is of a light green colour, the se- 
cond and third are black. The first is not known to occur in nature in 
an uncorabined state, the two others exist abundantly in the common 
ores of manganese, and are extensively diffused, though in small quan- 
tity, through nearly all soils. They are all insoluble in water, but the 
two former dissolve in acids and form salts. Traces of these two oxides 
are also to be detected in the ash of nearly all plants. 

3°. Chloride, Carbonate, and Sulphate of Manganese. — If any of 



214 



COMF09ITIOX OF THE OXIDES AND CHLORIDES. 



these oxides be dissolved in muriatic acid a solution of chloride of man- 
ganese will be obtained. 

If this solution of chloride of manganese be mixed with one of car- 
bonate of soda, a white insoluble powder will fall, which is carbonate of 
maganese. 

If this carbonate be dissolved in diluted sulphuric acid, or if any of 
the oxides be digested in this acid, a solution of sulphate of manganese 
will be formed. 

The carbonate of manganese, and its oxides, will also dissolve, though 
more slowly, in acetic acid (vinegar), and in other organic acids which 
may be present in the soil, and will form with them other soluble 
salts. 

The compounds of manganese exist in plants in much less quantity 
than those of iron; but as its oxides, like those of iron, are insoluble in 
pure water, this metal most likely finds its way into the stale of one 
or other of the soluble compounds above described. 

§ 2. Tabular view of the constitution of the compounds of the inorganic 
elements above described. 

Having in the preceding section briefly described the several compounds 
of the inorganic elements of plants, wliich either enter into the constitution 
of vegetable substances, or are supposed to minister to their growth— it 
may prove useful hereafter, if I exhibit at one view the composition per 
cent, of the various oxides, chlorides, sulphurets, and oxygen-acid salts,* 
to which I have had occasion to direct your attention. 

We shall have occasion to refer to the numbers in the following tables 
in our subsequent calculations. 

1° .-^Oxygen per cent, in the oxides of the inorganic elements. 

Oxygen 
» per cent 

Sulphurous Acid . . . 49*85 

Sulphuric Acid . . . 59*86 

Phosphoiic Acid . . . 56*04 

Potash 16*95 

Soda 25*58 

Lime 28*09 

Magnesia 38*71 



I 



Alumina ..... 

Silica 

Prot-oxide of Iron . . 
Per-oxide of Iron . . . 
Prot-oxide of Manganese 
Sesqui-oxide do. . 
Per-oxide do. . . 



Oxygen 
percent, 
46*70 
51*96 
22*77 
30-66 
22-43 
30*25 
36*64 



2°. — Chlorine or Sulphur per cent, in the chlorides and sulphurets. 



Chloride of Potassinm 

• Sodium 

Calcium 

• Magnesium 

First Chloride of Iron 
Second do. do. 



Chlorine 
per cent. 
47*47 
60*34 
63*38 
73-65 
56-62 
66*19 



Sulphuret of Potassimifi 

— i Sodium 

Calcium . . 

Iron . . . 



Bi-Sulphuret of Iron, 
(Iron Pyrites) . 



Sulphur 
per cent, 
29-11 
40-88 
.44-00 
^•23 

47-08 



* So ealled because the acid they contain has oxygen for one of its constituents. 



COMroSlTlON OF THE SALIXE COMPOUNDS. 



215 



3^. — Co'v position per cent, of the Saline combinations above descrihed. 



Carbonate of Potash 
Bi-carbonate of do. 



Sulphate of 
Nitrate of 
Binoxalate of 
Bitartrate of 
Phosphate of 



do. 

do. 

do. (Sail of sorrel) 

do. (Cream of tarta 

do. 



Bi-phosphale of do. 

Carbonate of Soda (dry) . 

(crystallized) 



Bi-carbonate of Soda 
Nitrate of do. 

Sulphate of do. (dry) 

' '■ - " do. (crystallized) 

Phosphate of do. 
Bi-phosphate of do. 

Carbonate of Lime . 
Sulphate of do. (Gypsum) 
(burned) 



Nitrate of Lime 
Phosphate of Lime (Apatite) 
Bi-phosphale of Lime 
Earth of Bones 

Carbonate of Magnesia 

Bi-carbonate of do. 

Sulphate of do. (lEpsom salts) 

Nitrate of do. 

Phosphate of do. 

Sulphate of Alumina 
Phosphate of do. 

Silicate of Potash (soluble) 
Bi-silicate of do. (do.) 
Silicate of Soda (do.) 

Bi-silicate of do. (do.) 

Silicate of Lime 



Magnesia 
Alumina 



Carbonate of Iron 

Sulphate of do. (crystallized) 



Carbonate of Manganese . 
Sulphate of do. (crystallized) 



Acid. 

31-91 
48-38 
45-93 
53-44 
5-2-64 
70-28 
43-06 
60-20 

41-42 
15-43 

58-58 
63-40 
56-18 
24-85 
53-30 
69-54 

43-71 
46-31 

58-47 
65-54 
45-52 

71-48 
48-45 

51-69 
68-15 
32-40 
72-38 
63-33 

70-07 
67-57 

49-46 
66-19 
59-63 
74-71 
61-85 
69-08 
72-95 

38-63 
31-03 

38-27 
33-20 



Base. 



68-09 
51-62 
54-07 
46-66 
34-29 
24-96 
56-94 
39-80 

58-58 
21-81 
41-42 
36 60 
43-82 
19-38 
46-70 
30-46 

56-29 
32-90 
41-53 
34-46 

54-48 
28-52 
51-55 

48-31 
31-85 
16-70 
27-62 
36-67 

29-93 
32-43 

50-54 
33-81 
40-37 
25-29 
38-15 
30-92 
27-05 

61-37 
27-19 

61-73 
29-54 



Water. 



13-07 
4-76 



62-76 



56-77 



20-79 



50-90 



41-78 



37-26 



216 COMPOSITION OF THE ASH OF WHEAT AND OF BARLEY. 



§ 3. On the relative proportions of the different inorganic compounds 
present in the ash of plants. 

Having thus made you acquainted with the general properties and 
composition of the several compound substances of which the ash of 
plants consists, we now advance to the consideration of the relative pro- 
portions in which these substances exist in the ash of the different kinds 
of plants usually cultivated for food. 

We have seen (p. 178) that different species of plants leave very dif- 
ferent quantities of ash when burned ; — the ash left by diflTerent species 
contains also the above earthy and saline substances in very unlike pro- 
portions. This fact has already been stated generally (p. 180) ; we are 
now to illustrate it more fully, and to show the important practical de- 
ductions to which it leads. 

1. OF THE ASH OF WHEAT. 

According to the analysis of Sprengel, 1000 lbs. of wheat leave 11*77 

lbs., and of wheat straw 35*18 lbs. of ash, consisting of — 

Grain of Straw of 

Wheat. Wheat. 

Potash 2*25 lbs. 0*20 lbs. 

Soda 2-40 0-29 

Lime 0*96 2-40 

Magnesia 0-90 0*32 

Alumina, with a trace of Iron 0*26 0*90 

Silica 4-00 28*70 

Sulphuric Acid .... 0-50 0*37 

Phosphoric Acid .... 0*40 1*70 

Chlorine 0*10 0*30 



11*77 lbs. 35*18 lbs. 
If the produce of a field be at the rate per acre of 25 b.ushels of 
wheat, each 60 lbs,, and if the straw* be equal to twice the weight of 
the grain, the quantity of each reaped per acre will be 

Grain . . . 1500 lbs. ) ^ ■, mc u u i 

Straw . . . 3000 lbs. I ^'"""^ ^ P'"^"^^ "^~^ bushels; 

so that the quantity of the different inorganic compounds carried off from 
die soil of each acre will be, in the grain i more than is represented in 
the second column, and in the straw 3 times as much as is represented 
in the third column. 

II. — OF THE ASH OF BARLEY. 

A thousand pounds of the grain of barley (two-rowed, hordeum disti- 
chon,) leave 23i lbs., and of the ripe dry straw 52*42 lbs. of ash. This ash 
consists of— 

* The proportion of the afraw to the seed in grain of all kinds is very variable. In wheat 
it is said to average twice the weight of the grain, but it is very often, even in heavy crops, 
3 to 3X times that weight. 



OF THE ASH OF OATS. 217 

Grain. Straw. 

Potash 2-78 lbs. 1-80 lbs. 

Soda 2-90 0-48 

Lime 1-06 5-54 

Magnesia ..... 1-80 0-76 

Alumina ..... 0-25 1-46 

Oxide of Iron. . . . a trace. 0-14 

Oxide of Manganese . — 0*20 

Silica 11-82 38-56 

Sulphuric Acid . . . 0-59 1-18 

Phosphoric Acid . . 2-10 1-60 

Chlorine 0^19 0-70 



- 23-49 lbs. 52-42 lbs. 
If the produce of a crop of barley amount to 38 bushels of 63 lbs. each 
per acre, and the straw exceed the grain in weight one-sixth, the weight 
of each reaped per acre will be about 

2000 lbs. of grain, 7 ^ i r oo u u i 

2300 lbs. of straw, I ^^«"^ ^ P^°^"^^ ^^ ^^ ^"^^^^^ ' 
and the inorganic matters carried off from the soil by each will be ob* 
tained by multiplying those contained in the second column (above) by 
2, and in the third by 2^. 

III. — OF THE ASH OF OATS. 

In 1000 lbs. of the grain of the oat are contained about 26 lbs., and of 
the dry straw about 57^ lbs. of inorganic matter, consisting of — 

Grain. Straw. 

Potash ...... 1-50 lbs. 8-70 lbs. 

Soda 1-32 0-02 

Lime 0-86 1*52 

Magnesia ..... 0-67 0-22 

Alumina 0-14 0-06 

Oxide of Iron .... 0-40 0-02 

Oxide of Manganese . 000 0-02 

Silica 19-76 45-88 

Sulphuric Acid ... 35 0-79 

Phosphoric Acid . . . 0-70 0-12 

Chlorine . . . . . 0-10 0-05 



25-80 lbs. 57-40 lbs. 

If an acre of land yield 50 bushels, each 54 lbs., of oats, and two-thirds* 

more in weight of straw, there will be reaped per acre, 

Of grain 2-250 lbs., ) ^ j rcn u i, i 

r\p * o-^ cr. 11 } from a produce of 50 bushels; 
Of straw 3750 lbs., ^ ^ 

and the weight of the inorganic matters carried off will be equal to 2i 

times the quantities contained in the second column, and 3| times those 

contained in the third column. 

* Of all kinds of grain, the oat gives the most variable proportion of straw, that which is 
obtained at one time, and in one locality, being two or three times greater than that reaped 
in another. 



Sl'8 



ASH OP RYt, BEANS, PEAS, A]SD VETCHES. 



IV. OP THE ASH OP RYE. 

The weight of ash contained in 1000 lbs. of the grain of rye is lOi lbs.« 
and of the straw 28 lbs. This ash consists of 

Grain. Straw, 

Potash I r: oo iv.« 5 0-32 lbs. 

Soda I ^'^-^^^' \o-n 

Lime 1-22 1-78 

Magnesia 1-78 0-12 

Alumina 0*24 ) ^ or 

Oxide of Iron .... 0-42 ^ 

Oxide of Manganese . 0*34 — 

Silica 1-64 22-97 

Sulphuric Acid . . . 0-23 1-70 

Phosphoric Acid . . 0*46 0*51 

Chlorine 0-09 0-17 



10-40 lbs. 27-93 lbs. 
Rye is remarkable for the quantity of straw it yields, which is often 
from 3 to 4 times the weight of the grain. The return in grain reaches 
about the same average as that of wheat. From an acre of land yield- 
ing a crop of 25 bushels, each 54 lbs., there would be reaped 

Of grain 1350 lbs. ; of straw 4000 lbs. ; 
the whole weight of inorganic matters contained in which is equal to *- 
more than is represented in the second column, added to 4 times the weights 
contained in the third column. 



V. — OP THE ASH OP BEANS, PEAS, AND VETCHES. 

The ash of the seed and straw of the field bean, the field pea, and the 
common vetch {vicia sativa,) dried in the air, contains in 1000 lbs. the 
several inorganic compounds in the following proportions : 





FIBLD 


BEAN. 


FIELD PEA. 


COMMON 


VETCH. 




Seed. 


Straw. 


Seed. 


Straw. 


Seed. 


Straw. 


Potash .... 


4-15 


16-56 


8-10 


2-35 


8-97 


18-10 


Soda 


8-16 


0-50 


7-39 


— 


6-22 


0-52 


Lime .... 


1-65 


6-24 


0-58 


27-30 


1-60 


19-55 


Magnesia . . . 


1-58 


2-09 


1-36 


3-42 


1-42 


3-24 


Alumina . . . 


0-34 


0-10 


0-20 


0-60 


0-22 


0-15 


Oxide of Iron . . 


— 


0-07 


0-10 


0-20 


0-09 


0-09 


Oxide of Manganese 


— 


0-05 


—. 


0-07 


0-05 


0-08 


Silica .... 


1-26 


2-20 


4-10 


9-96 


2-00 


4-42 


Sulphuric Acid 


0-89 


0-34 


0-53 


3-37 


0-50 


1-22 


Phosphoric Acid . 


2-92 


2-26 


1-90 


2-40 


1-40 


2-80 


Chlorine . . . 


0-41 


0-80 


0-38 


0-04 


0-43 


0-84 



21-36 31-21 24-64 49-71 22-90 51-01 
On comparing the numbers in these columns, we cannot fail to remark,-^ 
1°. How much potash there is in the straw of the bean and the vetch. 
'2°. That while there is only a trace of soda in any of the three straws, 
tHere is a considerable quantity in all the seeds. 



ASH or THE TURMP, CARROT, PARSMP, AND POTATO. 



219 



3^. How large a proportion of lime exists in the straw of the pea and 
of the vetch — compared with that of the bean— and how much larger the 
proportion is in all the straws than in any of the grains — and 

4'^. That the quantity of silica in pea straw is double of what is con- 
tained in the straw of the vetch, and 4 times that of the bean straw. 

The produce of straw from these three varieties of pulse is very bulky, 
but varies in weight from 1 to If tons — or is on an average about 2300 
lbs. per acre. The produce of grain is still more variable. 

The bean gives from 16 to 40 bushels, of about 63 lbs. 

The pea . . 12 to 84 '* " 64 lbs. 

The vetch . . 16 to 40 *' ♦' 66 lbs. 

The mean return from beans is estimated by Schwertz [Anleitung 
Zum Praktischen Ackerbau, II., p. 346,] at 25 bushels (1600 lbs.), from 
peas at 15 bushels (1000 lbs.), and from vetches at 17 bushels (1100 
lbs.) per acre. 

The quantity of the several inorganic matters, therefore, carried off 
from an acre in the straw of these crops, will be about 2^ times the 
■weights given in the table — and in the grains, where the crop is near 
the above average, 1| times the weights in the tables for beans and for 
peas, and for vetches very nearly the actual weights above given. 

VI.— OF THE ASH OF THE TURNIP, CARROT, PARSNIP, AND POTATO. 

These four roots, as they are carried from the field, contain respective 
]y in ten thousand pounds — 





TURNIP. 

A 


CARROT. 


PARSNIP. 


POTATO. 




r 

Roots. 


■ n 
Leaves. 






Roots. 


Tops- 


Potash . . . 


23-86 


32-3 


35-33 


20-79 


40-28 


81-9 


Soda .... 


10-48 


22-2 


9-22 


7-02 


23-34 


0-9 


Lime .... 


7-52 


62-0 


6-57 


4-68 


3-31 


129-7 


Magnesia . . . 


2-54 


5-9 


■ 3-84 


2-70 


3-24 


17-0 


Alumina . . . 


0-36 


0-3 


0-39 


0-24 


0-50 


0-4 


Oxide of Iron . . 


0-32 


1-7 


0-33 


0-05 


0-32 


0-2 


Oxide of Manganese 


— 


— 


0-60 


— 


— 


' — 


Silica .... 


3-88 


12-8 


1-37 


1-62 


0-84 


49-4 


Sulphuric Acid . 


8-01 


25-2 


2-70 


1-92 


5-40 


4-2 


Phosphoric Acid . 


3-67 


9-8 


5-14 


1-00 


4-01 


19-7 


Chlorine . . . 


2-39 


8-7 


0-70 


1-78 


1-60 


5-0 



63-03 180-9 66-19 41-80 82-83 308-4 

These roots, as already Stated (note, p. 178), contain very much water, 
so that, in a dry state, ihe proportion of inorganic matter present in them 
is very much greater than is represented by the above numbers. I 
have, however, given the quantities contained in the crop as it is carried 
from the field, as alone likely to be of practical utility. 

The crops of these several roots vary very much in different localities, 
being in some places twice and even thrice as much as in others— every 
nine tons, however, which are carried off' the ground, contain about 
twice the weight of saline and earthy matters indicated by the numbenj 
In the table. 



320 ASH or THE grasses and clovers. 

Vir. OF THE ASH OF THE GRASSES AND CLOVERS. 

The following table might have been much enlarged. 1 have 
ihoiight it necessary, however, to introduce in this place only those 
species of grass and clover which are in most extensivfe use. I have 
also calculated the weights given below, for these plants in the state of 
hay only, as the succulency of the grasses, — that is, the quantity of wa- 
ter contained in the green crop, — varies so much that no correct esti- 
mate could be made of the quantity of inorganic matter present in hay 
or grass, from a knowledge of its weight in the green state only : 





Rye Gras.s 


Red 


White 








Hay. 


Clover. 


Clover. 


Lucerne. 


Sainfoin. 


Potash .... 


8-81 


19-95 


31 05 


13-40 


20-57 


Soda 


3-94 


5-29 


5-79 


6-16 


4-37 


Lime .... 


7-34 


27-80 


23-48 


48-31 


21-95 


Magnesia . . 


0-90 


3-33 


3-05 


3-48 


2-88 


Alumina . . 


0-31 


0-14 


1-90 


0-30 


0-66 


Oxide of Iron . 


— 


— . 


0-63 


0-30 


— 


Oxide of Manganese 


— 


— 


-_ 


— 


— 


Silica .... 


27-72 


3-61 


14-73 


3-30 


5-00 


Sulphuric acid . 


3-53 


4-47 


3-53 


4-04 


3-41 


Phosphoric acid . 


0-25 


6-57 


5-05 


13-07 


9-16 


Chlorine .... 


0-06 


3-62 


2-11 


3-18 


1-57? 



52-86 74-78 91-32 95-53 69-57 

The above quantities are contained in a thousand pounds of the dry 
hay of each plant. 

On comparing the numbers opposite to potash, lime, magnesia, alu- 
mina, silica, and phosphoric acid, we see very striking differences in 
the quantities of these substances contained in equal weights of the 
above different kinds of hay. These differences lead to very important 
practical inferences in reference, — 

1°. To the kind of soil in which each will grow most luxuriantly. 

2°. To the artificial means by which the growth of each may be pro- 
moted — in so far as this growth depends upon the supply of inorganic 
food to the growing plant. 

3°. To the feeding properties of each, and to the kind of stock they 
are severally most fitted to nourish. 

To these and other important practical deductions suggested by the 
above tabulated analyses — as well as by those previously given — of the 
inorganic matters contained in the several varieties of vegetable produc- 
tions usually raised for food, we shall hereafter have frequent occasion 
to revert. In the mean time, a preliminary inquiry demands our at- 
tention, which we shall proceed to consider in the following section. 

§ 4. To what extent do the crops jnost usually cultivated, exhaust the soil 
of inorganic vegetable food? 

A bare inspection of the tabular results exhibited in the preceding 
section gives but a faint idea of the extent to which the inorganic ele- 
mentsu-y bodies are necessarily withdrawn from the soil in the ordinary 
course of cropping. 



EFFECT bf A tkREE tEAtL^' bdufefe^ 6^ CftOPPlNG. 2SI 

I. Let us Consider the effect upon the soil of a still too common three 
years' course of cropping— /aZ^ow, wheat, oats.* If the produce of such 
a course be 25 bushels of wheat and 50 bushels of oats, there would be 
carried from the soil every three years in pounds — 

WHEAT. OATS. 

^ ». ^ , >■ , Total. 

Grain. Straw. Grain. Straw. 

Potash .... 3-3 0-6 3-75 327 4035 

Soda 3-5 0-9 3-3 — 7-7 

Lime 1-5 7-2 2-5 5 7 l6-9 

Magnesia. ... 1-5 1-0 1-7 0-8 5-0 

Oxide of Iron . . — — I'O — 1-0 

Silica 6-0 86-0 500 172-0 314-0 

Sulphuric Acid . . 0-75 1-0 0-9 3-0 5-65 

Phosphoric Acid . 0-6 5-0 1-43 0-5 7-53 

398-13 

The gross weight carried off' in these crops is large — amounting to 
about 400 lbs. It will vary, however, with the kind of wheat and oats 
which are grown, and may often be greater than this. — [See the follow- 
ing section (§5) of the present Lecture.] The greatest portion of the 
matter carried off*, however — upwards of three-fourths of the whole — 
consists of silica; the rest of the materials are equal to 
60 lbs. of dry pearl-ash, 
36 lbs. of the common soda of the shops, 
28 lbs. of bone-dust, 
12 lbs. of gypsum, 
5 lbs. of quick-lime, 

5 lbs. of magnesia, — or for the last three may be substi- 
tuted 33 lbs. of common Epsom salts and 17 lbs. of quick-lime. 

The form in which the silica may be restored to the soil in a state in 
which the plant can absorb it, will be considered hereafter. 

Though large as a whole, the weight of each of the ingredients, taken 
singly, is not great; and yet it is not difficult to understand that if a 
constant drain be kept up on the soil year after year, and the practical 
farming adopted is of such a kind as not to restore to the soil a due pro- 
portion oi each of the substances carried off'— the time must come when, 
under ordinary circumstances, the soil will no longer be able to supply 
the demands of a healthy and luxuriant vegetation. 

II. Let us next consider the effect of a four-years' course system in 
withdrawing these inorganic substances from the soil. And for this 
purpose let us adopt one suited to the lighter soils — as to that of Norfolk — 
turnips, barley, clover and rye grass, wheat. 

Let the crop of turnips aniount to 25 tons of roots per acre, of barley to 
38 bushels, of clover and rye grass each to one ton of hay, and of wheat 
as before to 25 bushels. Then we have from the entire rotation io 
pounds — 

* Common, among other counties, in that of Durham. There are cases, however, in 
which this three years' course may not be indefensible, and it never could be compared with 
some of the so-called improved rotations in East Lothian in the time of Lord Kames ; as for 
instance, /a//oM3, barley, clover, manure on the cloveir stubble, then wheat, bartey, oofs.— See 
The Gentleman Farmer (1802), p. 147. 



222 EFFECT OF A POUR-TEARS' COURSE. 

BARLEY. WHEAT. 

Tumip . « . Red Rye , • . Total. 

Roots. Grain. Straw. Clover. Grass. Grain. Straw. 

Potash 145-5 5-6 45 45-0 285 3-3 0-6 233-0 

Soda 64-3 58 1-1 120 90 3*5 0-9 96-6 

Lime 45-8 2-1 129 63-0 16-5 1-5 7-2 1490 

Magnesia. . . . 15-5 3-6 ]-8 7-5 2-0 1-5 1-0 32-9 

Alumina .... 2-2 0-5 3-4 0-3 0-8 0-4 2-7 10-3 

Silica 23-6 23-G 90-0 8-0 62-0 6-0 86-0 299-2 

Sulphuric Acid . 49-0 1-2 2-8 10-0 8-0 08 1-0 72-8 

Phosphoric do. . 22-4 4-2 3-7 15-0 0-6 0-6 5-0 51-5 

Chlorine .... 14-5 0-4 1-5 8-0 01 0*2 09 25-6 



970-9* 
On comparing the numbers in the last columti — containing the total 
quantity of matter abstracted — with those contained in the three years' 
rotation (p. 221), we see how very much larger an addition must be 
made to the land every fourth year, if we are to restore to it any thing 
like an equivalent for the inorganic matter carried off". 

It will be especially observed that the quantity of potash, and of soda, 
and indeed of nearly every ingredient except the silica, carried off" in 
this course of cropping, is much greater, even in proportion to the time 
it occupies, than in the three-year shift — and that. nine-tenths of the pot- 
ash and soda withdrawn from the soil are contained in the green crops. 
.. To place the relative effect of the green and corn crops upon the soil 
iii a clearer light, I shall exhibit the several quantities of common and 
artificial salts and manures which it would be necessary to add to each 
acre at the beginning of this rotation, in order to supply the various inor- 
ganic substances about to be taken from the land in the next four years' 
crojjping. These quantities are as follow, in pounds : — 

For the For the 

Total. Green Crops. Corn Crops. 

Dry Pearl-ash 325 316 9 

Crystallized Carbonate of Sodaf 333 290 43 

Common Salt 43 38 5 

Gypsum — 30 — 

Quick-lime 150 100 7 

Epsom Salts 200 150 50 

Alum 83 27 56 

Bone-dust 210 150 60 

"With the exception of the silica, the substances above-named, in the 
quantities given, will replace all the inorganic matters contained in the 
whole crop reared, the turnip tops alone not included. A single glance 
at the second and third columns shows how much greater a proportion 
of all these substances is necessary to return what the green crops have 
taken from the land. 

That the fertility of the soil depends in some considerable degree on 

* This is exclusive of the turnip tops, which I have omitted, from not knowing what pro- 
portion their weight in the green state generally bears to that of the roots. 

t Or for every 100 lbs. of the common carbonate of soda may be substituted 40 lbs. of 
common salt or 60 lbs. of dry nitrate of soda. 



WHY WHEAT PREFERS A HEAVY SOIL. 223 

the quantity of the alkaline and other compounds present in it, there can 
be no question, — since not only do we find extraordinary natural luxuri- 
ance of vegetation wliere some of these happen to be present in the soil, 
but we can often greatly increase the apparent productiveness of our 
fields by spreading such substances over them in sufficient quantity. 

How comes it, then, that the green cro|)S which carry oflT all these 
substances in the greatest quantity by very much, should yet least injure 
the land, — nay, should rather renew and prepare it again for the growth 
of crops of corn ? 

This is one of the most interesting practical questions which can pre- 
sent itself to us in the existing state of theoretical agriculture ; — but it 
would carry us away from our more immediate object, were we prema- 
turely to enter upon the discussion of it in this place. It will hereafter 
demand our especial attention, when we shall have become familiar 
with the nature and origin of soils. 

I ma}' be permitted, however, to draw your attention here for a mo- 
ment — as neither out of place, nor uninteresting, for many reasons, — to 
an opinion expressed by Liebig on the question why wheat prefers stiff 
and clayey soils. " Again," he says, " how does it happen that wheat 
does not flourish in a sandy soil, and that a calcareous soil is also un- 
suitable for its growth, unless it be mixed with a considerable quantity 
of clay ? It is because these soils do not contain alkalies insufficient 
quantity, the growth of wheat being arrested by this circumstance, even 
should all other substances be presented in abundance." — {^Organic 
Chemistry applied to Agriculture, p. 151,] 

Without dwelling on the fact that excellent crops of wheat are reaped 
in some parts of our island from sandy and calcareous* soils — what kind 
of crops, we may ask, can be reared with success on the lighter soils to 
which wheat seems least adapted ? The turnip rejoices in light land, 
and the potato not unfrequently attains the greatest perfection on a sandy 
soil. Yet ten tons of potato roots, or twenty of turnip bulbs, — exclu- 
sive of the tops — contain nearly ten times as much of the two alkalies, 
potash and soda, as fifty bushels of wheat with its straw included. | 
What ground is there, then, for the explanation given by Liebig — of the 
peculiar qualities of the so-called wheat lands ? We might witli far 
greater show of reason assume the converse of his proposition, and infer 
that wheat does not prefer sandy soils, because they are too rich in alkali ! 
It is singular, and would almost seem to strengthen this converse propo- 
sition, that beans, peas, and vetches, which are so often resorted to as a 
good preparative fijr wheat, contain also a much larger quantity of alkali 
than the latter grain. Thus the grain and straw together of twenty-six 
bushels of beans contain 71 lbs., of twenty bushels of peas 26 lbs., and 
of twenty bushels of vetches 74 lbs. of potash and soda taken together. 

As I have already stated, however, we are not yet prepared for dis- 
cussing this very curious and interesting question. 

* On the thin chalk soils of the Yorkshire Wolds a crop of wheat is taken every four or 
five years, yielding an average of 34 or 26 bushels. The rotation is turnips, barley, clover or 
beans, wheat. 

t According to the analyses of Sprengel given in the previous pages, ten tons of potatoes 
contain 143 lbs. of alkalies, twenty tons of turnips 154 lbs., and fifty bushels of wheat wiUi 
its straw only 16 lbs. 



224 ARE THE INORGANIC CONSTITUENTS REALLt CONSTANT ? 



§ 5. Of the alleged constancy of the morganic constituents of plants., in 

hind and quantity. 

In the preceding lecture (ix., p. 177), it was stated that the ash of tlie 
same plant, if ripe and healthy, is nearly the same in kind and quality 
in whatever circumstances (if favourable) of soil and climate it may 
grow. This general observation, however, is consistent with certain 
differences in the above respect, which are not without interest in their 
bearing upon agriculture both in theory and practice. Thus, 

1°. The different parts of the same plant contain quantities of inor- 
ganic matter, not only different in their gross weights, but unlike also in 
the relative proportions of the several substances of which the entire ash 
consists. Both of these points have been previously illustrated (pp. 179, 
180), and they are placed in the clearest light by the tabulated analyses 
introduced info the preceding section. 

2°. The quantity and relative proportions of the different inorganic 
substances also vary with the season of the year at which the examina- 
tion is made. Thus, according to De Saussure, plants of the same wheat 
which a month before flowering left 7-9 per cent, of ash, left when in 
flower only 5*4, and when ripe 3*3 per cent. The quantify of potash 
in the potato leaf diminishes very much as the plant approaches to ma- 
turity (MoUerat) — and the same has been observed in many saltworts 
and other sea-side plants. In the young plant of the salsola clavifolia 
there is much potash and no soda, but as its age increases the latter alkali 
appears, and gradually takes the place of the former.* 

It is probably true, therefore, of all plants — that the ash both in kind 
and quanfity is affected by the age at which the plant has arrived. It 
would appear that the unlike chemical changes which take place in the 
interior of the plant, at the successive periods of its growth, require the 
presence of different chemical agents — or that the production of new 
parts demands the co-operation of new substances. 

3°. Similar differences are sometimes observed also when the same 
plant is grown in different soils. Thus it is known that the straw of the 
oat grown upon boggy land is very different in colour and lustre, from 
that yielded by the same variety of seed, when grown upon sound and 
solid soU. I lately examined two such portions of straw from the same 
seed — grown on the same farm on the estate of Dunglass, the one on 
boggy, the other on sound stiff land, when the straw from the 
Sound land left 6*64 per cent, of ash, and from the 
Boggy land " 6*2 per cent, of ash; 
while the silica contained in the ash from the 

Sound land amounted to 3*42 per cent., and from the 

Boggy land " to 1*90 per cent, of the weight of the straw. ' 

A remarkable difference, therefore, existed in the relative proportions, 

* Meyen, Jahresbericht, 1839, p. 125. In regard to these salt-loving plants, which generally 
abound in soda, a curious observation was long ago made by Cadet. He states that if a plant 
of common salt- wort (salsola aali) be transplanted into an inland district — and seed from this 
plant be afterwards sown, the second race of plants will contain much potash, but scarcely a 
trace of soda.— Gmelin's Handbuch der Chemie, II. p. 1492. Potash may thus take the 
place of soda for a time, but removed from its native habitat.^ the plant would in a few gene* 
rations die out and diisappear. 



THE ASH TROM WHEAT STRAW IS VARIABLE. 225 

at least of the silica, in these two varieties of straw, and this difference 
can be Attributed only to the unlike nature of the soils in which the two 
samples were grown. But on boggy soils the oat plant is unhealthy, 
and in general neither fills its ear, nor ripens a perfect seed ; — the dif- 
ference in the ash in this case, therefore, cannot be considered as entirely 
opposed to the general proposition, that in a healthy slate, plants at 
the same period of their growth always yield nearly the same weight 
of ash. 

But that different experimenters have obtained very unlike quantities 
of ash, from the most common cultivated plants, apparently in a state 
of health, when grown under different circumstances of soil and climate, 
— does appear to contradict this general proposition. Thus 100 lbs. of 
ripe wheat straw leave of ash 

4*3 lbs. De Saussure ; 
4-4 lbs. Berthier; 
3'5 lbs. Sprengel ; 
15-5 lbs. Sir H. Davy ; 
while the straw of one variety of red wheat grown on a clay-loam, at 
Aykley Heads, near Durham, gave me 6-6 per cent., and that of two 
other varieties of red wheat, grown near Dalton, in Ravensworth Dale, 
Yorkshire, a country abounding in limestone — and on the same field — 
left respectively 12*15 and 16*5 percent, of ash. The difference of 4 
per cent, between these last two results, shows that the quantity of asli 
depends much upon the variety of grain examined — though to what ex- 
tent all the great differences obtained, as above shown, are to be ascribed 
to this cause alone, it is impossible to say, until numerous other experi- 
ments shall have been instituted. 

One thing, however, is manifest, that the quantities of inorganic mat- 
ter necessarily contained in a crop of wheat, given in a previous page 
(p. 216) on the authority of Sprengel, must be considered as probably 
far below the mean proportion, since some varieties yield, in the form 
of ash, about six times as much as is there stated. 

Every one knows how uncertain general conclusions are, — or expla- 
nations of natural phenomena, — when deduced from single observations 
only, and of this truth the above results present us with a useful illus- 
tration. Thus Liebig, in his Organic Chemistry applied to Agriculture 
p. 152, to which we have had frequent occasion to refer — explains 
why land will refuse to grow wheat, and may yet produce good crops 
of oats or barley in the following manner : — " One hundred parts of the 
stalks of wheat yield 15*5 parts of ashes (H. Davy) : the same quantity 
of the dry stalks of barley 8-54 (Schrader), and one hundred parts of the 
stalks of oats only 4-42. The ashes of all are of the same composition. 
We have in these facts a clear proof of what plants require for their 
growth. Upon the same field which will yield only one harvest of 
wheat, two crops of barley and three of oats may be raised." 

In this passage it has been assumed that the ash of wheat and other 
straws is constant in quantity, that wheat straw always contains much 
more than that of oats or barley, and that the ash is in each case of the 
same composition (see above, pp. 216 to 217), — all of which premises 
being incorrect, the conclusion must of course be rejected. 

But the straw of barley and oats also, according to different authorities, 



226 ASH FROM OAT AND BARLEY STRAW ALSO VARIABLE. 



i 



leaves very unlike quantities of ash. Thus, according to Spren^el and 
Schrader/lOO lbs. of 

Sprengel. Schrader. 

Oat Straw leave . 5-74 lbs. 4-42 lbs. 66 J. 

Barley straw . . 5'24 lbs. 8-54 lbs. 
We cannot help conceding, therefore, generally, in regard to the cereal 
grasses, that different varieties, at least, of the same plant, may contain 
inorganic matter in different jrroportions. 

But certain analyses which have been made seem to demand a still 
further concession. Thus De Saussure found that the ash left by the 
same tree or shrub — by the fir or the juniper for example — differed both 
in kind and in quantity, according as it grew upon a granitic or calca- 
reous soil. Berihier also found the ash of a piece of Norway pine {pi- 
nits abies) to differ very much from that of the wood of the same pine 
grown in France. From these and a few other observations, the con- 
clusion has been ver}'' generally drawn by vegetable physiologists, that 
the ash of plants in general is determined both in kind and quantity by 
the soil in which they grow. 

This is very likely to be true to a certain extent, as we have seen in 
the straw of the bog oat above adverted to, but a sufficient number of 
accurate comparative analyses of the ash of cultivated plants* has not 
yet been published, to enable us to determine the precise mfluence of the 
soil in all cases. It is impossible, however, that the prevailing charac- 
ter of the soil can have more than a general influence on the character of 
the ash of any living vegetable — so long as the plant retains a healthy 
state. The experiments of De Saussure do not appear to have been 
made with sufficient care,f while the only comparative experiment of 
Berthier is open to objections of another kind. 

I have said that the quantity and kind of the ash is likely to beafTected 
by the character of the soil to a certain extent. The following considera- 
tions seem to embody nearly all the sources of such variation, of which 
we can at present speak with any degree of certainty : — 

1°. Plants at different periods of their growth require for the produc- 
tion of their several parts, and therefore appropriate from the soil, differ- 
ent inorganic substances ',% hence the ash will vary with the age of the 
plant. 

• Five samples of the same variety of wheat (Hunter's wheat) grown on different soils in 
the neighbourhood of Haddington, gave me very nearly the same proportions of ash. Thus 
the sample grown on a 

Per cfint. 
1°. Deep reddish clay loam, subsoil gravel, left 1-776 

2<^. Red clay on gravel 1787 

3°. Stiff clay on retentive subsoil 1903 

4°. Light clay on rather retentive subsoil . . 1917 

5°. Light turnip land 1-824 

These results approach very near each other. The differences are perhaps too slight to 
justify us in concluding that the ash is greatest in quantity when the sub.soil is most reten- 
tive. 

t The accuracy of De Saussure's analyses is rendered very doubtful by the fact that, in 
the ash of all the different trees and shrubs he examined, he found a large quantity, in that 
of the juniper as much as 43 per cent, of alumina, and in that of the pine from 12 to 16 per 
cent., while Berthier, whose skill is undisputed, found no alumina in the ash of any of the 
numerous trees on which his experiments were made. 

t This fact indicates an exceedingly interesting field of chemical research in connection 
with practical agriculture. What substance will bring this or that seed into early leaf? — 
what will hasten its growth in middle life?— what will bring it to early maturity 1 The wheat 



SOME SUBSTANCES ACT AS MEDIA OR AGENTS ONLY. 227 

2°. If the substances necessary for the perfection of one or more parts 
of a plant abound in the soil, its chief developement will take the direc- 
tion of those parts. Thus one plant will run to leaf or straw, another to 
flower and seed. Thus also in the grain of one crop of wheat more glu- 
ten is produced than in that of another, and as this gluten appears to 
contain the phosphates of lime and magnesia,. as essential constituents, 
the ash will necessarily vary with the gluten of the seed. 

3°. Some substances appear to enter into the circulation of plants not 
so much as actual and necessary constituents of the parts of the vegetable, 
as to serve as media or agents by which other compounds, both organic 
and inorganic, may be conveyed to the plant. Thus common salt ap- 
pears to enter many plants for the j)urpose of supplying soda, its chlo- 
rine being discharged by the leaf. Silica enters the plant chiefly in the 
form of silicate of potash or soda. When it reaches its proper destina- 
tion — the stalks of the grasses for instance — this silicate is decomposed 
chiefly by the carbonic acid, which is always present in the pores of the 
green stem, the silica is deposited and the alkali proceeds downwards 
with the sap as a soluble carbonate, or in combination with some other 
organic acid. Thus the same portion of alkali may return many times 
into the circulation with this or with other materials which the parts of 
the plant require, and every new burden it deposits will necessarily 
cause a new variation in the relative proportions of the several inorganic 
constituents which are afterwards detected in the ash. 

4°. As the water which enters by the roots always brings with it some 
soluble substances, the quantity of these conveyed into the plant will be 
materially affected by the amount of evaporation from the leaves; and 
hence, after a long drought, the leaves of the turnip, the potato, and 
other plants, will yield a larger proportion of ash than will be obtained 
from them in moist and rainy weather. 

5°. In the mineral kingdom it is found that one substance may not 
unfre(|uently take the place, and perform the functions, of another. Thus 
potash and soda replace each other in certain minerals, as do also lime 
and magnesia and the phosphoric and arsenic acids. It has been sup- 
posed that a similar interchange may take place in the vegetable king- 
dom — that when the plant cannot get potash it will take soda — that 
when it can get neither, it will appropriate lime, — and so on. Such a 
conjectural interchange may possibly take place in a small degree, for a 
limited time, and in certain plants, without materially affecting their ap- 
parent health — but it is not by trusting to such resources of nature that 
a luxuriant vegetation or plentiful crops will ever be reared by the prac- 
tical agriculturist. 

Admitting, however, all these sources of variation in the kind and 
quantity of the ash obtained from different plants, the sound practical 
conclusions from all we know on the subject at present seem to be — 

1°. That certain inorganic substances, in certain proportions, are ne- 
cessary to all plants usually cultivated for food — if they are to be reared 
or maintained in a healthy state. 

\ 
stalk and the potato require more potash while in rapid growth. This growth may be con- 
tinued and prolonged by the presence of ammonia ; while lime is said to bring it sooner to 
a close, and to give an earlier harvest. How valuable would be the multiplication of such 
facts ! 



228 BASIS OF ENLIGHTENED PRACTICAL AGRICULTURE. 



1 



2°. That we must seek for these necessary substances in the inorganic 
constituents which are present in the richest crops of every kind — in the 
produce of the most fertile soils.* 

3°. That where these necessary substances are not present in any 
soil, we may infer that it will prove unfit to yield a luxuriant crop of a 
given kind ; or, on the other hand, where these substances are not to be 
detected in the ash of tlie plant, that the fault of the crop, if any, maybe 
ascribed to their partial or total absence from the soil on which it grew. 

These conclusions form the basis of an enlightened and scientific prac- 
tical agriculture. This basis, however, requires to be strengthened and 
enlarged by further experimental investigations. 

* " I have examined," says Sprengel, " the finest seed-corns from many localities, and I 
have invariably found the quantities not only of the organic substances— starch, sugar, &c. — 
but also of the inorganic compounds in all the celebrated seed-corns, so perfectly alike, that 
one would have thought they had all grown on one and the same soil." — L^hre vom Diinger, 
p. 43. 



LECTURE XL 

Nature and origin of soils— Organic matter in the soil. — General constitution of the earthy 
part of the soil. — Classification of soils from tlieir chemical constituents. — Method of ap- 
proximate analysis for tlie purposes of classification. — General origin of soils and subsoils. 
—Structure of the earth's crust.— Stratified and unstratified rocks. — Crumbling or degra- 
dation of rocks. — Diversity of soils produced. — Superficial accumulations.— Tabular view 
of the character and agricultural capabilities of the soils of the different parts of Great 
Britain. 

Such are the inorganic compounds which minister to the growth of 
plants, and such the proportions in which they severally occur in the 
living vegetable. Whence are these inorganic constituents all derived? 

We have seen that the atmosphere, when pure, contains no inorganic 
matter, and that if dust, spray, or vapours occasionally float in the air, 
and are tarried by the winds to great distances — yet that they are 
only accidentally present, and cannot be regarded as a source from 
which the general vegetation of the globe derives a constant supply of 
those mineral substances which are necessary to its healthy existence. 

The soil on which they grow is the only natural source from which 
their inorganic food can be derived. We are led, therefore, as the next 
subject of our study, to imjuire into the nature and origin of soils.* 

§ 1. Of the organic matter in the soil. 

Soils differ much as regards their immediate origin, their physical 
properties, their chemical constitution, and their agricultural capabili- 
ties; yet all soils which in their existing state are capable of bearing a 
profitable crop, possess one common character — they all contain organic 
matter in a greater or a less proportion. 

This organic matter consists in part of decayed animal, but chiefly of 
decayed vegetable substances, sometimes in brown or black fibrous por- 
tions, exhibiting still, on a careful examination, something of the origi- 
nal structure of the organized substances from which they have been de- 
rived — sometimes forming only a fine brown powder intimately inter- 
mixed with the mineral matters of the soil — sometimes scarcely percep- 
tible in either of those forms, and existing only in the state of organic 
compounds more or less void of^ colour and at times entirely soluble in 
water. In soils which appear to consist only of pure sand, or clay, or 
chalk, organic matter in this latter form may often be detected in con- 
siderable quantity. 

The proportion of organic matter in soils which are naturally produc- 
tive of any useful crops, varies from one-half to 70 per ceiit. of their 
whole weight. With less than the former proportion they will scarcely 
support vegetation — with more than the latter, they require much ad- 
mixture before they can be brought into profitable cultivation. It is 

* On the subject of this and the following lecture, the reader will consult with advantage 
an excellent little work, " On the nature and property of soils," by Mr. John Morton. 

20 



230 PROPORTION OF ORGANIC MATTER IX SOILS. 

only in bog2:y and peaty soils that the latter large proportion is ever 
found — in tlie best soils the organic matter does not average five percent., 
and rarely exceeds ten or twelve. Oats and rye will grow upon land 
containing only one or one and a half per cent. — barley where two or 
three per cent, are present — but good wheat soils contain in general from 
4 to 8 per cent., and, if very stiff and clayey, from 10 to 12 per cent, 
may occasionally be detected. 

Though, however, a certain proportion of organic matter is always 
found in a soil distinguished for its fertility, yet the presence of such sub- 
stances is not alone sufficient to impart fertility to the land. I do not 
allude merely to such as, like peaty soils, contain a very large excess of 
vegetable matter, but to such also as contain only an average proportion. 
Thus of two soils in the same neighbourhood — the one contained 4-05 
per cent, of organic matter, and was very fruitful — the other 4*19 per 
cent., and was almost barren. This fact is consistent with what has been 
stated in the two preceding lectures, in regard to the influence exercised 
by the dead inorganic matter of the soil, on the general health and luxu- 
riance of vegetation. 

» 
§ 2. General constitution of (he earthy part of the soil. 

From what is above stated, it appears that, on a general average, the 
earthy part of the soil in our climate does not constitute less than 96 per 
cent, of its whole weight, when free from water. This earthy part con- 
sists principally of three ingredients: — 

1°. 0{ Silica, siliceous sand, or siliceous gravel — of various degrees 
of fineness, from that of an impalpable powder as it occurs in clay soils, 
lo the large and more or less rounded sandstones of the gravel beds. 

2°. Alumina — generally in the form of clay, but occasionally occur- 
ring in shaly or slaty masses more or less hard, intermingled with the 
soil. 

3°. Lime, or carbonate of lime — in the form of chalk, or of fragments 
more or less large of the various limestones that are met with near the 
surface in different countries. Where cultivation prevails it often hap- 
pens that all the lime which the soil contains has been added to it lor 
agricultural purposes — in the form of quick-lime, of chalk, of shell-sand, 
or of one or other of the numerous varieties of marl which different dis- 
tricts are known to produce. 

It is rare that a superficial covering is anywhere met with on the 
surface of the earth, which consists solely of any one of these three sub- 
stances — a soil, however, is called sandy in which the siliceous sand 
greatly predominates, and calcareous, where, as in some of our chalk 
and limestone districts, carbonate of lime is present in considerable abun- 
dance. When alumina forms a large proportion of the soil, it constitutes 
a clay of greater or less tenacit}-. 

The term clay, however, or pure clay, is never used by writers on 
agriculture to denote a soil consistingof alumina only, for none such ever 
occurs in nature. The Y>^re porcelain clays are the richest in alumina, 
but even when free from water they contain only from 42 to 48 per cent, 
of this earth, with from 52 to 58 of silica. These occur, however, only 
in isolated patches, and never alone form the soil of an>' considerable 



COMPOSITION OF PORCELAIN AND AGRICULTURAL CLAYS. 231 

district. The strongest clay soils vvliich are anywhere in cultivation 
rarel}' contain more than 35 per cent, of alumina.*- 

Soils in general consist in great part of the three substances above 
named in a state o{ mechanical mixture. This is always the case with 
the siliceous sand and with the carbonate of lime — but in the clays the 
silica and the alumina are, for the most part, in a stale of chemical com- 
bination. Thus, if a portion of a stiflT clay soil be kneaded or boiled 
with repeated portions of water till its coherence is entirely destroyed, 
and if the water, with the finer ])arts which float in it, be then poured 
into a second vessel, the whole of the soil will be separated into two por- 
tions — a fine impalpable powder consisting chiefly of clay, poured ofT 
with the water, and a quantity of siliceous or other sand in particles of 
various sizes, which will remain in the first vessel. This sand was 
only mechanically mixed with the soil. The fine clay retains still some 
mechanical admixtures, but consists chiefly of silica and alumina chem- 
ically combined. 

Of the porcelain clays above alluded to, there are several varieties, 
three of which, containing the largest proportion of alumina, consist res- 
pectively -of — 





I. 


11. 


III. 


Silica . , 


. 47-03 


46-92 


46-0 


Alumina . 


. 39-23 


34.81 


40-2 


Water . 


. 13-74 


18-27 


13-8 



100-00 100-00 lOO-Of 
But, as already stated, these clays rarely form a soil — the stiffest 
clays treated by the agriculturist containing a further portion of silica, 
some of which is mechanically mixed, and can be partially separated by 
mechanical means. 

The strongest agricultural clays {pipe-clays) of which trustworthy 
analyses have yet been published, consist, in the dry state, of 56 to 62 
of silica, from 36 to 40 of alumina, 3 or 4 of oxide of iron, and a trace of 
lime. Clays of this composition are distinguished by the foreign agri- 
cultural writers as pure clays. They are all probably made up of some 
of the varieties of porcelain clay, more or less intimately mixed with 
siliceous and ochrey particles — in so minute a slate of division that they 
cannot be separated by the method of decanfation above described. 

These clays are adopted by the German and French writers as a 
standard to which they can liken clay soils in general, and by compari- 
son with which they are enabled distinctly to classify and name them. 
As the use of the term clay in this sense has been introduced into Eng- 

• In an interesting paper on subsoil ploughinfr by Mr. H. S. Thompson, in the report of 
the Yorkshire Agricultural Society for 1837, p. 47, it is stated that the lias clays, which form 
the subsoil in certain parts of Yorkshire, contain sometimes, in the dry state, as much as 54 
per cent, of alumina (?) 

t When heated to redness the whole of the water is driven oflFfrom these clays, and they 
tlien consist respectively of— 

Silica 54 5 57 4 53 4 

Alumina 45-5 42 6 46 6 



1000 1000 100 • 

which numbers are in accordance with those given at the foot of the preceding page. 



232 CLASSIFICATION OF SOILS. 

lish agricultural books,* and as it is really desirable to possess a word to 
which the above meaning can be attached, I shall venture in future to 
era ploy it always strictly in this agricultural sense. 

By alumina, then, I shall in all cases express the pure earth of alum, 
which exists in clays, and to which they ovi'e their tenacity — by clay, a 
finely divided chemical compound, consisting very nearly of 60 of silica 
and 40 of alumina, with a little oxide of iron, and from which no siliceous 
or sandy matter can be sejJarated mechanically or by decantation. 

Of this clay the eartliy part of all known soils is made up by mere 
mechanical admixture with the other earthy constituents (sand and 
lime), in variable proportions. On a knowledge of these proportions the 
following general classification and nomenclature are founded. 

§ 3. Of the classification of soils from their chemical constituents. 

Upon the principles above described soils may be classified as fol- 
lows : — 

1°. Pure clay (pipe-clay) consisting of about 60 of silica and 40 of 
alumina and oxide of iron, for the most part chemically combined. It 
allows no siliceous sand to subside when diffused through water, and 
rarely forms any extent of soil. 

2°. Strongest clay soil (tile-clay, unctuous clay) consists of pure clay 
mixed with 5 to 15 per cent, of a siliceous sand, which can be separated 
from it by boiling and decantation. 

3°. Clay loam differs from a clay soil, in allowing from 15 to 30 per 
cent, of fine sand to be separated from it by washing, as above described. 
By this admixture of sand, its parts are mechanically separated, and 
hence its freer and more friable nature. 

4°. A loamy soil deposits from 30 to 60 per cent, of sand by mechani- 
cal washing. 

5°. A sandy loam leaves from 60 to 90 per cent, of sand, and 

6°. A sandy soil contains no more than 10 per cent, of pure clay. 

The mode of examining with the view of naming soils, as above, is 
very simple. It is only necessary to spread a weighed quantity of the 
soil in a thin layer upon writing paper, and to dry it for an hour or two in 
an oven or upon a hot plate, the heat of which is not sufficient to dis- 
colour the paper — the loss of weight gives the water it contained. While 
this is drying, a second weighed portion may be boiled or otherwise 
thoroughly incorporated with water, and the whole then poured into a 
vessel, in which the heavy sandy parts are allowed to subside until the 
fine clay is beginning to settle also. This point must be carefully 
watched, the liquid then poured off, the sand collected, dried as before 
upon paper, and again weighed. This weight is the quantity of sand 
in the known weight o( moist soil, which by the previous experiment has 
been found to contain a certain quantity of water. 

Thus, suppose two portions, each 200 grs., are weighed, and the one 
in the oven loses 50 grs. of water, and the other leaves 60 grs. of sand, 
— then, the 200 grs. oi moist are equal to 150 oi dry, and this 150 of dry 

* As in British Husbandry, p. 113, and in Loudori's Encyclopedia of Agriculture, p. 315, 
where classifications of soils are given chiefly from Von Thaer, though neitiier work ex- 
hibits with sutficient prominence the meaning to be attached to ag^ricuitural day, as distin- 
guished from alumina, sometimes called pure clay by the chemist. 



MARLY A>JD CALCAREOUS SOILS, AND VEGETABLE MOULDS. 233 

soil contain 60 of sand, or 40 in 100 (40 per cent.) It would, tjierefore, 
be properly called a loam, or loamy soil. 

But the above classification has reference only to the clay and sand, 
while we know that lime is an important constituent of soils, of which 
they are seldom entirely destitute. We have, therefore, 

7°. Marly soils, in which the proportion of lime is more than 5 but 
does not exceed 20 per cent, of the whole weight of the dry soil. The 
marl is a sandy, loamy, or clay marl, according as the proportion of 
clay it contains would jilace it under the one oroiher denomination, sup- 
posing it to be entirely free from lime, or not to contain more than 5 per 
cent., and 

8°. Calcareous soils, in which the lime exceeding20 per cent, becomes 
the distinguishing constituent. These are also calcareous clays, calca- 
reous loams, or calcareous sands, according to the proportion of clay and 
sand which are present in them. 

The determination of the lime also, when it exceeds 5 per cent., is 
attended with no difficulty. 

To 100 grs. of the dry soil diffused through half a pint of cold water, 
and half a wine-glass full of muriatic acid (the spiritof salt of the shops), 
stir it occasionally during the day, and let it stand over-night to settle. 
Pour off'the clear liquor in the morning and fill up the vessel with water, 
to wash away the excess of acid. When the water is again clear, pour 
it off", dry the soil and weigh it — the loss will amount generally to about 
one per cent, more than the quantity of lime present. The result will 
be sufficiently near, however, for the purposes of classification. If the 
loss exceed 5 grs. from 100 of the dry soil, it may be classed among the 
marls, if more than 20 grs. among the calcareous soils. 

Lastly, vegetable matter is sometimes the characteristic of a soil, 
which gives rise to a further division of 

9°. Vegetable moulds, which are of various kinds, from the garden 
mould, which contains from 5 to 10 percent., to the peaty soil, in which 
the organic matter may amount to 60 or 70. These soils also are clayey, 
loamy, or sandy, according to the predominant character of the earthy 
admixtures. 

The method of determining the amount of vegetable matter for the 
purposes of classification, is to dry the soil well in an oven, and weigh 
it; then to heat it to dull redness over a lamp or a bright fire till the 
combustible matter is burned away. The loss on again weighing is the 
quantity of organic matter. 

Summary. — The several steps, therefore, to be taken in examining a 
soil with the view of so far determining its constitution as to be able pre- 
cisely to name and classify it, will be best taken in the following order: — 

1°. Weigh 100 grains of the soil, spread them in a thin layer upon 
white paper, and place them for some hours in an oven or other hot 
place, the heat of which may be raised till it only does not discolour the 
paper. The loss is water. 

2°. Let it now (after drying and weighing) be burned over the fire as 
above described. The second loss is organic, chiefly vegetable matter, 
with a little water, which still remained in the soil after drying. 

3°. After being thus burned, let it be put into half a pint of water 

i 



234 SUMMARY OK THE METHOD OF EXAMIA AT10?f . 

with half a wine-glass full of spirit of salt, and frequently stirred. 
"When minute bubbles of air cease to rise from the soil on settling, this 
process may be considered as at an end. The loss by this treatnient 
will be a little more than the true per centage of lime,* and it will gen- 
erally be nearer the truth if that portion of soil be employed which has 
been previously heated to redness. 

4°. A fresh portion of the soil, perhaps 200 grs. in its moist state, may 
now be taken and washed to determine the (juantity of siliceous sand it 
contains. If the residual sand be supposed to contain calcareous matter 
its amount may readily be determined by treating the dried sand with 
diluted muriatic acid, in the same way as when determining the whole 
amount of lime (3°.) contained in the unwashed soil.f 

Let me illustrate this by an example. 

Example. — Along the outcrop of some of the upper beds of the green 
sand in Berkshire, Wiltshire, and Hampshire, and probably also in 
Buckingham and Bedford, occur patches of a loose friable grey soil 
mixed with occasional fragments of flint, which is noted for producing 
excellent crops of wheat every other year. It is known in the valley of 
Kingsclere, at Wantage, and Newbury. I select a portion of this soil 
from the latter locality for my present illustration. 

1°. After being dried in the air, and by keeping some time in paper, it 
was exposed for some hours to a temperature sufficient to give the white 
paper below it a scarcely perceptible tinge : by this process 104^ grs. 
lost 4 grs. 

2°. When thus dried, it was heated to dull redness. It first black- 
ened, and then gradually assumed a pale brick colour, the change, of 
course, beginning at the edges. The loss by this process was 4i grs. 

3°. After this heating, it was put into half a pint of pure rain water 
with half a wine-glass full of spirit of salt. After some hours, when the 
action had ceased, the soil was washed and dried again at a dull red 
heat. The loss amounted to 3 grs. 

The soil, therefore, contained 

Water 4 grs. 

Organic matter (less than) . . 4^ 
Carbonate of lime (less than) . 3 

Clay and sand 93^ 

104i 
4°. By boiling and washing with water, 291 grs. of the undried soil 
left 202i grs. of very fine sand chiefly siliceous, — 104i, therefore, would 
have left 73 grs., or the soil contained per cent. — 

' A more rigorous method of determining the lime when less than 5 per cent, will be 
given in the following lecture. 

t The weighings for the purposes here described may be made in a small balance with 
grain weights, sold by the druggists for 5s. or 6.s., and the vegetable matter may be burned 
aw^ay on a slip of sheet iron or in an untinned iron tablespoon over a bright cinder or char- 
coal fire — care being taken that no scale of oxide, which may be formed on the iron, be al- 
lowed to mix with the soil when cold, and thus lo increase its weigh'. Those who are in- 
dined to perform the latter operation more neatly, may obtain for about 6s. each — from the 
dealers in chemical apparatus — lliin light platinum capsules from I to IX inches in dianne- 
ter, capable of holding 100 grs. of soil — and for a few shillings more a spirit lamp, over 
which the vegetable matter of the soil may be burned away. With care, one of these little 
capsules will serve a life- time. 



1 



DIFFERKNCK BETWKKN SOIL AMD SUBSOIL. 235 

Water 3-9 per cent. 

Organic niatler (less than) . . 4*1 

Carbonate of lime (less than) . 3-0 

Clay 19-0 

Sand (very fine) 70.0 

100-0* 
This soil, therefore, containing 70 per cent- of sand, separable by 
decantation, is property a sandy loam. 

§ 4. Of the distinguishing characters of soils and subsoils. 

Beneath the immediate surface soil, througli which the plough makes 
its way, and to which the seed is entrusted, lies what is commonly dis- 
tinguished by the name of subsoil. This subsoil occasionally consists 
of a mixture of the general constituents of soils naturall}'^ different from 
(hat which forms the surface layer — as when clay above has a sandy 
bed below, or a light soil on the surface rests on a retentive clay beneath. 

This, however, is not always the case. The peculiar characters of 
the soil and subsoil often result from the slow operation of natural causes. 

In a mass of loose ni.atter of considerable depth, spread over an extent 
<jf country, it is easy to understand how— even though originally alike 
through its whole mass — a few inches at the surface should gradually 
acquire different physical and chemical characters from the rest, and 
how there should thus be gradually established important agricultural 
distinctions between the first 12 or 1.5 inches (the soil), the next 15 (the 
subsoil), and the remaining body of the mass, which, lying still lower, 
does not come under the observation of the practical agriculturist. 

On the surface, plants grow and die. Through the first few inches 
their roots penetrate, and in the same the dead plants are buried. This 
portion, therefore, by degrees, assumes a brown colour, more or less dark, 
according to the quantity of vegetable matter which has been permitted 
to accumulate in it. Into the subsoil, however, the roots rarely pene- 
trate, and the dead plants are still more rarely buried at so great a depth. 
Still this inferior layer is not wholly destitute of vegetable or other or- 
ganic matter. However comparatively impervious it may be, still water 
makes its way through it, more or less, and carries down soluble organic 
substances^ which are continually in the act of being produced during the 
decay of the vegetable matter lying above. Thus, though not sensibly 
discoloured by an admixture of decayed roots and stems, the subsoil in 
reality contains an appreciable quantity of organic matter which may 
be distinctly estimated. 

Again, the continual descent of the rains upon the surface soil washes 
down the carbonates of lime, iron, and magnesia, asw^ell as other soluble 
earthy substances — it even, by degrees, carries down the fine clay also, 

* Some of these numbers differ by a minute fraction from those in the preceding page : 
this is because they are calculated from the more correct decimal fractions contained in my 
own note-book. The organic matter is said to be less than the number here given, because 
by simple drying, as here prescribed, the whole of the water cannot be driven off— a portion 
being always retained by the clay, which is not entirely expelled, till the soil is raised nearly 
to a red heat. Hence the loss by this second heating must always be greater than the actual 
weiiiht of organic matter present. The lime is also less than the number given, because, as 
already stated, the acid dissolves a little alumina as well as any carbonate of magnesia which 
may be present. 



336 HOW THE SUBSOIL IS PRODUCED. 

SO as gradually to establish a more or less manifest difference between 
the upper and lower layers, in reference even to the earthy ingredients 
which they respectively contain. 

But, except in the case of very porous rocks or accumulations of earthy 
matter, these surface waters rarely descend to any great depth, and hence 
after sinking through a variable thickness of subsoil, we come, in gene- 
ral, to earthy layers, in which little vegetable matter can be detected, 
and to which the lime, iron, and magnesia of the superficial covering 
has never been able to descend. 

Thus the character of the soil is, that it contains more brown organic, 
chiefly vegetable, matter, in a state of decay — of the subsoil, that ihe or- 
ganic matter is less in quantity and has entered it chiefly in a soluble 
state, and that earthy matters are present in it which have been washed 
out of the superior soil — and of the subjacent mass, that it has remained 
nearly unaffected by the changes which vegetation, culture, and atmos- 
pheric agents have produced upon the portions that lie above it. 

From what is here stated, the effect of trench and subsoil ploughing, 
in altering more or less materially the proportions of the earthy constitu- 
ents in the surface soil, will be in some measure apparent. That which 
the long action of rains and frosts has caused to sink beyond the ordinary 
reach of the plough is, by such methods, brought again to the surface. 
When the substances thus brought up are directly beneficial to vegeta- 
tion or are fitted to improve the texture of the soil, its fertility is increased. 
Where the contrary is the case, its productive capabilities may for a 
longer or a shorter period be manifestly diminished. 

§ 5. On the general origin of soils. 

On many parts of the earth's surface the naked rocks appear ov6r 
considerable tracts of country, without any covering of loose mate- 
rials from which a soil can be formed. This is especially the case in 
mountainous and granitic districts, and in the neighbourhood of active 
or extinct volcanoes, where, as in Sicily, streams of naked lava stretch 
in long black lines amid the surrounding verdure. 

But over the greater portion of our islands and continents the rocks 
are covered by accumulations, more or less deep, of loose materials — 
sands, gravels, and clays chiefly — the upper layer of which is more or 
less susceptible of cultivation, and is found to reward the exertions of 
human industry with crops of corn in greater or less abundance. 

This superficial covering of loose materials varies from a few inches (o 
one or two hundred feet in depth, and is occasionally observed to consist 
of different layers or beds, placed one over the other — such as a bed of 
clay over one of gravel or sand, and a loamy bed under or over both. 
In such cases the characters and capabilities of the soil must depend 
upon which of these layers may chance to be uppermost — and its char- 
acter may often be beneficially altered by a judicious admixture with 
portions of the subjacent layers. 

It is often observed, where naked rocks present themselves, either in 
cliffs or on more level parts of the earth, that the action of the rains and 
frosts causes their surfaces gradually to shiver off*, crumble down, or 
wear away. Hence at the base of cliffs loose matter collects — on com- 
paratively level surfaces the crumbling of the rock gradually forms a soil— 



CRUMBLING OR DECUADATION OF ROCKS. 237 

while from those which are sufficiently inclined the rains wash away 
?he loose materials as soon as they are separated, and carry them down 
to the valhes. 

The superficial accumulations of which we have spoken, as covering 
the roci<s in many places to a depth of one or two hundred feet, consist 
of materials thus washed down or otherwise transported — by water, bv 
winds, or by other geological agents. Much of these heaps of transported 
matter is in the state of too fine a powder to permit us to say from whence 
it has been derived — but fragments of greater or less size are always to 
be found, even among the clays and fine sands, which are sufficient to 
point out to the skilful geologist the direction from which the whole has 
been brought, and often the very rocks from which the entire accumula- 
tions have been derived. 

Thus the general conclusion is fairly drawn, that the earthy matter of 
all soils has been produced by the gradual decay, degradation, or crumb- 
ling down of previously existing rocks. It is evident therefore — 

1°. That whenever a soil rests immediately upon the rock from which 
it has been derived, it may be expected to partake more or less of the 
composition and characters of that rock. 

2°. That where the soil forms only the surface layer of a considerable 
depth of transported materials, it may have no relation whatever either 
in n;ineralogical characters or in chemical constitution to the immedi- 
ately subjacent rocks. 

The soils of Great Britain are divisible into two such classes. In 
some counties an acquaintance with the prevailing rock of the district 
enables us to predict the general characters and quality of the soil ; in 
others — and nearly all our coal fields are in this case — the general 
character and capabilities of the soil have no relation whatever to the 
rocks on which the loose materials rest. 

§ 6. On the general structure of the earth's crust. 

Beneath the soil, and the loose or drifted matters on which it rests, we 
everywhere find the solid rock. This rock in most countries is seen — 
in mines, quarries, and cliffs — to consist of beds or layers of varied thick- 
ness placed one over the other. To these layers geologists give the 
name of strata; and hence rocks which are thus made up of many se- 
parate layers are called stratified rocks. 

But in some places entire mountain masses are met with, in which no 
parting into layers or beds is seen, but which appear to consist of one 
unbroken rock of the same material from their upper surface down- 
wards, and often as far beneath as we have been able to penetrate into 
the earth. Such rocks are said to be unstratified. Among these are 
included the granites, the trap, green-stone, or basaltic rocks, and the 
lavas. Geologists have ascertained that all these unstratified rocks have, 
like the volcanic lavas, been in a more or less perfectly melted state — 
that their ])resent appearance is owing to the action of fire — and hence 
they are often called igneous* rocks. They often also exhibit a more or 
less crystalline or glassy structure, or contain, imbedded in them, nu- 
merous regular crystals of mineral substances ; hence they are some- 
limes called also crystalline rocks. The terms igneous, crystalline, and 



Sometimes pyrogenous, produced by fire ; but this is an unnecessarily hard word. 



I 



238 



STRATIFIED AM) UNSTaATlFIED liOCK8. 



unstratified, therefore, apply to the same class of rocks — fhe first uiJica- 
ling their origin, the second their structure iw the stnall, the third their 
structure in the large, as distinguished from that of the rocks which occur 
in beds. 

The following diagram exhibits tfie general appearance of the strati- 
fied rocks as they are found to occur in contact with unstratified masses 
in various parts of the globe : — 




A represents an unstratified mountain mass or other similar rock rising 
up through the stratified deposits. The heiiditig up of the edges of the 
latter indicates that after the beds were deposited in a nearly level posi- 
tion, the mass A was intruded or forced up through them, carrying the 
broken edges of the beds along wiih it. 

B shows the more quiet way in which veins or dykes of unstratified 
green-stone, or trap, or lava, cut through the beds without materially 
displacing them — as if when in a fluid state it had risen up and filled a 
previously existing crack or chasm. In Devonshire, in the North of 
Scotland, and in Ireland, the granite rises in many places exactly as is 
shown at A, and nearly all our coal fields exhibit in their whin dykes 
numerous illustrations of what is shown at B. 

C and D exhibit the n)anner in which the strata overlie one anoilier 
in nearly a horizontal position — 1, 2, 3, indicating diHTereni kinds of rock, 
— as a lime-stone, a sand-stone, and a clay — wliich again are subdivided 
into beds or thinner layers, by the partings exhibited in the woi)d-cut. 

The stratified rocks lie sometimes nearly level or horizontal over large 
tracts of country — as in the above diagram, — sometimes they are more 
or less inclined or appear to dip in one and to rise in the opf)Osite direc- 
tion — as if a surface, formerly level, had been pushed down at the one 
end and raised up at the other, — and sometimes they seem to rest entire- 
ly upon their edges. Upon the mode in which tiiey thus lie, the urufor^ 
mity of the soil, in a district where it reposes immediately on the rocks 
from which it is derived, is materially dependent. In the following dia-^l 
gram the surface from A to E represents a tract of couDtry in which the ■ 




rocks have in different parts these diflferent degrees of inclination, at A 
vertical, at B more inclined, and from C to E nearly horizontal. Now, 
it is obvious that if the outer surface of these several rocks crumble and 
form a soil which rests where it is produced — then the quality of the soil 
on every spot will be determined by the nature of the rock beneath. 
Hence, in proceeding from E over the comparatively level strata, we 
shall find the soil pretty uniform iu quality till we come to the edge of 



VERTICAL, INCLINED, AND HORIZONTAL STRATA. 239 

the bed D, thence it will again be nnifonn, though perhaps tlitferent from 
the former, till we reach the stratum C, when again it will prove uni- 
form over a considerable space till we be^in lo climb the hill to B. So 
the whole hill-side in ascending to B will be of one and the same kind 
of soil. But as we descend on ihe other side and pass B, we get upon 
the edges of the beds, and then as we proceed from one bed lo another, 
the quality of the soil may vary every few yards, more or less, ac- 
cording as the members of this group of beds are more or less differ- 
ent from each other. But when we ascend the hill to A, where the 
beds, besides being vertical, are also very thin, the soil may change at 
almost every step, provided — which is, however, rarely the case among 
the rocks (slate rocks) which occur most frequently in this position — pro- 
vided the mineralogieal characters of the several vertical layers be sen- 
sibly unlike. Such dissimilarities in the angular position of the strata, 
as are represented in the above diagram, are of constant occurrence, not 
only in our islands, but in all parts of the globe ; and they illustrate very 
clearly one important natural cause of that want of uniformity in the na- 
ture and capabilities of the soil which is more or less observable in every 
undulating and in some comparatively level countries also. 

It may be stated, as the general result of an extended examination 
of all the stratified rocks yet known — that they consist of alternations or 
admixtures of three kinds of rock only — of sand-stones, of lime-stones, 
and of clays. The sand-stones are of various degrees of solidity and 
hardness, from the loose sand of some parts of the lower new-red and 
green-sand formations, to the almost perfect quartz rock not unfrequently 
associated with the oldest strata. The lime-stones vary in like manner 
from the soft chalk to the hard mountain lime-stone and the crystalline 
statuary marble ; while the clays are found of all degrees of hardness 
from that of the London and Kimmeridge clays, which soften in water, 
to that of the roofing slates of Cumberland and Wales, — and even to 
that of the gneiss rocks which rest immediately upon the granite, and 
which appear to be only the oldest clays altered by the action of heat. 

But the stratified rocks, though thus distinguishable into three main 
varieties — rarely consist of any one of these substances in an unmixed 
slate. The sand-stones not unfrequently contain a little clay or lime, 
while the lime-stones and clays are often mixed with sand and with 
each other. 

If the stratified rocks thus consist essentially of these three substances, 
the soils formed from them by natural crumbling or decay must have a 
similar composition. A sandy soil will be formed from a sand-stone,— 
a calcareous soil from a lime-stone, — a clay from a slate or shale, — and 
from a mixed rock, a soil containing a mixture of two or more of these 
earthy ingredients — in proportions which will depend upon the relative 
quantities of each which are contained in the rock from which they have 
been derived. 

§ 7. Relative positions and peculiar characters of the several strata. 

1°. The several strata, or series of strata, which present themselves 
in the crust of the globe, always maintain the same relative positions. 
Thus the numbers 3, 2, 1, in the annexed diagram, represent three series 
of beds known by the names of the magnesian lime-stone, the lower new- 



240 THESE STRATA ARE OFTEN CONTINUOUS OVER LARGE AREAS. 




red sand-slone, and ihe cuul-nieasures, lying over each other in iheir 
natural positions — ilie lime-stone uppermost, the sand-stone next, and 
the coal beneath both. Whenever these three rocks are met with, near 
each other, they always occupy the same relative position, the coal 
never appears above this lime-stone, and the sand-stone, if present, is 
always between the two other series of beds. The same is true of every 
other group of strata — the order in which they are placed over each other 
is universally the same. 

2°. These beds are generally continuous also over very large areas — 
or are found to stretch, without interruption, over a great extent of coun- 
try. Hence when they dip beneath other beds, as they are seen to do 
in the above diagrams, we can still, with a high degree of probability, 
infer their presence at a greater or less depth, wherever we observe on 
the surface those other beds which are known usually to lie immediate- 
ly above them. Thus, if in a tract of country consisting of the magne- 
sian lime-stone (3) above-mentioned, it is known that deep vallies occur, 
it becomes probable that the soil in those vallies will rest upon, and may 
be formed from, the underlying red sand-stones or coal-measures; and 
that it will therefore possess very different agricultural capabilities from 
the soil that generally prevails around it. Or in chalk districts, beneath 
which usually lies the green-sand, the presence of a deep valley cutting 
through the chalk almost necessarily implies in the hollow a very differ- 
ent soil from that which is cultivated in the chalk wolds above. This is 
the case in the valley of Kingsclere, where the peculiar wheat soil oc- 
curs, of which an approximate analysis has been given in page 234. 

3°. It has been already slated that the stratified rocks, though so very 
numerous and so varied in appearance, yet consist generally of repeated 
alternations of lime-stones, sand-stones, and clays, or of mixtures of two 
or more of these earthy substances. But the several series of strata are 
nevertheless distinguished from each other by peculiar and often well- 
marked characters. 

Thus some are soft, crumble readil3% and soon form a soil, — while 
others, though consisting of the same ingredients, long refuse to break 
into minute fragments, and thus condemn the surface of the country 
where they occur to more or less partial barrenness. 

In others, again, the proportions of sand or lime are so varied, from 
bed to bed, that the character of the mixture in each is entirely different 
— so that while one, on crumbling down, will give a stiff* clay, another 
will produce a loam, and a third a sandy marl. 

Or, in some rocks the remains of vegetables are present in considera- 
ble quantity, — as in the neighbourhood of our coal-beds — or the bones or 
shells of animals in greater or less abundance, by each of which the 
agricultural characters and capabilities of the soils formed from them, 
will be more or less extensively affected. 

Or lastly, the mixture of other earthy substances gives a peculiar 



THEIR PECULIAR CHARACTERS ALSO CONTINUOUS. 241 

character to many rocks. Thus tlie per-oxide of iron, which imparts 
their red colour to many strata— as to the red sandstones — influences 
not only the mineralogical character of the rock, but also the quality of 
the soil which is formed by its decay. In like manner the presence of 
magnesia, sometimes in large quantity, in many lime-stones, })roduce9 
an important modification in the chemical constitution and mineralogical 
characters of the rock, as well as in its relations to practical agriculture. 

In consequence of these and other similar causes of diversity, if not 
every stratum, at least every series of strata, exhibits disiinguishing and 
characteristic peculiarities, by means of which it may be more or less 
readily recognized. On these peculiarities the special agricultural ca- 
pabilities of those parts of the globe in which each series of beds occurs 
are in a great degree dependent. 

4". This peculiar character is also more or less continuous over very 
large areas. Thus if a given stratum be found on the surface in any 
part of England, and again in any part of Russia, the soil formed from 
that bed will generally exhibit very nearly the same qualities in both 
countries. A knowledge of the geology, therefore, — that is, of the kind 
of rock which appears on the surface in every part of a country — ena- 
bles us to predict generally the kind of soil which ought to rest upon it, 
if it be not covered by foreigii accumulations ; while, on the other hand, 
a knowledge of the agricultural capabilities of any one district in which 
certain rocks are known to lie immediately beneath the soil, and of the 
agricultural practice suited to that district, will indicate the probable ca- 
pabilities of any other tract in which the same kind of rock is known to 
appear on the surface, and of the kind of culture which may be most 
successfully applied to it. 

It is evident, then, that a familiar acquaintance with the general 
characters and relative positions of all the series of strata that have hith- 
erto been observed, and of the classification of rocks considered geologi- 
cally, to which this knowledge has led, must be fitted to throw much 
light upon the principles of a general, enlightened, and philosophical 
agriculture. 

§ 8. Classification of the stratified rocks, their extent, and the agricultU' 
ral relations of the soils derived from them. 

It is a received principle, I may say rather, an obvious fact, that in 
the crust of the earth, as in the walls of a building, those layers which lie 
lowest or undermost have been first deposited, or are the oldest. In re- 
ference to this their relative age, the stratified rocks are divided into the 
primary, the first deposited and most ancient — the secondary, which are 
next in order — and the tertiary, which overlie both. 

These three series of strata are again subdivided into systems, and 
these into minor groups, called formations, — the several members of 
each system and formation having such a common resemblance, either 
in mineralogical character or in the kind of animal and vegetable re- 
mains found in them, as to show that they were deposited under very 
nearly the same general physical conditions of the globe. 

The following table exhibits the names, relative positions, thicknesses, 
and mineralogical characters of ihe stratified rocks, in descending order, 
as they occur in our islands. The annexed remarks indicate also the 



242 CLASSIFICATION OF THE STRATIFIED ROCKS. 

districts where each of these groups of rocks forms the surface, and the 
general agricultural character of the soils that rest upon them. 

I. Tertiary Strata — characterized by containing, among other fos- 
sils, the remains of animals, which are identical with existing species. 

NAME AND THICKNESS. MINERALOGICAL CHARACTERS. 

1°. Crat^. bQ ft, A mass of rolled pebbles mixed with 

marine shells — resting on beds of sand 
and sandy lime-stone ; the whole more 
or less impregnated with oxide of iron. 
Extent. — The Crag forms a stripe of land a few miles in width in the east- 
em part of Norfolk and Suffolk, and in the south-eastern part of the latter coun- 
ty. It is a flat, and generally, it is said, a fertile arable district. 

2°. Fresh-water Marls. 100 ft. Marls and marly lime-stones, with 

fresh-water shells divided into two se- 
ries by an estuary deposit, containing 
marine shells. 
Extent. — On these beds reposes the soil of the northern half of the Isle of 

Wio-ht, the only part of England in which they appear at the surface. 

3°. London Clay. 200 to 500 ft. Stiff, almost impervious, brown, blue, 

and blackish clay, rich in marine shells, 
and containing layers of lime-stone no- 
dules. 
Extent. — The gi-eater part of the county of Middlesex, the south-eastern 
half of Essex, and the southern half of Hampshire, rest upon the London Clay. 
Soil. — The soil is naturally strong, heavy, wet, and tenacious, "sticking to 
the plough like pitch," and shrinking and cracking in dry weather. Where it 
is mixed with sand, it foniis a fertile loam ; and hence where the sand of the 
subjacent plastic clay is easily accessible, it may readily be improved by ad- 
mixture. Repeated dressings of London manure convert it into rich meadow 
land, and even where this cannot be obtained, the difficulty and expense of cul- 
ture have caused a very large portion of it to be retained in pasture. That 
wliich is under culture is said to be too strong for turnips and barley, but to 
grow excellent crops of wheat and beans. 

4°. Plastic Clay. 300 to AOO ft. Alternating beds of clay and sand, of 

various colours, and thicknesses. Some 
of the beds of clay are pure white, and 
so fine as to be used for making pipes. 

Extent. — This formation surrounds the London clay with an indented, gen- 
erally low, and flat belt, of vaiy ing breadth, occupying a large space in Hamp- 
shire and Dorset, in Essex, Suffolk, and Norfolk, — stretching along the north- 
ern part of Kent and Surrey, and throwing out arms into Berks, Buckingham, 
and Hertford. 

Soil. — The soil is very various, tlie alternate beds of sand and clay of differ- 
ent qualities producing soils of the most unlike quality often within very short 
distances. The greatest portion of this tract is in arable culture, but there are 
extensive heaths and wastes in Berks, Hampshire, and Dorset. 

In Norfolk and Suffolk, where the lower beds of this sand rest upon chalk, 
the soil is readily changed, by an admixture with this chalk, into a good sandy 
loam, which will yield large crops of turnips, barley, and wheat, instead of the 
heath and bent, its sole original produce. This chalking is generally repeated 
once in 8 years, at an expense of 50s. an acre. In Hampshire and Berkshire, 
the same method is adopted with great success, and the rich crops now reaped 
from Hounslow Heath ai-e the result of this method of improvement. 



SOIL or THE UPPER AND LOWER CHALKS. 243 

II. The Secondary Strata — contain no animal remains which 
can be identified with existing species. Those which are found in them 
are nearly all different from those which occur either in the tertiary 
above or the primary strata below. 

A. — Cretaceous System. 

5°. Chalk. 600 ft. The upper part softer, and contain- 

ing layers of flints, with many marine 
remains. Below, the chalk is harder, 
and towards the bottom passes into 
beds of marl — (chalk marl). 
Extent. — The chalk occupies a very large area in the south-eastern part of 
the island. It forms a broad band of from 15 to 25 miles in breadth, running 
north-east and south-west from the extreme south-western part of Dorset, to 
the extreme north of Norfolk, — it there turns nearly at a right angle, into the 
centre of Lincolnshire, where it is 10 to 15 miles in breadth, and thence stretches 
into Yorkshire, in the south-eastern part of which county it covers a large area, 
and about Flamborough Head attains a breadth of 25 miles. In passing 
through Berkshire and Surrey, it is partially inten-upted by the plastic clay 
which it embraces on every side; and hence, in following the outline of this for- 
mation it encircles with a broad fringe the southern edges of Sussex and Surrey 
and the northern borders of Kent. 

Soil. — The soils fomied from the upper chalk are all more or less mixed 
with flints, and they produce naturally a very short but excellent sheep pasture. 
A great portion of this chalk-land in Dorset, Wilts, and Berks, has been occu- 
pied as a sheep-walk for ages, though under proper cultivation it is said to be 
convertible into good arable land, producing barley, turnips, wheat, and sain- 
foin. The lower chalk soils (chalk marl) consist of a deep, strong, calcareous 
grey or white loam, very productive, and when mixed with the green sand be- 
low it, becoming still richer, more friable, and more productive of every kind of 
crop. It is better suited for wheat than the upper chalk, but is less adapted for 
turnips. 

The porous nature of the chalk renders the soil very dr)'^, and in many locali- 
ties the only method of obtaining a sufficient supply of water is by forming 
ponds to catch and retain the rain-water. 

In Norfolk and SuflTolk, on the Lincolnshire, and more recently on the York- 
shire Wolds, great miprovement has been effected by dressing the chalk-soil 
with fresh chalk brought up from a considerable depth below, and laid on at the 
rate of 50 to 80 cubic yards per acre. The explanation of this procedure is to 
be found in the fact above staled, that the lower chalk marls, without flints, pro- 
duce an excellent soil, fitted therefore, by admixtiu-e with the poorer upper-chalk 
soils, for materially improving their quality. It is, therefore, only in localities 
where this lower chalk can be obtained, that the above method, of improve- 
ment can be with any material advantage adopted. This is proved by the 
practice at Sudbury, in Suffolk, which rests upon the upper beds, where it is 
found to be more profitable to import the lower chalk from Kent, to lay upon 
these lands, than to dress them with any of the chalks (only upper beds) which 
are immediately within their reach.* 

6°. Green Sand. bOO ft. The upper beds consist of layers of 

a Upper, 100. a greenish sand or sand-stone, often 

b Gault, 150. chalky. The gault is a solid compact 

c Lower, 250. mass of an impervious blue clay, some- 
times marly. The lower green sand 
contains a series of ochrey resting on a 

• A rigorous chemical analysis of characteristic specimens of these two chalks might lead 
to interesting results. 



244 UPPER GREEN SAND, WEALDEN, AND UPPER OOLITE ROCKS. 

series of greenish sandy strata. The 
whole of these beds are in many places 
full of fossils. 

Extent. — The Green Sand forms a naiTow border round the whole of the 
northern and western edge of the chalk, except in Yorkshire, where it has not ' 
as yet been anywhere discovered at the surface. It skirts also the southern 
edge of the chalk in Sun-ey and Kent, and its eastern boundaiy in Hampshire, 
where it attains a breadth of eight or ten miles. It forms likewise the southern 
portion of the Isle of Wight. 

Soil. — The upper beds, which are the gi-eenest and most chalky, form an 
open friable soil, easily worked, and of the most productive character. It con- 
sists in general of an exceedingly fine sand, mixed with more or less of clay 
and calcareous matter (see analysis, p. 234), coloured by greenish gi'ains. It is 
rich and productive of every species of crop, and the peculiar richness of this 
soil has been remarked not only in England but also in the United States of 
Nortli America. In some parts of Bedfordshire the soils of this formation form 
the most productive garden lands in the kingdom. In other localities, again, 
where tlie soil is formed from layers of black or of white silvery sand, it produ- 
ces naturally nothing but heath. 

The impervious gault clay fonns in Cambridge and Huntingdon '•' a thin, 
co4d clay soil, which, when wet, becomes as sticky as glue, is most expensive 
to cultivate as arable land, and naturally produces a poor, coarse pasture." 
Much of this tract, though unenclosed, is yet generally in arable culture, under 
two crops and a naked fallow — the enclosed parts are chiefly in pasture, and 
yield a rich herbage. 

The lower gi'een-sand presents itself over a comparatively small surface, 
is in some localities (Sussex) laden with ii'on ochre, and is there naturally un- 
productive. 

B. — Oolitic System. 

7^. Wealden. QoO/f. The upper part consists of a fi-esh- 

a Weald Clay, 300. water deposit of brown, blue, or fawn- 

d Hastings Sand, 400. coloured clay, often marly and almost 

c Purbeck lime-stone, 250. always close and impei-vious to water. 

Beneath this are the iron or ochrey 
Hastings sands, which again rest upon 
the Purbeck beds of alternate fresh- wa- 
ter lime-stones and marls. 
Extent. — The Wealden rocks appear at the suiface only in Sussex and 
Kent, of which they form the entire central portion. 

Soil. — The soil formed from the Weald Clay is fine grained and unctuous — 
often pale coloured. £md containing much fine grained siliceous sand. It forms a 
paste which dries and hardens almost like a brick, so that the roots of plants 
cannot penetrate it. From the expense of cultivating such land, much of it 
is in wood (Tilgate Forest), and some is in poor wet pasttire. On the whole 
of this tract, therefore, there is much room for improvement. The Hastings 
sands produce a poor brown sandy loam which naturally yields only heath and 
brush-wood. Much of this soil i? in pastiu"e, but, under proper cultivation, it 
yields good crops of all kinds. Where the ruins of tlie Purbeck marls are in- 
termixed with it, the soil is of a superior quality. 

8°. Upper Oolite. GQOft. The upper part of this formation con- 

a Portland Beds 100. sists of the oolite* limestones and gal- 

b Kimmeridge Clay, 500. careous sand-stones long worked at 

Portland— the lower of the blue slaty 

• So Darned because they consist of small c^g-shaped granules, like the roe of a fish. 



IMPERVIOUS SOIL OF THE OXFORD CLAY. 245 

or greyish, often calcareous and bitu- 
minous beds of the Kimmeridge clay. 

ExTE^fT. — The Upper Oolite runs norih-east along the northern edge of 
the green sand, from the western extremity of Dorset to the extreme north of 
Norfolk. It is in general only 2 or 3 miles, but in a few places expands to 
6 or 8 miles in breadth. It appears again on the western edge of the green 
sand in Lincolnshire, and in Yorkshire forms a stripe 5 or 6 miles in breadth, 
which crosses the country from Hebnsley to Filey Bay. In the Isle of Port- 
land also it is found, and it stretches in a narrow stripe along part of the south 
coast of Dorset. 

Soil. — The soil from the Portland rocks, in consequence of the prevalence 
of siliceous and the absence of clayey matter, produces naturally, or when laid 
down to grass, only a poor and benty herbage. Its loose aiTd sandy nature 
makes it also very cheap to work, and hence it is chiefly in arable culture. It 
is easily affected by drought, but in damp seasons it produces abundant crops 
— especially in those parts where the soil is naturally mixed with the detiitus 
of the over-lying Hastings sand, and of the calcareous Purbeck beds. 

The Kimmeridge clay forms a tough, greyish, impervious, often however 
very calcareous soil and subsoil. From the difficulty of working it, much of 
the surface over which this formation extends is laid down to grass, and the old 
pasture land afibrds excellent herbage. The celebrated pasture lands of the vale 
of North Wilts rests partly on this clay. The relative thicknesses of the Portland 
beds and the Kimmeridge clay will readily account for the fact of this clay be- 
ing spread over by far the greatest part of the area occupied by this formation. 
In Yorkshire, clay of a gi-eat thickness is the only member of this series that 
has hitherto been obsei-ved. On this, as well as on the subjacent Oxford clay, 
the judicious investment of capital might produce a much greater annual breadth 
of corn. 

^° . Middle Oolite. 500 ft. The uppennost bed in this foi-mation 

Upper Calcareous Grit, ) is a sand-stone containing a consider- 

Coral Rag, > 100. able quantity of lime — next is a coral- 

Calcareous Grit, ) line lime-stone (coral rag) resting upon 

Oxford Clay, ) other sand-stones, which contain much 

Kelloways Rock, V 400. ihne in their upper and little or none in 

Blue Clay ' S their lower beds. Below these is an 

enormous deposit of adhesive tenacious 
dark blue clay, frequently ceilcareous 
and bituminous, and towards the lower 
part containing irregular beds of sand- 
stones and lime-stones(Kelloways rock) 
beneath which the clay again recurs. 
Extent. — The middle adjoins the upper oolite on the north and west — ac- 
companying it from the extremity of Dorset, into Wilts, Oxford, Huntingdon, 
Lincolnshire, and Yorkshire. Until it reaches Huntingdon, it rarely exceeds 
6 or 8 miles in width, but in this county and in Lincoln it expands to a width 
of nearly 20 miles. In Yorkshire it nearly surrounds the vipper oolite, and 
on the northern border of the latter formation attains a width from north to 
south of 6 or 8 miles. 

Soil. — The higher beds of both the upper and lower calcareous grits produce 
good land. They contain lime intermingled with the other materials of the 
siliceous sand-stone. The upper calcareous grits are no doubt improved by 
their proximity to the Kimmerido"e clay above them, while the lower calcareous 
grit is in like manner benefitted by the lime of the super-incumbent coral rag. 
The under beds of both groups are the more gritty, and foiTn a poor, baiTcn, 
almost worthless soil, much of which in Yorkshire is still imreclaimed. 
Upon the hills of the coral rag itself occurs the best pasture which is met with 



246 ARABLE LANDS OF THE OOLITE. 

in that part ofthe North Riding of Yorkshire through which this fonnation 
extends. 

The Oxford clay, which is by far the most important member of this forma- 
tion, and forms the surface over by far the largest portion of the area occupied 
by it — produces a close, heavy, compact clay soil, difficult to work, and which 
is one of the most expensive of all the clays to cultivate. This is especially 
the case in Bedford, Huntingdon, Northampton, and Lincoln, in which coun- 
ties, neveriheless, a considerable extent of it is under the plough. Jn Wilts, 
Oxford, and Gloucester, it is chiefly in pastvire, and as over these districts it as- 
smues the character rather of a clayey loam, the herbage is thick and luxuriant. 
The impervious nature of this clay has caused the stagnation of water upon 
its lower lying portions, the consequent accimiulation of vegetable matter, and 
the formation of bogs. The extensive fens of Lincoln, Northampton, Hunt- 
ingdon. Cambridge, and Norfolk, rest upon the Oxford clay. This tract of 
fenny country is 70 miles in length, and about 10 in average breadth. When 
drained and covered with the clay from beneath, it is capable of being converted 
into a most productive soil. In Lincolnshire, there are about a million acres 
of fen, which have their drainage into the Wash, about 50,000 of which are at 
present in-eclaimable, on account ofthe state ofthe outlet. 

In the neighbourhood of the Kelloways rock tlie clay becomes more loamy 
and less difficult to work. 

Both in Yorkshire and in the southern distiicts, the Oxford clay is found to 
favour the growth of the oak, and hence it is often distinguished by the name 
ofthe oak tree clay. 

10°. Inferior Oolite. 600 ft. Thin, Impure, rubbly beds of shelly 

a Combrash, 30. lime-stone form the upper part of this 

b Forest Marble, 50. series. These rest upon alternate beds 

c Bradford Clay, 50. of oolitic shelly lime-stone and sand- 

d Bath Oolite, 130. stone, more or less calcareous, having 

e Fuller's Earth, 140. partings of clay ; these again upon beds 

/ Inferior Oolite, ) nr^n of blue marly clay, immediately under 

g Calcareous Sand, \ which are the thick beds of the light-co- 

loured oolite lime-stone of Bath. Be- 
neath these follow other beds of blue 
clay, with Fuller's earth, based upon 
another oolitic lime-stone, which is fol- 
lowed by slightly calcareous sands. 
Extent. — This fonnation commences also at the south-western extremity of 
Dorset, and runs north-east, swelling out, here and there, and in Gloucester, 
Oxford, and Northampton attaining a width of 15 to 20 miles. It occupies 
nearly the whole of these three counties, covers almost the entire area of Kut- 
land, a large portion ofthe north-east of Leicester, and then, in a narrow stripe, 
stretches north through Lincoln, and disappears at the Humber. It appears 
again in the North Riding of Yorkshire, skirting the outer edge of the middle 
oolite, on the north of w^hich it attains a breadth of 15 miles, and stretches 
across, with little interruption, from near Thirsk to the North sea. A small 
patch of it appears farther north, on the south-eastern coast of Sutherland, and 
on the east and south of the Isle of Sky. 

Soil. — It will be understood from what has been already stated in reference 
to other formations, that one which contains so many different rocks, as this 
does, must also present many diversities of soil. Where the upper beds come 
to the surface, the clay-partings give the character to the soil — forming a calca- 
reous clay, which, when dry or drained, is of good quality. In other places it 
forms a close adhesive clay, which is naturally almost sterile. The Bath oolite 
weathers and crumbles readily. The soil upon it is thin, loose, and diy. The 
rock is full of vertical fissures, which carry off the water and drain its surface. 



OLD PASTURES OF THE LIAS. 247 

When free from fragments of the rock, the soil is often close and imper\'iou3, 
and, though of a brown colour, deep, and apparently of good quality, it is really 
worthless, or, as the farmers call it, dead and sleepi/. Most of this land, how- 
ever, is in arable cultivation. The heavy soils, which rest on the clay contain- 
ing Fuller's earth, are chiefly in pasture. 

The inferior oolite varies much in its character, containing, in some places, 
much lime-stone, while in others, as in Yorkshire, it forms a thick mass of sand- 
stones and clays, with occasional thin beds of coal. In Gloucester, Oxford, 
Northampton, and Rvitland, these lower beds form a tract of land about 12 miles 
in width. The soil is generally soft, sandy, micaceous, of a brown colour, and 
of a good fertile quality. It is deep, contains many fragments of the subjacent 
rock, is porous, and easily worked. Where the sand-stones prevail, it is of in- 
ferior quality. In these counties it is principally enclosed, and in arable culture, 
the sides of the oolitic hills and the clayey portions being in pasture. In York- 
shire, much of the unproductive moor land of the North Riding rests upon this 
formation. Nearly all the arable land in the county of Sutherland rests on the 
narrow stripe of the lower oolite rocks which occurs on its south-east coast. 
The debris of these rocks has formed a loamy soil, which, when well limed, 
produces heavy crops of turnips. 

11°. Lias. 500 to 1000 ft. This great deposit consists chiefly of 

an accumulation of beds of blue clay, 
more or less indurated — interrupted m 
various places by beds of marl, and of 
blue, more or less earthy, lime-stones, 
which especially abound in the lower 
part of the series. The whole is full of 
shells, and of the remains of large ex- 
tinct animals. 
Extent. — Wherever the lower oolites are to be traced in England, the lias 
is seen coming up to the surface on its northern or western edge, pursuing an 
exceedingly tortuous north-eastern course, throwing out m its course many 
arms (outliers), and varying in breadth from 2 to 6 or 10 miles. It may be 
traced from the mouth of the Tees, in Yorkshire, to Lyme Regis, in Dorset, the 
continuity being broken only by the coal field of Somerset, In Scotland and 
Ireland no traces of this formation have yet been detected. 

Soil. — Throvxghout the whole of this formation the soil is a blue clay, more 
or less sandy, calcai-eous, and tenacious. Where the lime or sand prevails the 
soil is more open, and becomes a loam ; where they are less abundant, it is of- 
ten a cold, blue, unproductive, wet clay. This latter, indeed, may be given as 
the natural character of the entire formation. Where it rests upon a gravelly 
or open subsoil, or contains a large quantity of vegetable matter, it may be 
cultivated to advantage, and it is found especially to produce good herbage. In 
all situations, it is an expensive soil to work, and hence by far the gi'eater por- 
tion of it is in old pasture. The celebrated dairy districts of Somerset, Glou- 
cester, Warwick, and Leicester, rest for the most part on the lias, as does also 
much of the best grazing and pasture land in Nottingham and Yorkshire. 
Through the long lapse of time an artificial soil has been produced on the un- 
disturbed surface of these clay districts, which is peculiarly propitious to the 
growth of grass. With skilful drainage and judicious culture, it is capable of 
producing heavy crops of wheat. 

C. — New Red Sand-stone System, 
12°. Upper and Lower ) j.^^ /. The upper and lower red sand-stones 

Red Sand- stones. \ -' consist of alternate layers of sand, sand- 

stones, and marls sometimes colourless, 
but generally of a red colour — sprinkled 
in the upper series with frequent green 



248 FERTILE MARLS OF THE NEW RED SAN0-STONE. 

spots. The lower beds are sometimes 
full of rolled pebbles. Few of the sand- 
stones of this formation are sufficiently 
hard to form building stones — many of 
the layers consist of loose friable sand, 
and the marls universally decay and 
crumble to a fine red powder under the 
influence of the weather. 
Extent. — The new red sand-stone extends over a larger portion of the surface 
of England than any other formation. It commences at I'orbay, in the south 
of Devon, runs north-east into Somersetshire ; from Bristol ascends both sides 
of the Severn, accompanies it into the vale of Gloucester, stretches along the 
base of the Malvern hills, and north of the city of Worcester expands into a 

fently undulating plain, nearly 80 miles in width at its broadest part, compre- 
ending nearly the whole of the counties of Warwick and Stafford and the 
greater part of that of Leicester. From this central plain it parts into two di- 
visions. One of these runs west over the whole of Cheshire — (in which 
county it contains salt springs and mines of rock salt) — the western part of 
Flint, and on the south-west surrounds the county of Lancashire, It is there 
interrupted by the rising of the older rocks in Westmoreland, but re-appears in 
the eastern corner of this county, runs north-west through Cumberland, form- 
ing the plain of Carlisle — and thence round and across the Solway Frith till it 
finally disappears about 20 miles north of Dumfries. The other arm, proceed- 
ing from the towns of Derby and Nottingham, runs due north through Notting- 
ham and the centre of Yorkshii'e, skirting the outer edge of the lias, and finally 
disappears in the county of Durham to the north of the river Tees. The south- 
ern portion of this arm has a width of 20 to 30 miles, until it reaches the neigh- 
bourhood of Knaresborough, where it suddenly contracts to 6 or 8, and does 
not again expand to more than 10 or 12 miles. 

North of Dumfries-shire these rocks are not known to occur in our island. 
In the north-east of Ireland they form a stripe of land a few miles in width, run- 
ning from Lough Foyle to Lough Neagh, and thence, with slight interruptions, 
to the south of Belfast. 

Soil. — These rocks, by their decay, almost always produce a deep red 
soil. Where the red clay and marl predominate, this soil is a red clay or 
clayey loam of the richest quality, capable of producing almost every crop, and 
remarkable therefore for its fertility. It is chiefly in arable culture, because of 
the comparative ease with which it is worked, but the meadows are rich, and 
produce good herbage. Where the rocks are more sandy, and contain few 
marly bands, the soil produced is poorer, yet generally forms a good sandy loam, 
suitable for turnips and barley. 

In Devonshire, as in the vale of Taunton and other localities, where the lias 
and the red sand-stons adjoin each other, or run side by side, the diflference in 
the fertility and general productiveness of the two tracts is very striking. On 
the former, as already observed, good old grass land is seen, but the arable land 
on the latter produces the richest and most luxuriant crops to be seen on any 
soil in the kingdom. In this county, and in Somerset, the only manure it seems 
to require is lime, on every repetition of which it is said to produce increased 
crops. The same remarks as to its comparative fertility, apply with more or 
less force to the whole of the large area occupied by this formation in our island 
— wherever the soil has been chiefly formed by the decomposition of the rock 
on which it rests. In some localities (Dumfries-shire) the micaceovs, marly 
rock is dug up, and, after being crumbled by exposure to a winter's frost, is laid 
on with advantage as a top-dressing to grass and other lands. 

In the south of Lancashire, and along its western coast, and on the shores of 
the Solway, in Dumfries-shire, a great breadth of this formation is covered with 
peat. 



SOILS OF THE MAGNESIAN LiaiESTONE AND COAL MEASURES. 249 

13°. Magncsian Lime-stone^ The magnesian lime-stone is gene- 

rally of a yellow, sometimes of a grey, 
colour. In the upper part it occasion- 
ally pi-esents itself in thin beds, which 
crumble more readily when exposed to 
the air. In some places, also, it assumes 
a marly character, forming masses 
which are soft and friable ; in general, 
however, it is in thick beds, hard and 
compact enough to be used for a build- 
ing stone or for mending the roads. The 
quantity of carbonate of magnesia it 
contains varies from I to 45 per cent. 
It is in the north of England generally 
traversed by vertical fissures, which ren- 
der the surface diy, and make water in 
many places difficult to be attained. 
Extent. — The magncsian lime-stone stretches in an almost unbroken line 
nearly due north from the city of Nottingham to the mouth of the river Tyne. 
It is in general only a few miles in width, its principal expansion being in the 
county of Durham, where it attains a breadth of 8 or 10 miles. 

Soil. — It forms, for the most part, a hilly country, covered by a reddish 
brown soil, often thin, light and poor, where it rests immediately on the native 
rock — producing indifferent herbage when laid down to grass, but under skilful 
management capable of yielding average crops of turnips and barley. In the 
eastern part of the county of Durham tracts of the poorest land rest upon this 
rock, but as this formation is for the most part covered with deep accumulations 
of transported materials — the quality of the soil is in very many places more 
dependent upon the character of this superficial covering than upon the nature 
of the rock beneath. 

During the slow degradation of this rock, the rains gradually wash out great 
part of the magnesia it contains, so that it seldom happens that the soil formed 
from it, though resting on the parent rock, contains so mnch magnesia as to be 
necessarily hurtful to vegetation. 

D. — Carboniferous System. 

14°. Coal Measures. 300//!. Consisting of alternate beds of indu- 

rated bluish-black clay (coal shale), of 
sihceous sand-stone generally grey in 
colour and containing imbedded plants, 
and of coal of various qualities and de- 
grees of thickness. Beds of lime-stone 
rarely appear in this formation till we 
approach the lowest part of the series. 
Extent. — Fortunately for the mineral resources of Great Britain, the coal 
measures occupy a large area in our island. Most of the districts in which 
they occur are so well known as to require only to be indicated. The south 
Welsh coal-field occupies the south of Pembroke, nearly the whole of Glamor- 
gan, and part of Monmouth-shire. In the north of Somerset are the coal mea- 
sures of the Bristol field, which stretch also across the Severn into the forest of 
Dean. In the middle of the central plain of the new red sand-stone, lie the coal- 
fields of Ashby-de-la-Zouch, of Coventry, and Dudley, and on its western 
borders ai-e those of Shropshire, Denbigh, and Flint (North Wales). To the 
north of this plain extends on the right the Yorkshire coal-field from Notting- 
ham to Leeds, while on the left is the small coal-field of Newcastle-under-Line, 
and the broader Lancashire field which crosses the country from near Liverpool 
to Manchester. Almost the entire eastern half of the county of Durham, and 



250 MOOR-LANDS OF THE MILLSTONE GRIT. 

of the low country of Northumberland, is covered with these measures — but 
the largest area covered by these rocks is in that part of the low country of 
ticotland which extends in a north-easterly direction from the west coast of 
Ayrshire to the eastern coast of Fife. They there form a broad band, having 
an average breadth of 30 miles, interrupted often by trap or gi-een-stone rocks, 
yet lying immediately beneath the loose superficial matter, over the largest por- 
tion of this extensive district. They do not occur further north in our island. In 
Ireland they form a tract of limited extent on the northern borders of the county 
ofMonaghan — cover a much larger area in the south-east in Kilkenny and 
dueen's counties — and towards the mouth of the Shannon, spread on either 
bank over a large portion of the counties of Clare, Kerry, and Limerick. 

Soil. — The soil produced by the degradation of the sand-stones and shales 
of the coal formation is universally of inferior quality. The black shales or 
schists form alone a cold, stiff, ungrateful clay. The sand-stones alone form 
thin, unproductive soils, or barren — almost naked — heaths. When the clay 
and sand are mixed a looser soil is produced, which, by heavy liming, by drain- 
ing, and by skilful culture, may be rendered moderately productive. In the 
west of the counties of Durham and Northumberland, and on the higher edges 
of most of our coal fields, there are extensive tracts of this worthless sand-stone 
surface, and thousands of acres of the improveable cold clays of the shale beds. 
These latter soils appear very unpromising, and can only be rendered remune- 
ratively productive in skilful hands. They present one of those cases in which 
the active exertions of zealous agriculturists, and the efforts of the friends of 
agriculture, might be expended with the promise of much benefit to the country, 

15°. Millstone Grit. 600/1. This formation consists in some lo- 

calities of an entire mass of coarse sand- 
stone, of great thickness — in others of 
alternations of sand-stones and shales, 
resembling those of the coal-measures 
— while in others, again, lime-stones, 
more or less siliceous, are interposed 
among the sand stones and shales. 
Extent. — A large portion of Devonshire is covered with these rocks — they 
form also the high land which skirts to the north and west the coal-measures of . 
Yorkshire, Lancashire, and Durham, and over which is the first ascent to the 
chain of mountains that run northward through these three counties. In Scot- 
land, they have not been observed to lie immediately beneath any part of the sur- 
face. In the north of Ireland they cover a considerable area, stretching across 
the county of Leitrim between Sligo and Lough Erne. 

Son.. — The soils resting upon, and formed from, these rocks are generally of 
a very inferior description. Where the sand-stones come to the surface, miles 
of naked rock appear; other tracts bear only heath, or, where the rains have 
only a partial outlet, accumvtlations of peat. The shale-beds, like those of the 
coal-measures, afford a cold, unproductive, yet not unimproveable soil — it is 
only where lime-stones occur among them that patches of healthy verdure are 
seen, and fields which are readily susceptible of profitable arable culture. 

It is true, therefore, of this formation in general, that the high grounds form 
extensive tracts of moor-land. In the lower districts of country over which it , 
extends, the soil generally rests not on the rocks themselves, but on superficial | 
accumulations of transported materials, which are often of such a kind as to 
form a soil either productive in itself or capable of being rendered so by skilful 
cultivation. 

16°. Mountain ) q^« ^ In this formation, as its name implies, ■ 

Lime-stone. \ ^ lime-stone is the predominating rock. I 

It is generally hard, blue, and moi^ or 



SWEET PASTURES OF THE MOUNTAIN LIME-STONE. 251 

less full of organic remains. In some 
localities, it occurs in beds of vast thick- 
ness — (Derby and Yorkshire) — while 
in others — (Northumberland) — it is di- 
vided into numerous layers, with inter- 
posed sand-stones and beds of shale, and 
occasional thin seams of coal. 
Extent, — The greater portion of the counties of Derby and Northumberland 
are covered by this formation, and from the latter county it stretches along the 
west of Durham through Yorkshire as far as Preston, in Lancashire — forming 
the mountains of the well known Pennine chain, which throw out spurs to the 
east and west, and thus present on the map an iiTegular outline and varying 
breadth of country. In Scotland these rocks cover only a small portion of the 
county of Berwick, immediately on the Border; but in Ireland, almost the en- 
tire central part, forming upwards of one-half of the whole island, is occupied 
by the mountain lime -stone formation. 

Soil. — From the slowness with which this rock decays, many parts of it are 
quite naked ; in others, it is covered with a thin light porous soil of a brown 
colour, which naturally produces a short but thick and sweet herbage. Much 
of the mountain lime-stone country, therefore, is in natural pasture. 

Where the lime-stones are mixed or intersti'atified with shale beds, which de- 
cay more easily, a deeper soil is found, especially in the hollows and towards 
the bottom of the valleys. These are often stiff and naturally cold, but when 
well drained and limed produce excellent cx'ops of every kind. In Northumber- 
land, much of the mountain lime-stone country is still in moor-land, but the ex- 
cellence of border farming is gradually rescuing one improveable spot after ano- 
ther from the hitherto unproductive waste. In Yorkshire and Devonshire also 
improvements are more or less extensively in progress, though, in all these dis- 
tricts, there are large tracts which can never be re-claimed, 

E, — Old Red Sand-stone or Devonian System. 

17°. Old Red Sand' } 500 to The upper part of this formation con- 

stow^. ( 10,000 ft. sists of red sand-stones and conglomer- 

Old Red Conglomerate. ^^^s (indurated sandy gravel), the mid- 

Corn-stone and Marls. die of spotted, red and green, clayey 

Tile-stone. marls, with irregular layers of hard, of- 
ten impure and siliceous lime-stones 
(corn stones) likewise mottled, and the 
lowest of thin hard beds of siliceous 
sand-stones, sometimes calcareous, mot- 
tled, and splitting readTly into thin flags 
(tile-stones). 

Extent. — Though occasionally of vast thickness, the old red sand-stone does 
not occupy a very extensive area in our island. In the south of Pembroke it 
forms a tract of land on either side of the coal-field — surrounds on the north and 
east the coal-field of Glamorgan, and immediately north of this county covers a 
large area comprehending the greater portion of Brecknock and Hereford, and 
part of Monmouth. A small patch occurs in the Isle of Anglesey, and in the 
nox'th-eastern corner of Westmoreland — but it does not again present itself till 
we reach the western flank of the Cheviot Hills. It there appears on either 
side of the Tweed, and extends over a portion of Berwick and Roxburgh to the 
base of the Lammermuirs. On the north of the same hills it again presents it- 
self, and stretching to the south-west, forms a considerable tract of countiy in 
the counties of Haddington and Lanark. On the north of the great Scottish 
coal-field it forms a broad band, which runs completely across the island in a 
south-western direction along the foot of the Grampians, from Stonehaven to 



252 RICH WHEAT LANDS OF THE OLD RED SAND-STO>E. 

the Filth of Clyde, is to be discovered in the Island of Arran, and at the Mull 
of Cantire, and — along the prolongation of the same line — at various places on 
the northern flank of the great mountain lime-stone formation of Ireland, and 
especially in the counties of Tyrone, Fermanagh, and Monaghan. In the 
north of Scotland, it lines either shore of the Moray Firth, skirts the coast to- 
wards Caithness, where it covers nearly the whole county, and still further 
north, forms the entire surface of the Shetland Islands. Along the north-west- 
ern coast, it also appears in detached patches till we reach me southern ex- 
tremity of the Isle of Sky. 

In Ireland, it occurs also on the extreme southern edge of the mountain lime- 
stone, in Waterford and the neighbouring counties — and in the middle of this 
formation on the upper waters of the Shannon, in the south of Mayo, and 
round the base of the slate mountains ofTipperary. 

Soil. — The soil on the old red sand-stone admits of very nearly the same 
variations as on the new red sand-stone formation. Where it is formed, as in 
parts of Pembroke, from the upper sand-stones and conglomerates, it is either 
worthless or it produces a poor hungry soil, "which eats all the manure, and 
drinks all the water." These upper rocks are sometimes so siliceous as to be 
almost destitute both of lime and clay — in such cases, the soils they form are 
almost valueless. 

The marly beds and lime-stones of the second division, yield warm and rich 
soils — such as the mellow lands of Herefordshire, and the best in Brecknock 
and Pembroke shires. The soil in every district varies according as the partings 
of marl are more or less numerous. These easily crumble, and where they 
abound form a rich stiff wheat soil — like that of East Lothian and parts of Ber- 
wickshire ; — where they are less frequent the soil is lighter and produces excellent 
turnips and barley. Where the subsoil is porous, this land is peculiarly fa- 
vourable to the gi'owth of fruit trees.* The apple and the pear are largely grown 
in Hereford and the neighbouring counties, long celebrated for th6 cider and 
perry they produce. 

The tile-stones reach the surface only on the northern and western edges of 
this formation in England. In Ayrshire, in Lanarkshire, in Ross-shire, and in 
Caithness, larger tracts of land rest on these lower beds. In all these districts 
rich corn lands are produced from the rocks of the middle series. The fertility 
of Strathmore in Perthshire, and of other vallies upon this formation, is well 
known — Easter Ross and Murray have been called the granaiy of Scotland, 
and even in Caithness rich corn-bearing (oat) lands are not unfrequent. Yet 
in the immediate neighbourhood of these rich lands, tracts of tile-stone country 
occur, which are either covered with useless bog (Ayrshire and Lanarkshire), 
or with a thin covering of soil which is almost incapable of profitable culture. 
In this latter condition is the moor of Beauly on the Cromarthy Firth, an area 
of 50 square miles, which, till within a few years, lay as an unclaimed common 
— and in the county of Caithness still more extensive tracts. 

In South Devon and part of Cornwall a very fertile district rests also on the 
middle series of these rocks. Instead of red sand-stones, however, the country 
there consists of green slates, more or less siliceous, of sand-stones and of lime- 
stones, which by their decay have formed a very productive soil. These rocks 
in the above counties abound in fossil remains, and it is chiefly for this reason 
that the term Devonian has been applied to the rocks of the old red sand-stone 
formation. 

♦ The most loamy of these red soils of Hereford afford the finest crops of wheat and hops, 
and bear the most prolific apple and pear trees, whilst the whole region (eminently in the 
heavier clayey tracts) is renowned for the production of the sturdiest oaks, which so abound 
as to be styled the " weeds of Herefordshire." Thus, though this region contains no mines, 
the composition of its rocks is directly productive of its great agricultural wealth.— MwrcAi- 
*on, Silurian System, I., p. 193. 



MUDDY S OILS OF THE LOWER LUDLOW ROCKS. 253 

III. Primary Strata.— In these rocks slates abound, and lime- 
stones are more rare. Organic remains are also less frequently met 
with than m the superior rocks. These remains belong all to extinct 
species, the greater part to extinct genera and families, and are frequent- 
ly so wholly unlike to existing races that it is often difficult to trace any 
resemblance between the animals which now live and those which appear 
to have inhabited the waters of those ancient periods. 

F. — Silurian System. 

18°. Upper Silurian. 3800//-. The upper Ludlow rocks consist of 

1°. Ludlow formation. sand-stones more or less calcareous and 

a Upper Ludlow ) argillaceous. These rest upon hard, 

b Aymestry Lime-stone > 2000 somewhat crystalline, earthy lime- stones 

c Lower Ludlow ) (Aymestry lime-stones.) The lower 

20. Wenlock formation fc"^!'"'^ T^^ are masses of shale more 

a Lime-stone i , ^,, ll^ from lime and sand than the upper 

/, Shale ( 1®^^ ' ^"<i""om the mode in which they 

) decay into vmd are locally known by 

the name of " mud-stones." 

The Wenlock or Dudley formation 
consists in the upper part of a great 
thickness of lime-stone beds often argil- 
laceous, and abounding in the remains 
of marine animals ; and in the lower 
part of thick beds of a dull clayey shale 
— in its want of cohesion, and in its 
mode of decay, very much resembling 
_ the mud-stoTies of Ludlow. 

ILXTENT.— The principal seat of these rocks in our island is in the eastern 
counties of Wales, where they lie immediately beneath the surface over the 
eastern half of Radnor, and the north of Montgomery. 

Soil.— The prevailing character of the soils upon these formations is derived 
from the shales and mud-stones— and from the earthy layers of the sand-stones 
and hme-stones which decay more readily than the purer masses of these rocks. 
Ihe traveller IS immediately struck in passing- from the rich red marls and 
clays of the old red sand-stone in Hereford, on to the dark, almost black, soils 
ot the upper and lower Ludlow rocks in Radnor, not merely by the change of 
coJour, t)ut by their obviously diminished value and productiveness. The up- 
per Ludlow IS crossed by many vertical cracks and fissures, and thus, thouffh 
clayey, the soil which rests upon it is generally dry, and susceptible of cultiva- 

Not so the muddy soils of the lower Ludlow and Wenlock rocks. They are 
generally more or less impervious to water, and being subject to the drainage 
of the upper beds, form cold and comparatively unmanageable tracts. It is only 
where the intermediate lime-stones (Aymestry and Wenlock Hme-stones) come 
to the surface and mmgle their debris with those of the upper and lower rocks, 
that the stilt clays become capable of bearing excellent crops of wheat. This 
tact, however, indicates the method by which the whole of these cold wet clays 
might be greatly improved. By perfect artificial drainage and copious limeing. 
the unproductive soils of the lower Ludlow and of the Wenlock shales might be 
converted into wheat lands more or less rich and fertile. It unfortunately hap- 
pens, however, that in those districts of North and South Wales, where the 
dark grey or black " rotchy" land of the mud-stones prevails, lime is often so 
scarce, or has to be brought from so great a distance, as to render this means of 
improvement almost unattainable. 
22 



254 MOUNTAINOUS COUNTRY OF THE SLATE ROCKS- 

19° Lower Silurian. 3700 ft. The Caradoc beds consist of thick 

Caradoc Sand-stones 2500 ^^V^'^ °^ sand-stone of various colours, 

Llandeilo Flags 1200 '^^^^•"S "P""' ^"^ f-^'i'^^-i^iu^"!"!?- 

*-■* ^ casionally interstratified with, thin beds 

of impure lime-stone. The Llandeilo 
flags which lie beneath them consist of 
thin calcareous strata, in some locali- 
ties alternating with sand-stones and 
shales. 
Extent. — These rocks form patches of land in Shropshire and the north of 
Montgomery — and skirt the southern and eastern edge of Caemiarthen. None 
of the Silurian rocks have yet been found to extend over any large portion of 
either Scotland or Ireland. 

Soil. — The Caradoc sand-stone, when free from lime, produces only a 
naked surface or a barren heath. The Llandeilo flags form a fertile and arable 
soil, as may be seen in the south of Caermarthen, where they are best devel- 
oped, and especially on the banks of the Towey, which for many miles before 
it reaches the town of Caermarthen runs over this formation. 

In this formation, as in every other we have yet studied, the soil changes im- 
mediately on the appearance of a new rock at the surface. The soil of the 
Wenlock shale is sometimes more sandy as it approaches the Caradoc beds, 
and on favourable slopes forms good arable land and sustains luxuriant woods, .j 
but where the Caradoc sand-stones reach the surface, a wild heath or poorf] 
wood-land stretches over the country^ until passing over their edges we reach 
the lime-containing soils of the Llandeilo flags, when fertile arable lands and ^ 
lofty trees again appear.* 

G. — Cambrian System. 

20°. Ujjper Sr Lower Cam- ) These rocks, which are many thou- 1 

brian Rocks. S sand yards in thickness, consist chieflyl 

of thin slates, often hard and cleaving*] 
readily, like roofing slates, occasionally/j 
intermingled with sandy and thin lime- 
stone beds. They contain few organic 
remains. 
Extent. — These rocks cover the whole of Cornwall, part of North and 
South Devon, the western half of Wales, the entire centre of the Isle of Man, 
and a large part of Westmoreland and South Cumberland. In Scotland, they 
form a band between 30 and 40 miles in width, which crosses the island from 
the Mull of Galloway to St. Abbs Head. They form also a narrow stripe of 
land, which recrosses the island along the upper edge of the old red sand-stone 
from Stonehaven to the Isle of Bute, and, further north, spread over a consider- 
able portion of Banffshire. In the south-west of Ireland they attain a great 
breadth, are narrower at Waterford, but form a broad band along the granite 
mountains from that city to Dublin. They extend over a large portion of the 
counties of Louth, Cavan, Monaghan, Armagh, and Down, — form a narrow 
stripe also along the coast of Antrim as far north as the Giant's Causeway, — 
and, in the interior of Ireland, re-appear in the mountainous district of Tip- 
perary. 

Soil. — The predominance of slaty rocks in this formation imparts to the soils 
of the entire surface over which they extend one common clayey character. 
They generally form elevated tracts of country, as in Wales, Cumberland, 
Scotland, and Ireland, where the rigours of the climate combine with the fre- 
quent thinness and poverty of the soil to condemn extensive districts to woitU- 

* Such a passage from one formation to another is exhibited in the diagrams inserted in 
page 238. 



HEATHS AND BOGS ON THE GNEISS ROCKS. 255 

less heath or to widely extended bogs. Yet the slate rocks themselves, especi- 
ally when they happen to be calcareous, are capable of producing fertile soils. 
Such are found in the valleys, on the hill sides, and by the margins of the lakes 
that are often met with in the slate districts. More extensive stripes or bands 
of such productive land occur also at lower levels, as in the north of Devon, and 
in the south of Cornwall. In the latter county, the soils on the hornblende slate 
(which lies near the bottom of the slate series)are extremely fertile, exhibiting a 
striking contrast with those which are formed from the neighbouring Serpentine 
rocks, that extend over a large ai-ea immediately north of the Lizard (see p. 265.) 

Where the clay-slate soils occur, therefore, however cold and stiff they may 
be, a favourable climate, drainage, if necessary, and lime, either naturally pre- 
sent, or artificially added, appear to be the first requisites to insure fertility. 

The mode in which these rocks lie, or the degree of inclination which the 
beds exhibit, exercises an important influence upon the agricultural character 
of the soils that rest upon them. In the diagram inserted in page 238, the 
rocks (A) represent the highly inclined, often nearly vertical position, in which 
the slate rocks are most frequendy found. The soil formed from them must, 
therefore, rest on the thin edges of the beds. Thus it happens in many lo- 
calities that the rains carry down the soluble parts of the soil and of the manure 
within the partings of the slates— and hence the lands are hungiy and unprofit- 
able to work. 

On the slopes of the clay slate hills of the Cambrian and Silurian systems, 
flourish tlie vineyards of the middle Rhine, the Moselle, and the Ahr. 

H. — Mica-Slate and Gneiss Systems. 

21 °. Mica- Slate, Gneiss Rock. The upper of these formations con- 

sists of thin undulating layers of rock, 
consisting chiefly of quartz and mica, 
alternating occasionally with green 
(chlorite) slates, common clay-slates, 
quartz rock and hard crystalline lime- 
stones. The gneiss is a hard and 
solid rock of a similar nature, consist- 
ing of many thin layers distinctly vi- 
sible, but firmly cemented, and as it 
were half-melted together. 
Extent.— Two-thirds of Scotland, comprehending nearly the whole country 
norih and west of the Grampians, consist of these rocks. In England there 
is only a small patch of mica slate about Bolt Head and Start Point in South 
Devon, and a somewhat larger in Anglesey ; but in Ireland, nearly the whole 
of the counties of Donegal and Londonderry on the north, and a large portion 
of Mayo, Connaught, and Galway, on the west, are covered by rocks belonging 
to the mica slate system. 

Soils. — These rocks are, in general, harder still than those of the Cambrian 
system, and still more impervious to water, when not highly inclined. They 
crumble slowly, therefore, and imperfectly, and hence are covered with thin 
soils, on which, where good natural drainage exists, a coarse herbage springs, 
and from which an occasional crop of corn may be reaped — but on which, where 
the water becomes stagnant, extensive heaths and bogs prevail. That they 
contain, when perfectly decomposed and mellowed, the materials of a fertile soil, 
is shown by the richness of many little patches of land, that occur in the shel- 
tered valleys of the Highlands of Scotland, and by the margins of its many 
lakes. In general, however, the mica-slate and gneiss country is so elevated 
that not only does an ungenial climate assist its natural unproductiveness, but 
the frequent rains and rapid flowing rivers bear down to the bottoms of the val- 
lies or forward to the sea, much of the finer matter produced by the decay of the 
rocks, — leaving only a poor, thin, sandy soil behind. 



256 FERTILITY DEPENDENT ON GEOLOGICAL STRUCTURE. 

On these hard slate and gneiss rocks extensive pine forests in Sweden and 
Norway have long lived and died. In these countries it is customary in many 
places to burn down the wood, to strew the ashes over the thin soil, to harrow 
in the seed — to reap thus one or two harvests of rye, and to abandon it again to 
nature, A grove of beech first springs up, which is supplanted'by an after- 
growth of pine, and finally disappears. 



Such is a general description of the nature and order of succession of 
the stratified rocks, as they occur in Great Britain and Ireland — of the 
relative areas over which they severally appear at the surface — and of 
the kind of soils which they produce by their natural decay. The con- 
sideration of the facts above stated,* shows how very much the fertility 
of each district is dependent upon its geological structure — how much a 
previous knowledge of that structure is fitted to enlighten us in regard to 
the nature of the soils to be expected in any district — to explain anoma- 
lies also in regard to the unlike agricultural capabilities of soils ajipar- 
enily similar — to indicate to the purchaser where good or better lands 
are to be expected, and to the improver, whether the means of amelio- 
rating his soil by limeing, by marling, or by other judicious admixture, 
are likely to be within his reach, and in what direction they are to be 
sought for. There still remain some important branches of this subject 
to which, at the risk of fatiguing you, it will be my duty briefly to draw 
your attention in the following lecture. 

' For much of the practical information contained in this section, I have to express my 
obligations to the following works: — For the extreme southern counties, to De La Beche's 
Geological Report on Cornwall and Devon ; and to a paper by Sir Charles Lemon, Bart., on 
the Agricultural Produce of Cornwall ; — for Wales and the Border counties, to Murchison's 
Silurian System; — for the Midland counties of England, to Morton on Soils, a work I iiave 
in a previous note recommended to the attention of the reader; for Yorkshire, to a paper by 
Sir John Johnston, Bart., in the Journal of the Royal Agricultural Society ; — and for the Old 
Red Sand-stone of the north of Scotland, to the very interesting little work of Mr. Miller on 
The Old Red Sandstone. The reader would read the above section with much greater 
profit if he were previously to possess himself of Phillip's Outline Map of the Geology of the 
British Islands. 



LECTURE XIL 

Composition of the granitic rocks and of their constituent minerals— Cause and made of 
their degradation — Soils derived from them — Superficial accumulations — Their mfluence 
upon the character of the soils — Organic constituents, ultimate chemical constitution, and 
physical properties of soils. 

It has been stated in the preceding Lecture, (§ 6, p. 237), that the rocks 
which present themselves at the surface of the earth arc of two kinds, 
distinguished by the terms stratified and unstratified. The former 
crumble away, in general, more rapidly than the latter, and form a va- 
riety of soils of which the agricultural characters and capabilities liave 
been shortly explained. The unstratified or crystalline rocks form soils 
of so peculiar a character and possessing agricultural capabilities in 
general so different from those of the stratified rocks which occur in the 
same neighbourhood, and they, besides, cover so large and hitherto so 
unfruitful an area in our island, as to entitle them to a separate and 
somewhat detailed consideration. 

§ 1. Composition of the Granitic Hocks. 

The name of Granite is given by mineralogists to a rock consisting of 
a mixture more or less intimate of three simple minerals — Quartz, Mica, 
and Felspar. When Mica is wanting, and Hornblende occurs in its 
stead, the rock is distinguished by the name of Syenite. This mineral- 
ogical distinction is often neglected by the geologist, who describes large 
tracts of country as covered by granitic rocks, though there may be 
many hills or mountains of syenite. In a geological sense, the distinc- 
tion is often of little consequence; in relation to agriculture, however, 
the distinction between a granite and a syenite is of considerable im- 
portance. 

The minerals of which these rocks consist are mixed together in very 
variable proportions. Sometimes the quartz predominates, so as to con- 
stitute two-thirds or three-fourths of the whole rock, sometimes both 
mica and quartz are present in such small quantity as to form what is 
then called a felspar rock. The mica rarely exceeds one-sixth of the 
whole, while the hornblewde of the syenites sometimes forms nearly 
one half of the entire rock. These differences also are often overlooked 
by the geologist — though they necessarily produce important differences 
in the composition and agricultural characters of the soils derived from 
the crystalline rocks. 

A few other minerals occur occasionally among the granitic rocks, in 
sufficient quantity to affect the composition of the soils to which they 
give rise. Among these, the different varieties of tourmaline are in 
many places abundant. Thus the schorl rock of Cornwall consists of 
quartz and schorl (a variety of tourmaline), while crystals of schorl 
are so frequently found in the granites of Devon, Cornwallt and the 



258 COMPOSITION or granite, felspar, and albite. 

Scilly Isles, as to be considered characteristic of a very large portion of 
them (Dr. Boase). 

These rocks decay with very different degrees of rapidity — accord- 
ing to the proportions in which the several minerals are present in 
them, and to (he peculiar state of hardness or aggregation in which they 
happen to occur. Both the mode of their decay, however, and the cir- 
cumstances under which it takes place, as well as the character and 
composition of the soils formed from them, are materially dependent 
upon the composition of the several minerals of which the rocks consist. 
This composition, therefore, it will be necessary to exhibit. 

1°. Quartz has already been described (p. 206), as a variety of silica 
— the substance of flints, and of siliceous sands and sand-stones. In 
granite, it often occurs in the form of rock crystal, but it is more frequent- 
ly disseminated in small particles throughout the rocky mass. It is 
hard enough to scratch glass. 

2°. Felspar is generally colourless, but is not unfrequently reddish or 
flesh-coloured. On the colour of the felspar they contain, that of the 
granites most frequently depends. Several varieties of this mineral are 
known to collectors. Besides the common felspar, however, it is only 
necessary to specify Albite, which, in appearance, closely resembles fel- 
spar, often takes its place in granite rocks, and in chemical constitution 
differs from it only in containing soda, while the common felspar con- 
tains potash. These two minerals are readily distinguished from quartz 
by their inferior hardness. They do not scratch glass, and, in general, 
may easily be scratched by the point of a knife. 

They concist respectively of- 





Felspar. 


Albite. 


Silica . . 


. . 65-21 


69-09 


Alumina . 


. . 18-13 


19-22 


Potash . . 


. . 16-66 


._ 


Soda . . 


. . — 


11-69 



i 



100-00 100-00 

It is to be observed, however, that these minerals do not generally oc- 
cur in nature in a perfectly pure state — for though they do not essential- 
ly contain either lime, magnesia, or oxide of iron, they are seldom found 
without a sm*ll admixture of one or more of these substances. It is also 
found that while pure felspar contains only potash, and pure albite only 
soda, abundance of a kind of intermediate mineral occurs which contains 
both potash and soda. Such is the case with the felspar of the Siebenge- 
birge, on the right bank of the Rhine (Berthier), and with those con- 
tained in the lavas of Vesuvius and the adjacent parts of Italy (Abich). 

In these two minerals the silica is combined with the potash, soda, 
and alumina, forming certain compounds already described under the 
name oC silicates (p. 207). 

Felspar consists of a silicate of alumina combined with a silicate of 
potash. Albite of the same silicate of alumina combined with a silicate 
of soda. 

3°. Mica generally occurs disseminated through the granite in small 
shining scales or plates, which, when extracted from the rock, split readi- 
ly into numerous inconceivably thin layers. It sometimes occurs also 



COMPOSITION OF MICA AND HORNBLENDE. 259 

in large masses, and is of various colours — white, grey, brown, green, 
and black. It is soft and readily cut with a knife. The thin shining 
particles that occur in many sand- stones, and especially between the 
partings of the beds, and give them what is called a micaceous charac- 
ter, are only more or less weathered portions of this mineral. 

Mica also consists of silicates, though its constitution is not always so 
simple as that of felspar. In some varieties magnesia is present, whilst 
in others it is almost wholly wanting, as is shewn by the following com- 
position of two specimens from different localities. 



A 


Potash. 


Magnftsian. 




Mica. 


Mica. 


Silica 


46-10 


40-00 


Alumina . . . 


31-60 


12-67 


Prot-Oxide of Iron 


■' 8-65 


19.03 


Magnesia . . . 


— 


15-70 


Potash .... 


8-39 


5-61 


Oxide of Magnesia 


1-40 


0-63 


Fluoric Acid . . 


1-12 


2-10 


Water .... 


1-00 


Titanic Acid 1-63 



98-26 97-37 

If we neglect the three last substances, which are present only in small 
quantities, and recollect that the silica is in combination with all the 
oilier substances which stand beneath it, we see that these varieties of 
mica consist of a silicate of alumina, combined in the one with silicate 
of iron and silicate of potash^ and in the other with silicate of iron and 
silicate of magnesia. 

4°. Hornblende occurs of various colours, but that which forms a con- 
stituent of the syenites and of the basalts is of a dark green or brownish 
black colour, is often in regular crystals, and is readily distinguished 
from quartz and falspar by its cojpur, and from black mica by not split- 
ling into thin layers, when heated in the flame of a candle. It consists 
of silicates of aliimiaa, lime, magnesia, and oxide of iron, or percent, 
of— 

Basaltic Syenitic 

Hornblende. Hornblende. 

Silica 42-24 45-69 

Alumina .... 13-92 12-18 

Lime ..... 12-24 13-83 

Magnesia .... 13-74 18-79 

Prot-Oxide of Iron . 14-59 7-32 

Oxide of Manganese 0-33 0-22 

Fluoric Acid ... — 1-50 

97-06 99-53 

A comparison of these two analyses shows that the proportions of 
magnesia and oxide of iron sometimes vary considerably, yet that the 
hornblendes still maintain the same general composition. They are re- 
markably distinguished from felspar by the total absence of potash and 
soda, and by containing a large proportion of lime and magnesia. From 
the potash-mica they are distinguished by the same chemical differen- 
ces, and from the magnesian mica by containing lime to the amount of 



260 coMPOsiTio:^ of scuorl. 

|th part of their whole weight. 3uch differences must materially af- 
fect the constitution and agricultural capabilities of the soils formed from 
these several minerals, and they show the correctness of what I have 
previously stated to you — that mineralogical differences in rocks which 
may be neglected by the geologist, may be of great importance in ex- 
plaining the appearances that present themselves to the philosophical 
agriculturist. 

4°. Schorl usually occurs in the form of long black needles or prisms 
disseminated through the granitic rock, and generally (in Cornwall) at 
the outskirts of the granite, where it comes into contact with the slate 
rocks that surround it (De la Beche). It consists of a silicate of alumi- 
na in combination with silicates of iron and of soda or magnesia. Two 

varieties gave by analysis — 

Schorl TDurmaline 

from Devonshire. from Sweden. 

Silica, 35-20 37-65 

Alumina, .... 35-50 - 33-46 

Magnetic Oxide of Iron, 17-86 9-38 

Magnesia, .... 0-70 10-98 

Boracic Acid, . . . 4-11 3-83 

Soda, 2-09 Soda & potash, 2-53 

Lime, 0-55 0-25 

Oxide of Manganese, 0-43 — 

96-44 98-08 

This mineral, according to these analyses, is characterised by con- 
taining from ^ to ^ of its weight of magnetic oxide of iron,* and some- 
times yV of magnesia. The presence of Boracic acidf is also a remark- 
able character of this mineral, but as neither the presence of this sub- 
stance in any soil, nor its effect upon vegetation, have hitherto been ob- 
served, we can form no opinion in regard to its importance in an agri- 
cultural point of view. 

§ 2. O/* the degradation of the Granitic rocks, and of the soils formed 

from them. 

The granites, in general, are hard and durable rocks, and but little af- 
fected by the weather. The quartz they contain is scarcely acted upon at 
all by atmospheric agents, and in very many cases the felspar, mica, 
and hornblende yield with extreme slowness to their degrading power. It 
is chiefly to the chemical decomposition of the felspar that the wearing 
away of granite rocks is due, and the formation of a soil from their crum- 
bling substance. 

It has been stated that the felspars consist of a silicate of alumina in 
combination with silicates of potash or of soda. New these latter sili- 
cates are slowly decomposed by the carbonic acid of the air (see p. 207), 
which combines with the potash and soda, and forms carbonates of these 
alkalies. These carbonates are very soluble in water, and are, there- 

• This oxide is composed of the Jirst and second oxides of iron described in p. 210. 

t Boracic acid occurs in combination with soda in the common borax of the shops. It 
combines with soda, potash, Hme, &c., and forms borates. In the schorl it probably exists 
in such a state of combination. 



I 



CLAY FROM TIIR FELSPAR ROCKS. 261 

fore, washed away by the first shower of rain that falls. The insoluble 
silica and the silicate of ahimina are either left behind or are more slow- 
ly carried away by the rains in the form of a fine powder (a fine porce- 
lain clay), and deposited in the valleys or borne into the rivers and lakes, 
— while the particles of quartz and mica, having lost their cement of fel- 
spar, fall asunder, and form a more or less siliceous sand. 

Granite soils, therefore, on hH hanging grounds, — on the sides and 
slopes of hills, that is — are poor and sandy, rarely containing a suflScient 
admixture of clay to enable them to support crops of corn — while at the 
bottoms of the hills, whether on fiat or hollow grounds, tliey are com- 
posed, in great measure, of the fine clay which has resulted from the 
gradual decomposition of the felspar. 

This clay consists chiefly of the silicate of alumina contained natural- 
ly in the felspar — it differs little, in short from that which has already 
been described (p. 161), under the name of pure or pipe clay, which is 
too stiflfand intractable to be readily converted into a prolific soil. 

It will readily be understood how such soils — decomposed felspar soils' 
— must generally contain a considerable quantity of potash from the 
presence of minute particles of silicate of potash still undecomposed ; 
and it will be as readily seen that they can contain little or no lime, 
since neither in felspar nor in mica has more than a trace of this earth 
been hitherto met with. 

We have seen, however, that hornblende contains from ^th to |thof its 
weight of lime, and as the same carbonic acid of the atmosphere which 
decomposes the felspar, decomposes the silicates of the hornblende also, 
it is clear that soils which are derived from the degradation of syenitic 
rocks, especially if the proportion of hornblende present in them be large, 
will contain lime as well as clay and silica. Thus consisting of a great- 
er number of the elements of a fertile soil, they will be more easily 
rendered fruitful also — must naturally be more fruitful — than those 
which are formed from the granites, correctly so called. It is to the pre- 
sence of this lime that the superior fertility of the soils derived from the 
hornblende slates of Cornwall, already adverted to (p. 255), is mainly 
to be ascribed. 

Schorl, as above stated, contains much oxide of iron, and sometimes 
five or six per cent, of magnesia. It decomposes slowly, will give the 
soil a red colour, and though it contain only a trace of lime, yet the ad- 
mixture of its constituents with those of the felspar may possibly amelio- 
rate the quality of a soil formed from the decay of the felspar alone. 

It thus appears that a knowledge of the constitution of the minerals of 
which the granites are composed, and of the proportions in which these 
minerals are mixed together in any locality, clearly indicates v^hat the 
nature of the soils formed from them 7nust be — an indication which per- 
fectly accords with observation. The same knowle/3ge, also, showing 
that such soils never have contained, and never can, naturally, include 
more than a trace of Hrae, will satisfy the improver, who believes the 
presence of lime to be almost necessary in a fertile soil, as to the first 
step to be taken in endeavouring to rescue a granitic soil from a state of 
nature — will explain to him the reason why the use of lime and of shell 
sand on such soils, should so long have been practised with the best ef 



262 GRANITE KOCKS OF CRtAT BRITAiri AM) IRIJLA.XD. 

fects, — and will encourage him to persevere in a course of treatment 
which, while suggested by theory, is confirmed also by practice. 

Extent of granitic rocks in Great Britain and Ireland. — In England, 
the only extensive tracts of granite occur in Cornwall and Devon, pre- 
senting themselves here and there in isolated patches from the Scilly 
Isles and the Land's End to Dartmoor in South Devon. In the latter 
locality, the granite rocks cover an area of about 400 square miles. Pro- 
ceeding northward, various small out-hursts* of granite appear in the 
Isle of Anglesey, in Westmoreland, and in Cumberland, and north of 
the Solway, in Kirkcudbright, it extends over 150 or 200 square miles; 
— but it is at the Grampian Hills that these rocks begin to be most ex- 
tensively developed. With the exception, indeed, of the patches of old 
red sandstone already noticed, nearly the whole of Scotland, north of the 
Grampians — and of the western islands, excluding Skye and Mull, con- 
sists of granitic rocks. 

In Ireland, a range of granite (the Wicklow) mountains runs south by 
uest from Dublin to near New Ross — the same rock forms a consider- 
able portionof the mountainous districts in the north-west of Donegal, and 
iu the south of Galway — covers a less extensive area in Armagh, and pre- 
sents itself in the form of an isolated patch in the county of Cavan. 

Soils of the granitic rocks. — From what has been already stated in re- 
gard to the composition of granite, it is clear from theory that no gene- 
rally uniform quality of soil can be expected to result from its decom|x>- 
sition, and this deduction is confirmed by practical observation. Where 
(|uartz is more abundant, or where the clay is washed out, the soil is 
poor, hungry, and unfruitful — such, generally, is its character on the 
more exposed slopes of the bills in the Western Isles, and in the north 
of Scotland. — [Macdonald's Agricultural Survey of the Hebrides, p. 26.] 
In the hollows and levels, where natural drainage exists, stiff clay soils 
prevail, which are often cold and unfruitful, but are capable of amelio- 
ration where the depth of earth is sufficient, by draining and abundant 
liming or marling. Where there is no natural drainage, vegetable mat- 
ter accumulates, as we have seen to be the case on the surface of all im- 
pervious rocks — and bogs are formed. In the north of Scotland, and in 
Ireland, and in the high lands of Dartmoor (Devon), these are every- 
where seen in such localities, and it is said that two-thirds of the He- 
brides are covered with peat bogs more or less reclaimable. 

In Cornwall and Devon, the granitic soils {groivan soils, as they are 
there called) are observed to be more productive as the hills diminish 
in height. Thus Dartmoor is covered only with heath, coarse grass, 
and peat ; while in the Scilly Isles the growan land produces good crops 
of wheat, potatoes, barley, and grass ; and the same is observed al 
Morefon Hampstead, in Devon, where tolerable crops of barley are grown, 
and potatoes, which are highly esteemed in the Exeter market (De La 
Beche). No doubt the climate has something to do with these differ- 
ences ; but the less the elevation, and the consequent washing of the 
rains, the more of the clay will remain mixed with the siliceous sand ; 

* This expression is in some measure theoretical, and implies — what is the generally rr. 
ceived opinion— that the granite rocks were forced up from beneath in a fluid state, like the 
lavas of existing volcanoes— that they, as well as the trap rocks, are, in short, only lavas of 
a more ancient date (see p. 237). 



THE TRAP-ROCKS GREE^■-STO^E. 263 

while in aid of both these causes, a small difference in the composition 
of its constituent minerals, often not to be detected by the eye, may ma- 
terially affect the character of the granitic soils. 

According to Dr. Paris, the presence of much mica deteriorates these 
soils; while that which is formed at the edges of the granite, when it 
comes in contact with the slate rocks, is of a more fertile quality. The 
latter remark, however, does not universally apply, — especially where 
the granite, as at the edges of Dartmoor, contains much schorl, (De La 
Beche) — and the presence of mica, in the richest soils of the red marl, 
would seem to imply that this mineral is fitted materially to promote 
the fertility of a soil in which the other earthy ingredients are properly 
adjusted. 

The more elevated and thin granitic soils are said to be fitted for the 
growth of larch ; the lower and deeper soils, which admit of the use of 
the plough, have been found to yield a three-fold return of corn by the 
use of lime alone. 

§ 4. Of the trap rocks, and the soils formed from them. 

Of the trap rocks there are several varieties, of which the most impor- 
tant are distinguished by the names of Greenstone, Basalt, and Ser- 
11 en tine. 

The Greenstones consist of a mixture more or less intimate of felspar 
and hornblende, or of felspar and augite. They are distinguished from 
the granites by the absence of mica and quartz, and by the presence of 
the hornblende or augite, often in equal, and not unfrequently in greater 
quantity than the felspar. In the granites, the felspar and quartz lo- 
getl)er generally form upwards of -j^ of the whole mass. 

Augite is a mineral having much resemblance to hornblende, and, 
like it, occurring of various colours. In the trap rocks it is usually of a 
dark green approaching to black. It generally contains much lime and 
oxide of iron in the state of silicates. The composition of two varieties 
compared with that of basaltic hornblende is as follows : — 

Black Augite Augite from the Basaltic 

from Sweden. lava of Vesuvius. Hornblende. 

Silica 53-36 50-90 42-24 

Lime 22-19 22-96 12-24 

Magnesia 4-99 14-43 13-74 

Prot-Oxide of Iron . . . 17-38 6-25 14-59 

Prot-Oxide of Manganese . 0-09 — 033 

Alumina — 5-37 13-92 



98-01 99-91 97-06 

The predominance of this mineral (augite) or of hornblende in the 
green-stone rocks must necessarily cause a very material difference in 
the nature of the soils produced from their decay, compared with those 
which are formed from the granitic rocks in which the felspars are the 
predominating mineral ingredient. 

2°. Basalt consists of a mixture, in variable proportions, of augite, 
magnetic oxide of iron, and zeolite.* It differs in appearance from green- 

* '^'■With or without felspar V In addition to augite, magnetic iron, and zeolite, many ba- 
salts contain also a considerable portion of certain varieties of felspar, especially of one to 
which the name oinepheline has been given. 



264 EXTENT AND SOIL OF THE TRAP-KOCK3. 

Stone, chiefly by the darkness of its colour, and by the minuteness of the 
particles of which it is composed, which, in general, cannot be distin- 
guished by the naked eye. 

Zeolite is a generic term applied to a great number of mineral species 
which occur in the basalts, and often intermixed with the green-stone 
rocks. They differ from felspar in their greater solubility in acids, and 
by generally containing lime, where the latter contains potash or soda. 

it may be stated, indeed, as the most important agricultural distinc- 
tion, between the granitic and the true* trap-rocks, that the latter abound 
in lime, while in the former, it is often entirely absent. If in a green- 
stone only one-fourth of its weight consist of augite, every 20 tons of the 
rock may contain one ton of lime. If in a basalt the augite and zeolite 
amount to only two-thirds of its weight, every nine tons may contain a 
ton of lime. The practical farmer cannot fail to conclude that a soil 
formed from such rocks must possess very different agricultural capabil- 
ities from the soils we have already described as being formed from the 
decomposition of the granites. 

3°. Serpentine is a greenish yellow mineral, consisting of silica in 
combination with magnesia and a little iron, and occasionally a few 
pounds in the hundred of lime or alumina. The distinguishing ingredi- 
ent is the magnesia, which generally approaches to 40 ])er cent, of the 
whole weight of the mineral. Rocks of serpentine are generally mixed 
with magnetic iron ore, and with portions of other minerals in greater 
or less abundance. 

Extent of the trap rocks in the British Isles. — The serpentine rock oc- 
curs to any extent only in Cornwall, about the Lizard Point, where it 
covers an area of 50 square miles. The green-stones and basalts are 
only met with here and there in small patches, until we get so far north 
as the Cheviot Hills, which consist of these and other varieties of trap. 
It is in the low country of Scotland, however, intermixed with and sur- 
rounding the great coal district of that part of the island, that the greatest 
breadth of trap is seen. It there stretches across the island in a south- 
west direction, and in detached masses, from the Friths of Tay and 
Forth to the island of Arran, covering an area of 800 or 1000 square 
miles. In the prolongation of the same line it re-appears in the north- 
east of Ireland, and extends over the whole of the county of Antrim and 
a small part of Londonderry and Armagh. In the most northerly portion 
of this tract the well-known columnar basalt of the Giants' Causeway 
occurs. On the west coast of Scotland the trap rocks cover nearly the 
whole of the islands of Mull and of Skye — to the west of the former of 
which islands lies Staffa with its celebrated basaltic caves. 

Soil of the trap rocks. — The soil of the serpentine rocks at the Lizard 
is far from fertile, retaining the water and thus forming swamps and 
marshes. Even where a natural drainage exists it rarely produces good 
grass, or average crops of corn. It is remarkable for growing a pecu- 
liar, very beautiful heath — erica vagans — which so strictly limits itself 
to the serpentine soil as distinctly to mark the boundary by which the 
serpentine is separated from other rocks (De La Beche). From the 

" /yerpcnfiTie is not generally included among the true trap rocks: it is included amon? 
them here as it often is by geologists, because in Etiany places, aa at the Lizard, it occurs 
along with true green-stone. 



# 



FERTILITY OF THE GREEN-STOI«E SOILS. 265 

composition of serpentine we might be led to suppose that the compara- 
tive barrenness of the soils formed from it is due to the large quantiiy 
of magnesia which this mineral contains ; and this may, in some cases, 
be partly the cause. It would appear, however, that these soils often 
contain very little magnesia, the long action of the rains and of other 
agents having almost entirely removed it (see p. 209), and yet they stiil 
retain their barrenness. But they contain no lime, and, therefore, after 
draining, the first great step to take in order to improve such soils, is to 
give them a good dose of lime. How this step is to be followed up will 
depend upon the effect which this treatment is found to produce. 

The soil of the green-stones is generally fertile, and it is more so in 
proportion as the hornblende or augite predominates — that is, generally, 
in proportion to the darkness of its colour. 

In Cornwall and South Devon, where scattered masses of trap occur, 
consisting chiefly of hornblende and felspar, they "afford the most fertile 
soils of any in the district when their decomposition has taken place to 
a sufficient depth" (De La Beche). Wherever the trap rocks (locally 
dun-sLones) are observed at the surface, " it is deemed a fortunate cir- 
cumstance, being a certain indication of the fertility of the incumbent 
soils." — [Worgan's Vieiv of the Agriculture of Cornwall, p. 10.] The 
t^uperior fertility of the neighbourhood of Penzance is owing to the pre- 
sence of these rocks (Dr. Paris), and where their detritus has been mix- 
ed with that of other rocks — as with the worthless granite soils — it ame- 
liorates and improves their quality. 

The same general character is exhibited by the trappean soils of other 
districts of the island. The height of the Cheviot Hills renders the cli- 
mate in many places unfavourable to arable culture, yet they produce 
the sweetest pasture,* while the low country around them has been 
largely benefitted by admixture with their crumbling fragments. The 
whole of that lowland tract of Scotland, over which these rocks extend — 
comprehending the counties of Ayr, Renfrew, Lanark, Linlithgow, 
Fife, and portions of Perth, Sterling, Edinburgh, and Haddington, — ex- 
hibit the fertile or fertilizing character of the decomposing green-stone. 
In Cornwall it is dug up as a marl and applied to the land, and in the 
neighbourhood of Haddington I have seen a farming tenant {a leasehold- 
er) removing twelve inches of trap soil from the entire surface of a field, 
for the purpose of spreading a layer of an inch in depth over twelve 
times the area in another part of his farm. There can be no doubt that 
this mode of improvement is within the reach of many proprietors and 
farmers — especially along the southern borders of Perthshire, and near 
the more elevated of Ayr and Lanark. 

To the north of Ireland, and to the Western Islands, the above re- 
marks, with slight modifications, arising from local causes, will also ap- 
ply. For example, where the surface is flat, and the rock impervious, 
water will collect and heaths and bogs will be produced, which only 

* It is a singular fact observed here and there among the Cheviot Hills on the border, that 
where sheep are folded or pastured on tiills of trap which are covered with delicate herbage, 
ttiey are attacked by what is locally called \.\\e pining ill ^ — they pine away, become indolent, 
and are unwilling to move. The cure is to drive them to a nc'ignhounng sand sto7ie pasture, 
where they becorrie again active, and begin to thrive. The pining hills on each farm arc 
well known, and the tenant has no hesitation in pointing to this and to that hill as those on 
Which the sheep are sure to pine, if kept upon them only. 



266 THE HYPKRTHENE SOILS OF SKYE. 

draining can remove. They apply also to other countries where trap 
rocks abound — the only fertile tracts of Abyssinia, for ins:ance, being 
found in valHes and on mountain slopes, where the soil is composed of 
the detritus of trappean rocks (Dr. Rlippell , 

Yet there are exceptions to this general rule. 

Where the felspar is largely predominant, the soil formed from the 
rock will partake more or less of the cold and barren character of the 
stiffer granitic soils. Such appears to be the rase with some of the traps 
which occur in the border counties of England and Wales (Murchison). 

In the Isle of Skye, again, a local peculiarity of a different kind ob- 
tains, the effect of^which upon the soil is also to render it poor and un- 
productive. In that island the singularly beautiful ridge of the Cuchul- 
len Hills consists of a variety of trap in which the augite so far predomi- 
nates as to form nearly tlie whole of the mountain masses, But the 
augite in this case is a variety to which the name of hypersthene has 
been given, and which contains much magnesia and oxide of iron, but 
scarcely a trace of either lime or alumina. The rock is very hard, and 
decays with extreme slowness; yet however rapid its decay might be, 
it could never produce a fertile soil. We have seen that the serpentine 
and granite soils are essentially deficient in lime, but a hypersthene soil 
is in want both of lime and of clay. It would be still more difficult, 
therefore, to render the latter productive — even supposing, as in the case 
of the serpentine soils, that the magnesia of the hypersthene* were most- 
ly washed away by the rains. 

Thus we perceive how eactly the study of the composition of the dif- 
ferent varieties of the trap rocks explains the observed diflTerences in the 
quality of the soils derived from them. When the minerals they contain 
abound in lime, the soils they yield are fertile — when those minerals 
predominate in which lime is wanting, the soils are inferior, sometimes 
scarcely capable of cultivation. Again, the granites abound in potash; 
but except in the syenites they rarely contain lime, and their soils are 
generally poor. Let them be mixed with the trap soils, and they are 
enriched. This would seem fairly and clearly to imply that the fertility 
of the one is mainly due to the presence of lime, and the barrenness of 
the other to the absence of this earth. 

On this subject I will only further add, that the more modern volcanic 
lavas which overspread Italy, Sicily, parts of France, Spain, and Ger- 
many, are closely related to the trap rocks in their general composition 
— and the fertility which overspreads thousands of square miles of de- 
composed lava streams and ejections of volcanic ashes in Italy and Si- 
cily, is too well known to require any detailed description. 

§ 5. Of superficial accumulations of foreign materials, and of the means 
by which they have been transported. 

Abundant proof, I think, has now been advanced that a close relation 

* The hypersthene of Skye has been found to consist of— 

Silica 51-35 1 Prot-oxide of iron 3392 

Lime 1 84 | Water 0-50 

Magnesia 1109 I 

I 9870 
The composition probably varies in different parts of the rock, some containing more mag- 
nesia and less iron than is here representud. 



TRANSPORTED MATERIALS OFTEN MASK THE ROCKS. 267 

generally exists between the soil and the rocks on which it rests, and 
that the geological structure of a country, as well as the chemical consti- 
tution of the minerals of which its several rocky masses consist, have a 
primary and fundamental influence upon the agricultural capabilities of 
its surface. 

And yet I should be leading you into a serious error, were I to permit 
you to suppose that this intimate and direct relation is always to be ob- 
served — that in whatever district you may happen to be, you will find 
the soil taking its general character from the subjacent rocks — and that 
where the same rocks occur, similar soils are always to be expected. 
On the contrary, in very many localities the soil is totally different from 
that which would be produced by the degradation or decomposition of 
the rocks on which it rests. To infer, therefore, or to predict, that on a 
given spot, where, according to the geological map, red sand-stone for 
example prevails, a marly or other red sand-stone soil will necessarily 
be found — or that where the coal measures are observed, poor, ungrate- 
ful land must exist — would be to form or to state opinions which a visit 
to the several localities would ii] many instances show to be completely 
erroneous — and which would bring undeserved discredit upon geologi- 
cal science. 

In such cases as these geology is not at fault. New conditions only 
have supervened which render the natural relation between soils and 
rocks in those places less simple, and consequently more obscure. Yet 
a further study of geological phenomena removes the obscurity — shows 
to what cause it is owing that in many districts the soil is such as could 
never have been formed from the subjacent rocks — again places the en- 
lightened agriculturist in a condition to pronounce generally from what 
rocks his soils have been derived — generally also what their agricultural 
capabilities are likely to be, and by what mode of treatment those capa- 
bilities may be most fully developed. 

Of the surface of Great Britain and Ireland it may indeed be truly 
said, that it exhibits extensive tracts in which the character of the soil is 
directly influenced by, and may be inferred from, the character and 
composition of the subjacent rock. To these districts the rules and ob- 
servations contained in the preceding sections directly and clearly apply. 
But other extensive tracts also occur in which the character of the soil is 
independent of that of the rocks on which it immediately rests — the 
cause of this apparent difficulty we are now to consider. 

1°. I have already had occasion to explain to you in what way all 
rocks crumble more or less rapidly, and give origin to soils of various 
kinds. Were the surfaces of rocks uniformly level, and that of every 
country flat, the crumbled materials would generally remain on the spots 
where they were formed. But as already shown in the diagrams, in- 
serted in page 238, the rocks rarely lie in a horizontal position, 
but rest almost always more or less on their edges; and the surface in 
such a country as ours is often mountainous or hilly, and everywhere 
undulating. Hence the rains are continually washing off" the finer par- 
ticles from the higher, and bearing them to the lower grounds — and on 
occasions of great floods, vast quantities even of heavy materials are 
borne to great distances, and spread sometimes to a great depth and over 
a great extent of country — [witness the still recent floods in Morayshire.] 



268 EFFECT OF RAINS, RIVERS, AND TIDES. 

Thus the spoils of one rocky formation are borne from their native soil, 
and are strewed over the surface of other kinds of rock of a totally dif- 
ferent character. The fragments of the granite, gneiss, and slate rocks 
of the high lands are scattered over the old red sand-stones which lie at 
a lower level — and those of the blue lime-stone mountains over the mill- 
stone grits, the coal measures, and the new red sand-stones, which stretch 
away from their feet. 

2°. But the effects produced by this natural cause, though they may 
be judged of in kind, can never be estimated in degree by wliat we per- 
ceive in our own temperate climates — in our country of small rivers and 
gentle rains. How must such effects exceed in magnitude, in districts 
where, — as in the Ghauts, that separate the level land of the Malabar 
coast (the Concan) from the high table-land of the Deccan, — 120 inches 
of rain occasionally fall in a single month, and 240 inches or 20 feet, on 
an average, every year from June to September! And to what vast 
distances must materials be transported by great rivers, such as the Mis- 
sissippi, the River of Amazons, the Ganges, and the Indus, which main- 
tain a course of thousands of miles, before they empty themselves into 
the sea? What necessary connection can the deposits of mud and sand 
which yearly collect at the mouths and in the places overflowed by the 
waters of these great rivers, have with the nature of the rocks on which 
these transported materials may happen to rest? 

3°. But the constant motion of the waters of the sea washes down 
the cliffs on one coast, and carries away their ruins to be deposited, either 
in its own depths, or along other more sheltered shores. Hence sand 
banks accumulate — ^as in the centre of our own North Sea: or the land 
gains upon the water in one spot what it loses in another — as may be 
seen both on the shores of our own island, and on the opposite coasts of 
Germany and France. 

What necessary relation can the soils thus gained from the sea have 
to the rocks on which they rest? Suppose the bottom of the North Sea 
to become dry land, what necessary mineral relation would then exist 
between the soils which would gradually be formed on its hundreds of 
square miles of sand-banks, and the rocks on which those sand-banks 
immediately repose? 

4°. Again, the sea, in general, carries with it and deposits in its own 
bosom the finest particles of clay, lime, and other earthy matters, and 
leaves along its shores accumulations of fine siliceous sand. This sand, 
when dry, the sea winds bear before them and strew over the land, fonn- 
ing sand hills and downs, sometimes of considerable height and of great 
extent. Such are to be seen here and there, in our own islands, but on 
the Eastern shores of the Bay of Biscay, and on the coasts of Jutland, — 
both exposed to violent sea winds, — they occur over much larger areas. 
Before these winds the light sands are continually drifting, and, year by 
year, advance further and further into the country, gradually driving 
lakes before them, swallowing up forests and cultivated fields, with tlie 
houses of the cultivators, and burying alike the fertile soils and the rocks 
from which they were originally derived. [In the Landes, the ad- 
vance of the downs is estimated at 66 to 70 feet every year.] 

You have all read of the fearful sands of the African deserts, and of 



EFFECTS OF >YINDS, AND OF GLACIERS. 260 

their destructive march when the burning winds awaken. Elistory tells 
of populous cities and fertile plains, where nothing but blown sands are 
now to be seen, and geology easily leads us back to still more remote 
periods, when the broad zones of sandy desert were but narrow stripes 
of blown sand along the shores of the sea, or beds of comparatively loose 
sand-stone, which here and there came to the surface, and which the 
winds have gradually removed from their original site, and wafted widely 
over the land. 

Wherever these sand-drifts spread, it will also be clear to you, that 
there may be no necessary similarity between the loose materials on 
the surface and the kind of rock over which these materials are strewed. 

5°. Along with these I shall mention only one other great agent by 
which loose materials are gradually transported to considerable dis- 
tances. 

It is observed in elevated countries, where the snow never entirely 
melts, and where glaciers or sheets of ice hang on the mountain sides,-— 
descending towards the plains as the winter's cold comes on, and again 
retreating towards the mountairi-tops at the approach of the summer's 
heat — that the edges of the glaciers bear before them into the valleys, and 
deposit along their edges, banks of conical ridges of sand and gravel 
(^loraines)." These consist of the fragments of the rocky heights, worn 
and rounded by the friction of the sheets of ice beneath which they 
have descended from above, and from the edges of which they finally 
escape into the plain. 

These ridges of sand and gravel accumulate till some more sudden 
thaw than usual, or greater summer's heat arrives, when they are more 
or less completely broken up by the rush of water that ensues, and are 
dispersed over the subjacent tracts of level land. 

When the rocks are of a kind to rub down so fine as to form much 
mud as well as sand or gravel, the ridges are of a more clayey charac- 
ter. And where the edges of the glaciers descend to the borders of lakes 
or seas — as in the Tierra del Fuega — this mud is washed away and 
widely spread by the waters, while the gravel and sand remain nearer 
their original site ; or, finally, when the ice actually overhangs the wa- 
ter, huge fragments break off" now and then — loaded with masses of gra- 
vel and sand, or even with rocks of large size, — which fragments float 
away often to great distances and drop their stony burdens here and 
there, as they gradually melt and disappear. 

To these facts, let it be added, that recent geological researches, of a 
very interesting kind, lend to show that nearly all the elevated tracts of 
country in the temperate regions of Europe and America — in our own 
island among other localities — have been covered with glaciers at a 
comparatively recent period, (geologically speaking,) and that these gla- 
ciers have gradually retreated step by step to their present altitudes, 
hailing here for a time, and lingering there; — and we shall find reason 
to believe that traces of transported materials — moved from their origi- 
nal site by this agent also— are to be looked for on almost every geolo- 
gical formation. 

And such the geological observer finds to be in reality the case. 



270 DRIFTS IN GREAT BRITAIN. 

§ 6. Of the occurrence of such accumulations in Great Britain, and of 
their influence in modifying the character of the soil. 

Such accumulations, for example, present themselves over a large 
portion of our own island. Thus, in Devonshire, the chalk and green 
sand are so completely covered by gravels, consisting of the fragments 
of older rocks from the higher grounds, mixed with chalk-flints and 
chert, that nearly the whole of this tract possesses one common charac- 
ter of infertility, and is widely covered with downs of furze and heath 
(De La Beche.) In like manner the chalk, green sand, and plastic clay 
of a large portion of Norfolk and Suffolk, and of parts of the counties of 
Essex, Cambridge, Huntingdon, Bedford, Hertford, and Middlesex, are 
covered with till, (stiff unstratified clay,) containing large stones, (boul- 
ders,) or with gravels, in which are mixed fragments of rocks of various 
ages, which must have been brought from great distances, and perhaps 
from different directions (Lyell.) So over the great plain of the new 
red sand-stone, in the centre and west of England — in Lancashire, 
Cheshire, Shropshire, Staffordshire, and Worcestershire — drifted gra- 
vels of various kinds are widely spread. It may indeed be generally 
remarked, that over the bottoms of all our great vallies, such drifted 
fragments are commonly diffused — that upon our wider plains, they are 
here and there collected in great heaps — and that on the lower lands that 
border either shore of our island, extensive deposits of clay, sand, or gra- 
vel, not unfrequently cover to a great depth the subjacent rocks. 

The practical agriculturist will be able to confirm this remark, in 
whatever district almost he may live, by facts which have come within 
his own knowledge and observation. I shall briefly explain, by way of 
illustration, the mode in which such accumulations of drifted matter 
overlie the eastern or lower half of the county of Durham. 

The eastern half of the county of Durham reposes, to the north of the 
city of Durham, chiefly upon the coal measures, (sand-stones and shales;) 
to the south, chiefly on the magnesian lime-stone and the new-red sand- 
stone. These coal measures rise, here and there, into considerable eleva- 
tions, as at Gateshead Fell near Newcastle, and Brandon Hill near Dur- 
ham, where the rocks lie immediately beneath the surface, and are cov- 
ered by comparatively little transported matter. The magnesian hme- 
Btone, also, in many localities, starts up in the form of round hills or ridges, 
on which reposes only a poor thin soil, formed in great measure by the 
crumbling of the rock itself. Yet, generally speaking, this entire dis- 
trict is overspread with a thick sheet of drifted matter, consisting of 
clays, sands, and gravels. 

This drift is made up of three separate layers, to be observed more or 
less distinctly in taking a general survey of the county, though there are 
few spots where they can all be seen reposing immediately one over the 
other. 

1°. The upper layer consists of clays — on the higher grounds, poor, 
6tiff, yellow — on the hill-sides and slopes of the valleys, often darker in 
colour — but almost everywhere full of rounded trap boulders* from a few 

* In some parts of Northumberland these trap boulders are still more numerous. In the 
country which stretches between the north and south Tyne, the old grass fields are full ol 
them. A friend of mine informs me that in ploughing out a nine-acre field on his estate in 
that district, there were dug out and carried off no less than 900 tons of such rolled stones 
great and small ! 



DRIFT NKAH THE CITY OF DURHAM. 



271 



pounds to many tons in weight. These are generally dug up when they 
obstruct the plough, and are sold for mending the roads at about 5s. a 
ton. This clay varies in depth, from one or two, to fifty or sixty feet. 

2°. Beneath the clay occurs an accumulation of fine, generally yel- 
low, more rarely red, sand, intermixed with occasional layers and 
round hills of gravel — with frequent black streaks of rounded coal dust, 
and here and there with nests of rounded lumps of coal, from half an 
inch to five or six inches in diameter. This coal is sometimes so abun- 
dant as to be collected and sold for burning. 

The gravels, where they overlie the coal measures, consist chiefly of 
rounded, and on the upper part occasionally of large angular masses 
of coal sand-stones — with here and there a fragment of trap, of 
mountain lime-stone, or of some of the older rocks to be met with in 
the mountainous districts towards the west. Over the magnesian lime- 
stone, however, in the south-eastern division of the county, towards the 
foot of the south-eastern slope of the magnesian lime-stone hills, the gra- 
vels which exhibit in some places (Wynyard) an irregular stratification, 
contain many rounded masses of magnesian lime-stone, and even of 
new-red sand-stone — the evident debris of adjacent rocks long ago bro- 
ken up. 

3°. The undermost layer which rests immediately upon the subjacer 
rocks consists of a stiff unstratified blue clay often full of trap boulders 
but containing also occasional large rounded masses of blue lime-stone 
— and smaller pebbles of quartz, of granite, and of the older slate rocks. 
In many localities this clay is wanting, and the sands or gravels rest im- 
mediately upon the carboniferous or magnesian lime-stone rocks — while 
in some tracts, both this and the upper clay appear to degenerate into a 
stony most unmanageable clayey gravel. I am not aware that the 
large whin (trap) boulders are ever met with in the beds of sand. 

The following diagram exhibits the mode in which these drifted mate- 
rials present themselves in the neighbourhood of the city of Durham. 
The cross (+) indicates very Dearly the site of Durham on the banks of 
the river Wear. 




No. 1 represents the coal measures. 

2. The lower new-red sand-stone, here soft and pale yellow. 

3. The magnesian lime-stone rising into a high escarpment from 3 to 
6 miles south of the city. 

4. Yellow loose sand — with rolled sand-stones and coal-drift — ^^occa- 
sionally stratified. It forms the numerous picturesque round hills in the 
neighbourhood of the city, and varies from a few feet to not less than 120 
feet in thickness. 

5 is the upper clay, with boulders. N indicates Framwellgate 
Moor, where it is only a few feet thick. At S, on the southern slope of 
the escarpment, it sometimes rests immediately on the rock as here re- 



172 



THE SOILS OFTEN CHANGE FROM SAND TO CLAY. 



presented — in whicli case it is difficult to decide whether it should be con- 
sidered as the under or the upper clay — though in other spots both sand 
and clay, or gravel and clay, present themselves. 

It will at once occur to you from the inspection of this diagram, that 
the general character of the soil in the county of Durham, wherever 
such accumulations of drifted matter occur, is not to be judged from the 
nature of the rocks on which they are known to rest. 

Another fact, not unworthy of your attention, is the rapid alternations 
of light and heavy soil, of sands or gravels and clays, which present 
themselves in the same district, I may say in the same farm, and often 
in the same field. This arises from the irregular thickness of the de- 
posit of sand or gravel over which the upper clay rests. The surface 
of this sand is undulating, as if it had formed a country of round hills 
before the clay was deposited upon it. This appears in the following 
diagram, which represents the way in which the several layers are seen 
to occur in the Crindon cut on the Hartlepool railway : — 




Here 1 is the magnesian lime-stone, not visible ; 2, the under clay, 
with boulders ; 3, the sand rising in round hills, and here and there 
piercing to the surface ; and 4, the upper boulder clay. 

In the county of Durham it is a very usual expression that the tops 
of the hills are light turnip soil — but that they fall off" to day. Both the 
meaning and the cause of this are explained by the above diagram. 

Nor is this mode of occurrence rare among the alternate sands and 
clays of which the superficial accumulations in various parts of the 
country consist. Nearly the same circumstances give rise to the rapid 
changes so frequently observed in the character of the soil, as we pass 
from field to field, not in this county only, but in various other parts of 
our island. 

§ 7. Hoio far these accumulations of drift interfere ivith the general 
deductions of Agricultural Geology. 

Thus it appears, that over the eastern half of the county of Dur- 
ham, and over large portions of other counties, the soils are found to 
rest upon and to derive their character from accumulations of drifted 
materials more or less different in their nature from the rocks that lie 
beneath. 

But in the preceding lecture I have endeavoured to show you that 
soils are derived from the rocks on which they rest, and to impress upon 
you the close general relation which exists between the kind of rocks of 
which a country is composed, and the kind of soils by which its surface 
is overspread. 

How are these apparent contradictions to be reconciled ? How is any 



DRIFT MIXED UP WITH THE DETRITUS OF THE SPOT. 273 

degree of order to be evolved out of this apparent confusion? Are the 
general indications of agricultural geology (Lecture xi., §8, ) still, in any 
degree, to be relied upon ? 

They are, and for the following, among other reasons : 

1°. It is still generally true that where a considerable extent of coun- 
try rests upon any known rock, the soil in that district derives its usual 
character from the nature of that rock. Thus though large portions of 
Cheshire and Lancashire are covered with drift, yet the soil of these 
counties, taken as a whole, has the general characters of the soils of 
she new-red sand-stone, which in that part of England is so largely de- 
veloped. 

2°. Where the drift overspreads any large area, it is found to become 
gradually mixed up with the fragments, large and small, of the rocks 
upon which it reposes. Thus in the neighbourhood of Durham, the 
round hills of sand and gravel with intermingled coal consist in great 
part of the ruins of the sand-stones of the country itself — while the 
clays, no doubt, are partly derived from the shale beds which occur in- 
termingled with the sand-stones of the same coal measures. Hence the 
soils of the northern half of this county, in general, still partake of the 
usual qualities of those of the coal measures and mill-stone grit (pp. 
249 and 250). In the western and higher part of the district they lie 
more immediately on the rocks from which they have been derived, 
while on the eastern half they rest on a mixture of the accumulated 
ruins of the same rocks, which have been transported by natural agents 
to a greater or less distance from their natural site. 

It is true that there are mixed up with these many portions of other 
rocks brought from a still greater distance, but these bear but a small 
proportion lo the entire mass, and hence have, generally speaking, but 
little influence in altering the mineral character of the whole. 

3°. It may indeed be stated as generally true, that the greater propor- 
tion of the transported materials which lie upon any spot has been 
brought only a comparatively small distance. Thus the sands and gra- 
vels in the county of Durham — to the west of the magnesian lime- 
stone — consist chiefly of the fragments of the coal measures. East and 
south of the magnesian lime-stone escarpment (diagram, p. 271), they 
become mixed with rounded masses of this lime-stone. On the new- 
red sand-stone of the south-east of the county, they consist chiefly of 
magnesian lime-stone mixed with fragments of the red sand-stone— 
and on crossing the Tees, the debris of the lias hills begins to appear 
among them. 

]n countries, therefore, where drifted sands and gravels prevail on the 
surface, they generally consist of the fragments of rocks which lie at no 
great distance — generally towards the higher ground — the natural ten- 
dency being for the debris of one kind of rock, or of one formation, to 
overlap to a greater or less extent the surface of the adjoining rock or 
formation. By this overlapping, the geographical position of a given 
soil is removed lo a greater or less distance beyond the line indicated by 
the j§-eoZo^?Va^ position of the rocks from which it is derived. Thus, a 
coal measure soil may overspread part of the rhagnesian lime-stone — 
a red sand-stone soil may partially cover the lias, and so on — the general 



274 GENERAL DEDUCTIONS OF GEOLOGY STILL TRUE. 

characters and distinctions of the soil peculiar to each rock being still 
preserved beyond the spaces upon which they have been accidentally 
intermingled. 

4°. To this, and to each of the other statements above made, there are 
many local exceptions. For instance, what is true of sands and gravels, 
will not so well apply to the fine mud of which many clays are formed. 
Once commit these to the water, and if it has any motion, they may be 
transported to very great distances from their original site. Rivers, 
lakes, and seas, are the agents by which these extensive diffusions are 
effected. The former produce what are called alluvial formations or de- 
posits; which are generally rich in all the inorganic substances that 
plants require, and hence yield rich returns to the agricultural labourer. 
They are usually, however, disiinguished, and their boundaries marked, 
by the geologist — so that the soils which repose upon them do not con- 
tradict any of the general deductions he is prepared to draw, in regard to 
the general agricultural capabilities of a country^ from the kind of rocks 
of which it consists. 

Thus though the occurrence of extensive fields of drift over various 
parts of almost every country, does throw some further diflSculty over 
the researches of the agricultural geologist, and requires from him the 
application of greater skill and caution before he pronounce with cer- 
tainty in regard to the agricultural capabilties of any spot before he visit 
it — yet it neither contradicts the general deductions of the geologist nor 
the special conclusions he would be entitled to draw in regard to the 
ability of any country, when rightly cultivated, to maintain in comfort 
a more or less numerous population. The political economist may still, 
by a survey of the geological map of a country, pronounce with some 
confidence to what degree the agricultural riches of that country might 
by industry and skill be brought — and which districts of an entire conti- 
nent are fitted by nature to maintain the most abundant population. 
The intending emigrant may still, by the same means, say in what new 
land he is most likely to find a propitious soil on which to expend his 
labour — or such mineral resources as will best aid his agricultural pur- 
suits ; — while a careful study of the geological map of his own country 
will still enable the skilful and adventurous farmer to determine in what 
counties he will meet with soils that are suited to that kind of practice 
with which he is most familiar — or which are likely best to reward 
him for the application of the newest and most a])proved methods of 
culture. 

Still there are some aids to this kind of knowledge yet wanting. We 
have geological maps of all our counties, in which the boundaries of the 
several rocky formations are more or less accurately pointed out, and 
from these maps, as we have seen, much valuable agricultural informa- 
tion may be fairly deduced. We have also agricultural maps of many 
counties, compiled with less care, and often with the aid of little geolo- 
gical knowledge, as that of Durham in Bailey's ' View of the Agricul- 
ture of the County of Durham,' published in 1810. But agriculture 
now requires geological maps of her own — which shall exhibit not only 
the limits of rocky formations, but also the nature and relative extent 
of the superficial deposits (drifts), on which the soils so often rest, and 
from which they are not unfrequenily formed. These would afford a 



AGRICULTURAL MAPS ACCUMULATIONS OF PEAT. 275 

sure basis on which to rest our opinions in regard to the agricultural ca- 
pabilities of the several parts of a county in which, though the rocks are 
the same, the soils may be very different. To the study of these drifted 
materials, in connection with the action of ancient glaciers (p. 269), the 
attention of geologists is at present much directed, and from their labours 
agriculture will not fail to reap her share of practical benefit — the geolo- 
gical survey, also, so ably superintended by Mr. De La Beche, is col- 
lecting and recording much valuable information in regard to the agri- 
cultural geology of the southern counties — but it is not unworthy the con- 
sideration of our leading agricultural societies — whether some portion of 
their encouragement might not be beneficially directed to the preparation 
of agricultural maps, which should represent, by different colours, the agri- 
cultural capabilities of the several parts of each county, based upon a 
knowledge of the soils and sub-soils of each parish or township, and of 
the rocks, whether near or remote, from which they have been severally 
derived. 

Before leaving this subject, I will call your attention to one practi- 
cal application of this knowledge of the extensive prevalence of drifts, 
wjiich is not without its value. Being acquainted with the nature of the 
rocks in a country, and with its physical geography — that is, which of 
these rocks form the hills, and which the valleys or plains — we can pre- 
dict, in general, that the materials of the hills will be strewed to a greater 
or less distance over the lower grounds, and that these lower soils will 
thus be more or less altered in their mineral character. And when the 
debris of the hills is of a more fertile character than that of the rocks 
which form the plains, that the soils will be materially improved by this 
covering: — the soil of the mill-stone grit, for example, by the debris of 
the mountain lime-stone, or of a decayed green-stone or a basalt. On 
ihe other hand, where the higher rocks are more unfruitful, and the low 
lands are covered with sterile drifted sands brought down from the more 
elevated grounds — a knowledge of the nature of the subjacent rock may 
at once suggest the means of ameliorating and improving the unpromis- 
ing surface-drift. Thus the loose sand of Norfolk is fertilized by the 
subjacent chalk marl; and even sterile heaths (Hounslow), on which 
nothing grew before, have, by this means, been made to produce luxu- 
riant crops of every kind of grain. 

§ 8. Of sujyerjicial accumulations of Peat. 

Of superficial accumulations, that of peat is one which, in the United 
Kingdom, covers a very large area. In Ireland alone, the extent of bog 
is estimated at 2,800,000 acres. None of the drifted materials we have con- 
sidered, therefore, would appear so likely to falsify the predictions of the 
geologist, who should judge of the soils of such a country from informa- 
tion in regard to the rocks alone on which they rest — from a geological 
map for example — as the occurrence of these peat bogs. Yet there are 
certain facts connected with the formation of peat, which place him in 
some measure on his guard in reference even to accumulations of vege- 
table matter such as these. 

1°. There is a certain range of temperature within which alone peat 
seems capable of being produced. Thus, at the level of the sea, it is 
never found nearer the equator than between the 40° and 45° of latitude; 



276 WHERE PEAT IS TO BE EXPECTED. 

while its limit towards the poles appears to be within the 60lh degree. 
It is a product, therefore, chiefly of the temperate regions. 

Still, on the equator itself, at a sufficient altitude above the sea, the 
temperature may be cool enough to permit the growth of peat. Hence, 
though on the plains of Italy no peat is formed, yet, on the higher Ap- 
penines, it maybe here and there met with, among the marshy basins, 
and on the undrained mountain sides. 

2°. The occurrence of stagnant water is necessary for the production 
of peat. Hence, on impervious beds of clay, through which the rains 
and springs can find no outlet, the formation of peat may be expected. 
Thus on the Oxford clay repose the fens of Lincoln, Cambridge and 
Huntingdon (p. 245). On impervious rocks also, peat bogs form for a 
similar reason. The new-red sand-stone is occasionally thus impervi- 
ous, and on it, among other examples, repose the Chat moss, the tract of 
peat, mostly in cultivation, which lies west of a line drawn between 
Liverpool and Preston, and the large extent of boggy country which 
stretches round the head of the Solway Firth. On the old red sand- 
stone, the mountain lime-stone, the slate, and the granite rocks, much 
peat occurs, and it is on these latter formations that the extensive bogs of 
Scotland and Ireland chiefly rest. 

But though these two facts are of some value to the politician and to 
the geologist in indicating in what countries and on what formations peat 
may be expected to occur, yet they are of comparatively little impor- 
tance to the practical agriculturist. It is of far more consequence to 
him that the moment he casts his eye upon the face of a country he can 
detect the presence or absence of peat — that none of the perplexities 
which beset the nature and origin of other superficial accumulations at- 
tach to this — that he can, at once, judge both of its source and of its agri- 
cultural capabilities. Though produced on a given spot, because rocks 
of a certain character exist there, yet its origin is always the same — its 
qualities more or less uniform, — the improvement of which is susceptible 
in some measure alike, — and the steps by which that improvement is to 
be effected, liable to variation, chiefly according as this or that amelio- 
rating substance can be most readily obtained. 



LECTURE XIII. 

Exacl chemic&l constitution of soils — their organic constituents — Analysis of soils — Compo* 
sition of certain characteristic soils — Physical characters of soils. 

1j? the two preceding lectures we have considered the general consti- 
tution and origin of soils, and their relation to the geological structure of 
the country in which they are found, and to the chemical composition of 
the rocks on which they rest. We have also discussed some of the 
causes of those remarkable differences Which soils are known to present 
in their relations to practical agriculture. But a ntore intimate and pre- 
cise acquaintance with the chemical constitution of soils is not unfre- 
quently necessary to a complete understanding of the causes of these dif- 
ferences — of the exact effect which its chemical conslitution has upon the 
fertility of a soil — and of the remedy which in any given circumstances 
ought to be applied. 

Some persons have been led to expect too much from the chemical 
analysis of a soil, as if this alone were necessary at once to explain all its 
qualities, and to indicate a ready method of imparting to it every desir- 
able quality, — while others have as far depreciated their worth, and have 
pronounced them in all cases to be more curious than useful. — [Boussin- 
gault, * Annal. de Chim. et de Phys.' Ixvii., p. 9.] The truth here, as 
on most other subjects, lies in the middle between these extreme opinions. 

If you have followed me in the views I have endeavoured to press upoii 
you in regard to the necessity of inorganic food to plants — which food 
can only be derived from the soil, and which must vary in kind and 
quantity with the species of crop to be raised, — you will at once perceive 
that the rigorous analysis of a soil may impart most valuable knowledge 
to the practical man in the form of useful suggestions for its improvement. 
It may indeed show that to apply the only available substances to the 
soil which are capable of remedying its defects, would involve an expense 
for which, in existing circumstances, the land could never give an equiva- 
lent return. Yet even in this latter case the results of analysis will not be 
without their value to the prudent man, since they will deter him from, 
adding to his soil what he knows it already to contain, and will set him 
upon the search after some more economical source of those ingredients 
which are likely to benefit it most. 

It will be proper, therefore, to turn our attention briefly to the conside- 
ration of the exact chemical constitution of soils. 

§ 1. Of the exact nature of the organic constituents of soils, and of the 
mode of separating them. 
We have already seen in Lecture XL, p. 229, that all soils contain a 
greater or less admixture of organic — chiefly vegetable — matter, the 
total amount of which may be very nearly determined by burning the 
dried soil at a red heal till all blackness disappears (p. 233). But this 
vegetable matter consists of several different chemical compounds, the 
nature and relative weights of which it is occasionally of consequence to 
be able to determine. 
24 



278 NATURE OF THE ORGANIC CONSTITUENTS OF SOILS. 

1°. Humus. — The general name of humus is given to the fine, brown 
light powder which imparts their richness to vegetable moulds and gar- 
den soils. It is formed from the gradual decomposition of vegetable 
matter, exists in all soils, forms the substance of peat, and consists of a 
mixture of several different compounds which are naturally produced 
during the decay of the different parts of plants. It is distinguished into 
mild^ sour, and coaly humus. 

The mild gives a brown colour to water, but does not render it sour, 
gives a dark brown solution when boiled with carbonate of soda, evolves 
jimmonia when heated with caustic |)otash or soda or with slaked lime, 
and leaves an ash when burned which contains lime and magnesia. 
The soiir gives, with water, a brown solution of a more or less sour 
taste, [or reddens vegetable blues— see page 45.] This variety 13 
less favourable to vegetation than the former, and indicates a want of 
lime in the soil. The coaly humus gives little colour to water or to a 
hot solution of carbonate of soda, leaves an ash which contains little 
Hme, occurs generally on the surface of very sandy soils, and is very un- 
fruitful. It is greatly ameliorated by the addition of lime or wooc^ 
ashes. 

2°. Humic acid. — When a fertile soil or a piece of dry peat is boiled 
■with a solution of the common carbonate of soda of the sliops, a brown 
solution, more or less dark, is obtained, from which, when diluted muri- 
atic acid (spirits of salt) is added till the liquid has a distinctly sour 
taste, brown flocks begin to fall. This brown floeky matter is humic add' 

3°. Ulmic acid. — If, instead of a solution of carbonate of soda, one 
of caustic ammonia, (the hartshorn of the shops,) be digested upon the soil 
or peat by a gentle heat, a more or less dark brown solution is obtained, 
which, on the addition of muriatic acid, gives brown flocks as before, 
but which now consists o^ ulmic acid. 

These two acids combine with lime, magnesia, alumina, and oxide of 
iron, forming compounds (salts) which are respectively distinguished by 
the names of hiimates and ulmaies. They probably both exist, ready 
formed, in the soil in variable proportions, and in combination with on© 
or more of the earthy substances above mentioned — lime, alumina, &e. 
They are produced by the decay of vegetable npatter in the soil, which 
decay is materially facilitated by the presence of one or other of these 
eubstances, and by lime especially — on the principle that the formation 
of acid compounds is in all such cases much promoted by the presence 
of a substance with which that acid may combine. They predispose 
organic substances to the formation of such acids, and consequently to 
the decomposition by which tbey are to be produced. These two acido* 
consist respectively of 

Humic 9.^1^. Ulqaic acid. 

Carbon 6.3 57 

Hydrogen 6 4^- 

Oxygen 31 38^ 

100 100 

Some writers upon agriculture have supposed that these acids con- 
tribute very materially to the support of growing plants. But Liebig 



CRENIC AND APOCRENIC ACIDS. 279 

has very properly objected to this opinion,* that they are so very sparingly 
soluble in water that we cannot suppose them to enter directly into the 
roots — even were all the water they absorb to be saturated with them — 
in such quantity as to contribute in a great degree to the organic matter 
contained in almost any crop.f 

We have indeed seen reason to conclude on other grounds, that only a 
small, though a variable, proportion of the carbon of plants is derived 
from the soil, yet of this proportion a certain quantity may enter by the 
roots in the form of one or other of these acids, or of their earthy com- 
pounds. They are readily soluble in ammonia; and animal manures 
which give off this compound in the soil may therefore facilitate their 
entrance into the roots of those plants which are cultivated by the aid of 
such manures. They are also soluble in carbonate of potash and car- 
bonate of soda, which are contained in wood ashes and in the ash of 
weeds aj;id of soils which are pared and burned. When these substan- 
ces, therefore, are applied to the land, they may combine with, and, 
among their other beneficial modes of action, may serve to introduce, 
these acids in larger quantity into the plant. 

When exposed to the air, the humates and ulmales contained in the 
soil undergo decomposition, give off carbonic acid, and are changed into 
carbonates. The admission of air into the soil facilitates this decompo- 
sition, which is supposed to be continually going forward — and it is in the 
form of this gas that plants are considered by some to imbibe the largest 
portion of that carbon for which they are indebted to the soil. 

4°. Crenic and Aprocrenic acids. — When soils are digested or washed 
with hot water, a quantity of organic matter is not unfrequently dissolved, 
which imparts to the water a brownish yellow colour. When the solu- 
tion is evaporated to dryness, there remains besides the soluble saline 
substances of the soil, a variable portion of brown extractive looking 
matter also, which is a mixture of the two acids here named, with the 
ulmic and humic — all in combination with lime, alumina, and other bases. 
When this residue is dried at 230° F., the two latter acids, and their 
compounds, become insoluble, while the crenales and apocrenates, more 
especially the former, remain soluble in water, and may be separated 
by washing with this liquid. 

These acids also are formed in the soil during the decay of vegetable 
matter. They are distinguished from the two previously described by 
containing nitrogen as an essential constituent, and by forming compounds 
with lime, <kc., which are, for the most part, readily soluble in water. 
Hence they will both prove more nourishing to plants — in virtue of the 
nitrogen they contain — and in consequence of their solubility, will be able, 
where they exist, to enter more readily, and in greater abundance, into 
the roots than either the ulmic or the humic acid. 

Owing to this solubility, also, they are more readily washed out of the 
soil by the rains, and hence are rarely present in any considerable quan- 

* Organic Chemistry applied la Agriculture^ first edition, pp. 11 and 12. 

t Ulmic acid requires 2500 times its weight of water to dissolve it— ulmate of lime 2000 
times, and ulmate of alumina 4200 times — but all are still less soluble after they have been 
perfectly dried, or exposed to the action of a hard winter's frost. The ulmates of potash, 
soda, and alumina, are all dissolved in water with considerable ease. 



280 OTHER ORGANIC COMPOUNDS IN THE SOIL. 

tity in specimens of soil which are submitted to analysis. They are fre- 
quently, however, met with in springs and in the drainings of the land. 
They have even been found in minute quantity in rain-water,* it is pro- 
bable that they ascend into the air in very small proportion with the 
watery vapour that rises. This exhibits another form, therefore, in 
which the rains may minister to the growth of plants (see page 36). 

•Both acids form insoluble compounds with the peroxide of iron — and 
hence are found in combination with many of the ochrey deposits from 
ferruginous springs, and with the oxide of iron by which so many soils 
are coloured. The apocrenic acid has also a peculiar tendency to com- 
bine with alumina, with which it forms a compound insoluble in water, 
and in this state of combination it probably exists not unfrequently, espe- 
cially in clayey soils. 

When heated with newly slaked quick-lime these acids give off am- 
monia and carbonic acid. By the action of the air, and of Urge in the 
soil, they are probably decomposed in a similar manner, though with 
much less rapidity. 

5°. Mudesous acid is another dark brown acid substance, which is also 
produced naturally in the soil. It resembles the apocrenic, in having 
a strong tendency to combine with alumina. In union with this acid it 
is slowly washed out of the soil by the rains, or fillers through it when 
the water can find an outlet beneath. This is seen to be the case in some 
of the caves on the Cornish coast, where the waters that trickle through 
from above have gradually deposited on their roof and sides a thick in- 
crustation of mudesite of alumina.\ 

Besides these acids, it is known that the malic and the acetic (vine- 
gar) are occasionally produced in the soil during the slow decay of vege- 
table matter of different kinds. It is probable that many other analo- 
gous compounds are likewise formed — which are more or less soluble in 
water, and more or less fitted to aid in the nourishment of plants. There 
is every reason to believe, indeed, that organic substances in the soil pass 
through many successive stages of decomposition, at each of which they 
assume new properties, and become more or less capable of aiding in 
the support of living races. The subject is difficult to investigate, be- 
cause of the obstacles which lie in the way of exactly separating from 
each other the small quantities of the different organic compounds that 
occur mixed up together in the soil. But it seems quite clear, that while 
some agricultural chemists have erred in describing the ulmic and hu- 
mic acids as the immediate source of a large portion of the carbon of 
plants, others have no less misstated — as I apprehend — the true course 
of nature, who deny any direct influence to these and other substances 
of vegetable origin, and limit their use in the soil to the supply of car- 
bonic acid only, which, on their ultimate decomposition, they are capa- 
ble of yielding to the roots. The resources of vegetable life are not so 
limited; but as the human stomach can, and does, on occasion, convert 
into nourishment many different compounds of the same elements, — so, 
no doubt, many of those organic compounds which are produced in the 
soil, or in fermenting manure during the decay of animal and vegetable 

• Fiirsten zu Salm.Horstmar. Poggend. Armed, liv., p. 254. 
t Known to mineralogiats under the name of Pigotite. 



SEPARATION OF THESE ORGANIC SUBSTANCES. 281 

bodies, — when once admitted, in consequence of their solubility, into the 
circulating system of plants, — are converted into portions of their sub- 
stance, and really do minister to their natural growth. 

Separation of these Organic Constituents. — 1°. "When on washing 
with hot water a soil imparts a colour to the solution, the liquid must be 
filtered and evaporated, to perfect dryness. On treating with water 
what remains after the evaporation, the humic acid and humates remain 
insoluble, while the crenic and apocrenic acids are taken up by the wa- 
ter along with the soluble saline matter which the soil may have con- 
tained. By evaporating this second solution to perfect dryness, weigh- 
ing the residue, and then heating it to dull redness in the air, the loss 
will indicate something more than the quantity of these acids present in 
the soil. By burning the dried insoluble matter, also, the quantity of 
humic acid present in it may in like manner be determined. 

2°. After being washed with pure water, the soil is to be boiled with 
a solution of carbonate of soda, repeated once or twice as long as a brown 
solution, more or less dark, is obtained. Being filtered, and then ren- 
dered. sour by muriatic acid, brown flocks fall, which being collected on 
the filter, perfectly dried and weighed, give the quantity of humic acid 
in the soil. As this dry humic acid generally contains some earthy 
matter, it is more correct to burn it, and to deduct the weight of the ash 
which may be left. 

3°. The insoluble (coaly) humus still remains in the soil. On boiling 
it now in a solution of caustic potash for a length of time, and till a fresh 
solution ceases to become brown, the coaly humus is entirely dissolved— 
being converted according to Sprengel into humic acid. The addition 
of muriatic acid to this solution, till it has a sour taste, throws down the 
humic acid in the form of brown flocks, which may be collected, dried, 
and weighed as before. 

4°. If there be any mudesite of alumina in the soil, it is also dis- 
solved by the potash, but is not thrown down when the solution is ren- 
dered sour by muriatic acid. The entire weight of organic matter in the 
soil being therefore determined by burning it in the air, after being 
perfectly dried, the difference between this weight and the sum of those 
of the humic acid and insoluble liumus will be the proportion of the 
other acids present. Thus, if, by burning in the air, the soil lose 6 per 
cent., and give 2 per cent, of humic acid, and 2 of insoluble humus, there 
remain 2 per cent, for other organic substances in the soil. 

In general, it is considered sufficient to ascertain only the whole loss 
by burning, and the quantity taken up by carbonate of soda, the propor- 
tion of the other substances present being in most cases so small as to be 
capable of being precisely estimated by great precautions only. 

§ 2. On the exact chemical constitution of the earthy part of the soil. 

In reference to the general origin of soils-^to their geological rela- 
tions — and to the simplest mode of classifying them, — I have shown you 
that the earthy part of nearly all soils consists essentially of sand, clay, 
and lime (p. 230). But in reference to their chemical relations to the 
plants which grow, or may be made to grow, upon them, it is necessary, 
as you are now aware, to take a more refined and exact view of their 



262 WHY REFINED ANALYSES ARE NECESSARY. 

constitution. This will appear by referring to three important princi- 
ples established in the preceding lectures. 

1°. That the ash of plants generally contains a certain sensible pro- 
portion of ten or twelve different inorganic substances (pp. 216 to 221). 

2°. That they can, in general, only derive these substances from the 
soil, which must, therefore, contain them (p. 181). And — 

3°. That the fertility of a soil depends, among other circumstances, 
upon its ability to supply readily and in sufficient abundance all the in- 
organic substances which a given crop requires (p. 228.) 

Now the quantity of some of these substances which is necessary to 
plants is so very small, that nothing but a refined analysis of a soil is 
capable, in many cases, of determining whether they are present in it or 
not — much less of explaining to what its peculiar aefects or excellencies 
may be owing — what ought to be added to it in order to render it more 
productive — or why certain remarkable effects are produced upon it by 
the addition of mineral or animal manures. 

Thus, for example, half a grain of gypsum in a pound of soil indicates 
the presence of nearly two c wt. in an acre, where the soil is a foot deep,— 
a quantity much greater than need be added to a soil in which gypsum 
is almost entirely wanting, in order to produce a remarkable luxuriance 
in the red clover crop. In 100 grains of the soil, this quantity of gyp- 
sum amounts only to seven-thousandths of a grain — (i-^^» or 0*007 
grs.)_a proportion which only a very carefully conducted analysis 
would be able to detect, and yet the detecting of which may alone be able 
to explain the unlike effects which are seen to follow the application of 
gypsum to different soils. 

Again, the phosphoric acid is a no less necessary constituent of the 
soil than the sulphuric acid contained in gypsum. This acid is gener- 
ally in combination either with lime, with oxide of iron, or with alu- 
mina—and, as it is much more difficult even to detect than the sulphuric 
acid, requires more care and skill to determine its quantity with any 
degree of accuracy, — and is generally present even in fertile soils in a 
still smaller proportion — it is obvious that safe and useful conclusions can 
be drawn only from such analyses as have been made rigorously, accord- 
ing to the best methods, and with the greatest attention to accuracy. 

There are cases, no doubt, where a rough analysis may be of use, 
where the cause of peculiarity is at once so obvious that further research 
is unnecessary — as where mere washing with water dissolves out a 
noxious substance, such as sulphate of iron (green vitriol). But such 
cases are comparatively rare, and it more frequently happens, that the 
cause of the special qualities of a soil only begins to manifest itself when 
a carefully conducted analysis approaches to its close. I shall, therefore, 
briefly describe to you the methods to be adopted, in order to arrive at 
these more accurate experimental results. [As these methods of analysis 
involve considerable detail, I have transferred them to the Appendix.— 
See Appendix^ p. 25.] 



EXACT CONSTITUTION OF SOME FERTILE SOILS. 2^3 

§3. Of the exact chemical constitution of certain soils^ and of the results 
» to be deduced from them. 

But the importance of this attention to rigorous analysis will more 
clearly appear, if I exhibit to you the thnstituiion of a few of the nume- 
rous soils analyzed by Sprengel, in connection with the agricultural quali- 
ties and capabilities by which they are severally distinguished. 

The following analyses are selected from a much greater number made 
by Sprengel, and embodied in his work on soils, " JDie Bodenkunde." 

I. FERTILE SOILS. 

Soils are fertile which contain a sufficient supply of all the mineral 
constituents which the plants to be grown upon them are likely to re- 
quire. 

1°. Pasture.— The following numbers exhibit the constitution of the 
surface soil in three fertile alluvial districts of Hanover, where the land 
has been long in pasture- 
Soil near From the banks of the Weser, 
Osterbruch. near Hoya. near Weserbe. 

Silica, Quartz, Sand, and Silicates. 84-510 71-849 83-318 

Alumina 6-435 9-350 3-085 

Oxides of Iron 2-395 5-410 5-840 

Oxide of Manganese .... 0-450 0-925 0-620 

Lime 0-740 0-987 0-720 

Magnesia 0-525 0-245 0-120 

Potash and Soda extracted by water 0-009 0-007 0-005 

Phosphoric Acid 0-120 0-131 0-065 

Sulphuric Acid .... , 0-046 0-174 0-025 

Chlorine in common Salt . . 0-006 0-002 0-006 

Humic Acid 0-780 1-270 0-800 

Insoluble Humus .... 2-995 7-550 4-126 

Organic matters containing Nitrogen 960 •2-000 1-2-20 

Water ...... . . 0-029 0-100 0-050 



100 100 100 

These soils had all been long in pasture, the second is especially cele- 
brated for fattening cattle when under grass. It will be observed that in 
none of them is any of the mineral ingredients wholly wanting, though 
in alt the qnantity of potash and soda capable of being extracted by 
water is very small. This is ascribed to the fact of their having been 
long In pasture, during which the supply of these substances is gradually 
withdrawn by the roots of the grasses. It is well known how, in our or- 
dinary soils, gr^ss is often renovated — how the mosses, especially, are de- 
stroyed — by a dressing of wood ashes, which owe their effect to the alkali 
they contain. In the above soils the gradual decomposition of the sili- 
cates would continue to supply a certain portion of alkaline matter for an 
indefinite period of time. 

You will perceive that the soil which is the most celebrated for its fat- 
tening power, is also the richest in alumina, lime, phosphoric acid, sul- 
phuric acid, and vegetable matter. 



284 



THE SOIL OF RICH ARABLE LANDS. 



2°. Arable, — The following table exhibits the constitution of three 
soils, celebrated for yielding successive crops of corn for a long period 
without manure. 



Silica and fine Sand 

Alumina 

Oxides of Iron . . 

Oxide of Magnesia . 



1- • 

From Nebtsein, 
near Olmutz, 
in Moravia. 

. 77-209 

. 8-514 

. 6-592 

. 1-520 



Lime 0-927 

Magnesia 1-160 

Potash chiefly combined 

with Silica .... 0-140 
Soda, ditto .... 0-640 
Phosphoric Acid combined 
with Lime and Oxide of 

Iron 0-651 

Sulphuric Acid in gypsum 0-011 
Chlorine in common salt. 0*010 
Carbonic Acid united to the 

Lime — 

Humic Acid . . . . 
Insoluble Humus . . . 
Organic substances con- 
taining Nitrogen 



0-978 
0-540 

1-108 



2. 

From the banks of the 

Ohio, North America. 

Soil. Subsoil. 

87-143 94-261 

5-666 1-376 

2-220 2-336 

0-360 1-200 

0-564 0-243 

0-312 0-310 

^•^2^ I 240 
0-025 i " ^^" 



0-060 trace 

0-027 0-034 

0-036 trace 

0.080 — 

1.304 — 

1.072 — 

1-011 — . 



3. 

From the polde, 

of Alt-Arenbergr 

in Belgium. 

64-517 

4-810 

8-316 

0-800 

Carbof - ^„„ 
Lime 9-403 

Carb.of _ 
Mag. 10-361 

5 0-100 
) 0-013 



1-221 

0-009 
0-003 



0-447 



100 



100 



100 



100 



Of these soils, the first had been cropped for 160 years successively, 
without either manure or naked fallow. The second was a virgin soil, 
celebrated for its fertility. The third had been unmanured for twelve 
years, during the last nine of which it had been cropped with beans 
— barley — potatoes — winter barley and red clover — clover — ^winter bar- 
ley — wheat — oats — naked fallow. 

Though the above soils differ considerably, as you see, in the propor- 
tions of some of the constituents, yet they all agree in this-^tbat they are 
not destitute of any one of the mineral compounds, which plants necessa- 
rily require in sensible quantity. You will also observe how compara- 
tively small a proportion of vegetable matter, less than half a per cent., 
is contained in the fertile Belgian soil — a fact to which I shall by-and- 
by recall your attention. 

3°. Soils which have a natural source of fertility. — Some soils, which 
by their constitution are not fitted to exhibit any great degree of fertility, 
or for a very long period, are yet, by springs or otherwise, so constantly 
supplied with soluble saline, and other substances, as to enable them to 
yield a ^succession of crops, without manure, and without apparent dete- 
rioration. Such is the case with the following soil from near Rothen- 



SPRINGS OFTEN ENRICH THE SOILS. 285 

felde, in Osoabruck, which gives excellent crops, though manured only 
ouce in 10 or 12 years. 

Silica and coarse QuarlE Sand .... 86*200 

Alumina 2-000 

Oxides of Iron and a little Phosphoric Acid . 2*900 

Oxide of Manganese 0*100 

Carbonate and a little Phosphate of Lime . 4*160 

Carbonate of Magnesia 0*520 

Potash and Soda 0*035 

Phosphoric Acid 0*020 

Sulphuric Acid 0-021 

Chlorine 0*010 

Humic Acid 0-544 

Insoluble Humus 3-370 

Organic matter containing Nitrogen . . . 0-120 



100 

You will see that, although in this soil all the inorganic substances are 
really present, yet the potash and soda, the phosphoric and sulphuric 
acids, and the chlorine, are hot in such abundance as to justify us in ex- 
pecting it to grow any long succession of crops, without exhibiting the 
usual evidences of exhaustion. But it lies on the side of a hill which con- 
tains layers of lime-stone and marl, through which the surface waters 
find their way. These waters afterwards rise into the soil of the field, 
impregnated with those various substances of which the soil is in want, 
and thus, by a natural manuring, keep up a constant supply for each suc- 
ceeding crop. 

This example is deserving of your particular attention, inasmuch as 
there are many soils, in climates such as ours, which are yearly refresh- 
ed from a similar source. Few spring waters rise to the surface which 
are not fitted to impart to the soil some valuable ingredient, and which, if 
employed for the purposes of irrigation, would not materially benefit 
those lands especially on which our pasture grasses grow. The same 
may also be said of the waters which are carried off in some places so 
copiously by drains. Whether these waters rise from beneath in springs, 
or, falling in rain, afterwards sink through the soil, they in either case 
carry into the brooks and rivers much soluble matter, whi6h the plants 
would gladly extract from them. On sloping grounds it would be a 
praiseworthy economy to arrest these waters, and, before they escape, 
to employ them in irrigation. 

The fact that nature thus on many spots brings up from beneath, or 
down from the higher grounds, continual accessions of new soluble mat- 
ter to the soil, will serve to explain many apparent anomalies, and to ac- 
count for the continued presence of certain substances in small quantity, 
although year by year portions of them are carried off the land in the 
crops that are reaped, while no return is made in the shape of artificial 
manure. It will also in some instances account for the fact that, after a 
hard cropping, prolonged until the soil has become exhausted, a few 
years' rest will completely re-invigorate it, and render it fit to yield 



286 



IMPORTANCE OF DKPTH OF SOIL» 



new returns of abundant corn. Other causes, as we shall hereafter see^ 
generally operate in bringing about this kind of natural recovery, but 
there can be no question that in circumstances such as I have now 
adverted to, this recovery may be effected in a much shorter period 
of time. 

4°. Importance of depth and uniformity of soil. — If the surface soil be 
of a fertile quality, ample returns will be sure from many cultivated 
crops. But where the subsoil is similar in composition to that of the 
surface — not only may the fertility of the land be considered as almost 
inexhaustible, but those crops also which send their roots far down will 
be able permanently to flourish in it. This fact is illustrated by the 
composition of the following soils from the neighbourhood of Bruns- 
wick :— 

1. 2. 



Soil. 

Silica and fine Quartz Sand . 94-724 

Alumina 1-638 

Oxides of Iron . . . . 7 l-QQQ 

Oxides of Manganese . . y 

Lime . . . . . . . . 1-028 

Magnesia trace 

Potash and Soda ..... 0-077 

Phosphoric Acid 0-024 

Sulphuric Acid 0-010 

Chlorine 0-027 

Humic Acid . ..... 0-302 

Insoluble Humus .... 0-210 



Subsoil. 


Subsoil. 


97-340 


90-035 


0-806 


1-976 


5 1-126 
I 0075 


5-815 


0-240 


0-296 


0-022 


0-095 


0-115 


0-112 


300 


0-015 


0-098 


trace 


1-399 


trace 


trace 


0-135 


— 


^~* 


— 



100 



100 



100 



The first .of these soils produced excellent crops of all deep-rooted 
plants — lucerne, sainfoin (esparsette), hemp, carrots, poppies, dec. — and 
with the aid of gypsum, red clover, and leguminous plants (vetches, 
peas, and beans), in great luxuriance. The former of these facts is ex- 
plained by the great similarity in constitution which exists between the 
surface and the under soils. To deep-rooted plants also the magnesia, 
in which the surface is deficient, is capable of being supplied by the under 
soil. The effect of the gypsum is accounted for by the almost total ab- 
sence of sulphuric acid in the subsoil, but which the application of gyp- 
sum has introduced into the upper soil. 

The second soil was taken from a field in which sainfoin died regu- 
larly in the second or third year after it was planted. This was naturally 
attributed to something in the subsoil. And by the analyses above 
given, it was found to contain much sulphuric acid in combination with 
oxide of iron, forming sulphate of iron (green vitriol).. This salt being 
noxious to plants, began to act upon the crop of sainfoin as soon as the 
roots had gone so deep as to draw sufficient supplies from the subsoil, 
and it thus gradually poisoned them, so that they died out in two or three 
years. 



EXACT COiVSTFTUENTS OF SOME UNFRUITFUL SOILS. 



287 



n. — BARREN OR UNFRUITFUL SOILS. 

Soils are unfruitful or altogether barren, either when they contain too 
little of one or more of the inorganic constituents of plants, or when some 
substance is present in them in such quantity as to become hurtful or 
poisonous to vegetation. The presence of sulphate of iron in the subsoil 
just described is an illustration of the latter fact. In what way the defi- 
ciency oi ceriam substances really does atiect the agricultural capabilities 
of the soil will appear from the following analyses : — 

1. 2. 3. 4. 

Moor land soil, Another Sanrty Soil on tlie 

near Aurlch, suit from soil from Muschel- 

East Fdesland. tlie same Wetlingen kalic, 

neighbour- in LUne- near Miihl- 
Soil. Subsoil. hood. burg- hausen. 

Silica and auartz Sand . . 70 576—95190 61 57G 96 000 77780 

Alumina 1050— 2 520 0450 500 9 490 

Oxides of Iron 0-252— 1460 0524 2000 5 800 

Oxide of Manganese . . . trace — 0048 trace trace 105 

Lime do.— 336 320 0001 0866 

Magnesia 012— 0125 0130 trace 728 

Potash trace — 0072 trace do. trace 

Soda do. — 01 80 do. do. do. 

Phosphoric Acid ... . do. 0034 do. do. 0003 

Sulphuric Acid do. 0020 do. do. trace 

Carbonic Acid — — — — 0-200 

Chlorine ....... trace — 0015 trace trace trace 

HumicAcid 11910- — 11-470 0200 0732 

Insoluble Bumus .... 16200— — 26530 1299 0-200 

Water _ _ _ _ 4096 

100 100 100 100 100 

Each of these analyses is deserving of aflention. 

1°. That the barrenness of the moor-land soils (1 and 2) is to be at- 
tributed to their deficiency in the numerous substances of which they 
contain only traces, may almost be said to be proved by the fact — one 
long recognised and acknowledged on many of our own moor-lands and 
peaty soils — that when dressed with a covering of the subsoil they be- 
come capable of successful culiivation. The analysis of the subsoil in 
the second column shows that it contains all those mineral constituenLs in 
ivhich the soil itself is deficient — and to the effect of these, therefore, the 
improvement produced upon the soil by bringing it to the surface is alto- 
gether to be attributed. 

2°. The sandy soil. No. 3, is evidently barren for the saine reason as 
the moorland soils, 1 and 2. The soil No. 4 rests on lime-stone, and 
was mixed with 7 percent, of lime-stone gravel, and contains a great 
number of the substances which plants require — but its unfr uiifulness is 
to be ascribed to the want of potash and soda, of sulphuric acid and of 
chlorine. Wood ashes and a mixture of common salt with gypsum or 
sulphate of soda, would probably have remedied these defects. 

3°. Among the fertile soils to which I recently directed yourattention 
(p. 284) was one from Belgium, in which the proportion of organic 
matter was less than half a per cent, of its whole weight. In the above 
table, on the other hand, we have two nearly barren soils, containing 



288 WHAT RENDERS A 5501 L FERTILE. 

eacli 11 per cent, of humic acid, besides a much larger proportion of in- 
soluble organic matter. It is obvious, therefore, that the fertility of a 
soil is not dependent upon its containing this or that proportion of vege- 
table matter, either in a sohible or an insoluble form. It is ceriainly 
true that many very fertile soils do contain a considerable quantity of 
organic matter, in a form in which it may readily yield nourishment to 
the roots of plants. Yet such soils are not fertile merely in consequence 
of the presence of this organic matter, as a source o^ organic food to the 
plant. It may be present, and yet the soils, like those above-mentioned, 
may remain barren. Where soils become fertile apparently by the 
long accumulation of such vegetable matter in the soil, it is not merely 
because of the increase of purely organic substances, such as the humic 
and ulmic acids, but, because, as I have already had occasion to mention 
to you, the decaying vegetable matter which produces them contains 
aiso, and yields to the soil, a considerable abundance of some of those 
inorganic substances which plants necessarily require. The organic 
matter is an indication of their presence in such soils. But they may 
be present without the organic matter. They may either be duly pro- 
portioned in the soil by nature — or they may be artificially mixed with 
it, and then this use of the organic matter may be disf)ensed with. It is 
of more importance to bear this in mind, because not only vegetable 
physiologists, but some zealous chemists also, have laid great stress uj)on 
the quantity of soluble and insoluble organic matter contained in a soil, 
and have been led to consider it as a safe index of the relative fertility 
of different soils. 

The history of science shows, by many examples, that those men 
who adopt extreme views, — who attempt to explain all phenomena of a 
given kind, by reference to a single specific cause — have ever been of 
very great use in the advancement of certain knowledge. Their argu- 
ments, whether well or ill founded, lead to discussion, to further investi- 
gation, to th6 discovery of exceptional cases, and, finally, to the general 
adoption of modified views which recognise the action of each special 
cause in certain special cases, but all in subordination to some more ge- 
neral principle. 

Thus, if some ascribe the fertility of the soil to the presence of the 
alkalies in great abundance, others to that of the phosphates, others to 
that of lime, others to that of alumina, and others, finally, to that of ve- 
getable matter in a soluble state — all these extreme opinions are recon- 
ciled, and their partial truths recognised, in one general principle, that 
a soil to be fertile must contain all the substances which the plant we de- 
sire to grow can only obtain from the soil, and in such abundance as 
readily to supply all its wants ; while at the same time it must contain 
nothing hurtful to vegetable life. 

III. SOILS CAPABLE OF IMPROVEMENT BY THE ADDITION OF 

MINERAL MATTER. 

On the principle above stated depends in very many cases the mode 
of improving soils by the addition of mineral substances, as well as the 
method of explaining the remarkable effects occasionally pcoduced by 
their mixture with the land. The following analyses will place this 
matter in a clearer light : — 



COMPOSITION OF READILY IMPROVEABLE SOILS. 



289 





1. 


2. 


3. 


4. 




Soil near Fa- 


Near Draken- 


Near Ganders- 


Near 




dinghiiftel, on 


bure, on the 


helm, in 


Bruns- 




the Weser. 


Weser. 


Brunswick. 


wick. 


Silica and Quartz Sand 


. 93-720 


92014 


90-221 


95-698 


Alumina . 


. 1-740 


2-652 


2-106 


0-504 


Oxide of Iron . 


. 2-060 


3-192 


3-951 


2-496 


Oxide of Manganese . 


. 0-320 


0-480 


0-960 


trace 


Lime 


. 0-121 


0-243 


0-539 


0-038 


Magnesia . 


. 0-700 


0-700 


0-730 


0-147 


Potash (chiefly in combina- 








tion with Silica) 


. 0-062 


0-125 


0-066 } 


0090 


Soda (do.) 


. 0-109 


0-026 


0-010 s 


V v«y v/ 


Phosphoric Acid 


. 0-103 


078 


0-367 


0-164 


Sulphuric Acid 


. 0-005 


trace 


trace 


0-007 


Chlorine in common Salt 


. 0-050 


trace 


0-010 


0-010 


Humic Acid 


. 0-890 


0-340 


0-900 


0-6-26 


Other Organic matter 


. 0-120 


0-150 


0-140 


0-220 



100 



100 



100 



100 



The first of these soils produces naturally beautiful red clover— -the 
second produces very bad red clover. On comparing the constitution of 
the two soils, we see the second to be deficient in sulphuric acid and 
chlorine. A dressing of gypsum and common salt would supply these 
deficiencies, and render it capable of producing this kind of clover. The 
third soil is remarkable for growing luxuriant crops of pulse, when ma- 
nured with gypsum. The almost total absence of sulphuric acid ex- 
plains this effect. The fourth soil was greatly improved by soap-boiler's 
ash, which supplied it with lime, magnesia, manganese, and other sub- 
stances. 



I need not further multiply examples to show you how much real 
knowledge is to be derived from a rigidly accurate analysis, not only in 
regard to the agricultural capabilities of a soil, but also in regard to the 
natural and necessary food of plants, and to the manner in which 
mineral manures act in promoting and increasing their growth. The 
illustrations I have already presented will satisfy you — 

1°. That a fertile soil must contain all the inorganic constituents which 
the plant requires, and none that are likely to do it an injury. 

2°. That if the addition of a given manure to the soil render it more 
fertile — ^it is because the soil was defective in one or more of those sub- 
stances which the manure contained. 

3°. That if a given application to the land fail to improve it^ — of gyp- 
sum, of bone-dust, of common salt, for example — it is because enough of 
the substance applied is already present, or because something else is 
still wanting to render the previous additions available. 

4°. That the result of extended experience in our country, that the 
clay soils are best for wheat, and sandy soils, such as that of Nor- 
folk, for barley, is not to be considered as anything like a law of nature, 
setting aside the clay land for the special growth of wheat, and denying 



290 PHYSICAL PROPERTIES OP SOILS. 



^ 



to the sandy soils the power of yielding abundant crops of this kind of 
grain. Almost every district can present examples of well cultivated 
fields, where the contrary is proved — and the wheat crops which are 
yearly reaped from the sandy plains of Belgium, demonstrate it on a 
more extended scale. 

Chemically speaking, a soil will produce any crop abundantly, pro- 
vided it contain an ample supply of all that the crop we wish to raise 
may happen to require. But, in practice, soils which do not contain all 
these substances plentifully, are yet found to differ in their power of 
yielding plentiful returns to the husbandman. Such differences arise 
from the climate, the exposure, the colour, the fineness of the particles, 
the lightness or porosity of the soil — from the quantity of moisture it is 
capable of retaining, or from some other of its numerous physical pro- 
perties. These physical properties, therefore, it is necessary shortly to 
consider. 

§ 4. Of the physical properties of soils. 

To the physical properties of soils was formerly ascribed a much 
more fundamental importance than we can now attach to them. Crome 
and Schvibler regarded the fertility of a soil as entirely dependent upon 
its physical properties. Influenced by this opinion, the former published 
the results of an examination of numerous soils in the Prussian provin- 
ces, which are now possessed of no scientific interest; because they 
merely indicate the amount of clay, sand, and vegetable matter which 
these soils severally contained.* The latter completed a very elaborate 
examination of the physical properties of soils, which is very useful and 
instructive ;f but the defective nature of which, in accounting for their 
agricultural capabilities, became evident to the author himself, when the 
more correct and scientific views of Sprengel, illustrated in the preced- 
ing section, afterwards became known to him. In giving, therefore, 
their due weight to the physical properties, we must not forget that in 
nature they are subordinate to the chemical constitution of soils. Plants 
may grow upon a soil, whatever its physical condition — if all the food 
they require be within their reach — while, however favourable the phy- 
sical condition may be, nothing can vegetate in a healthy manner, if the 
soil be deficient in some necessary kind of food, or contain what is. de- 
structive to vegetable life. 

Of the physical properties of soils the most important are their den- 
sity, their power of absorbing and retaining water and air, their capillary 
action, their colour, and their consistence or adhesive power. There 
are one or two others, however, to which it will be necessary shortly to 
advert. 

I. MECHANICAL RELATIONS OF SOILS. 

1°. The density and absolute weight of a soil. — Some soils are much 
heavier than others, not merely in the ordinary sense of heavy and light, 
as denoting clayey and sandy soils, but in reference to the absolute weight 
of equal bulks. 

* Recorded in his Grunds'dtze der Agricultur Chemie. 
t Der Boden und aein verhiiltniss zu den Gewdcftsen. 



ABSOLUTE WEIGHT AND FIRMNESS OT SOILS. 291 

Thus a ?libic foot of dry 

Siliceous or Calcareous Sand— weighs about . 110 lbs. 

Half Sand and half Clay 95 

Of common arable Land, from . . . . 80 to 90 
Of pure agricultural Clay (page 231) ... 75 
Of garden Mould, richer in vegetable matter r 70 
Of a peaty Soil, from 30 to 60 

Sandy soils, therefore, are the heaviest. The weight diminishes with 
the increase of clay, and lessens still further as the quantity of vegetable 
matter augments. 

In practice, the denser a soil is, the less injury will be done to the 
land by the passage of carts and the treading of cattle in the ordinary 
operations of husbandry. In a theoretical point of view it is of conse- 
(juence to vegetation, chiefly in so far as, according to the experiments 
of Schiibler, the denser soils retain their warmth for a longer period when 
the sun goes down, or a cold wind comes on. Thus a peaty soil will 
cool as much in an hour and a half as a pure clay in two, or a sand in 
three hours. 

2°. Of the state of division of the constituent parts of the soil.^- 
With the relative weight of different soils, their state of division is in 
some degree connected. Some soils consist of an admixture of exceed- 
ingly fine particles both of sand and clay — while in others, coarse sand, 
stones and gravels, largely predominate. There can be no doubt that the 
state of the soil in this respect has a material influence upon its produc- 
tive character, and consequently upon its money value, since the labours 
of the husbandman in lands of a stiffer and more coherent nature are 
chiefly expended in bringing them into this more favourable powdery con- 
dition. In the description and examination of a soil, therefore, this pro- 
perty ought by no means to be passed lightly over — since it is one in 
regard to which a mere chemical analysis gives us little or no informa- 
tion. 

In some parts of the country, the farmer diligently gathers the 
stones off' his land, while in others the practice is condemned as hurtful 
to the arable crops. The latter fact is explained by supposing that 
these stones in winter afford shelter to the winter-corn, and in warmer 
seasons protect the ground in some degree from the drying winds, and 
retain beneath them a supply of moisture of which the neighbouring 
roots can readily avail themselves. 

3°. Firmness and adhesive power of soils. — When soils dry in the 
air they cohere and become hard and stiff' in a greater or less degree. 
Pure siliceous sands, alone, do not at all cohere when dry — while pure 
clays become hard and very difficult to pulverize. In proportion to the 
quantity of sand with which the latter are mixed, do their tenacity arid 
hardness diminish. The difficulty of reducing clays to a fine powder in 
the open field, or of bringing them into a good tilth, may be overcome, 
therefore, by an admixture of sand or gravel, hut there are few localities 
where the expense of such an operation does not present an insur- 
mountable obstacle. Thorough draining, however, subsoil ploughing, 
and careful tillage, will gradually bring the most refractory soils of this 
character into a condition in which they can be more perfectly and more 
economically worked. 



jMjn « . ADHESION OF SOILS TO THE PLOUGH. 



n 



Soils also adhere to the plough in different degrees, and, therefore, pre- 
sent a more or less powerful obstruction to its passage. All soils present 
a greater resistance when wet than when dry, and all considerably more 
to a wooden than to an iron plough. A sandy soil when wet offers a re- 
sistance to the passage of agricultural implements, equal to about 4 lbs. 
to the square foot of the surface which passes through it — a fertile vege- 
table soil or rich garden mould about 6 lbs., and a clay from 8 to 25 lbs. 
to the square foot. These differences will naturally form no inconsider- 
able items in the calculations of the intelligent farmer when he estimates 
the cost of working, and the consequent rent he can afford to pay for this 
or that soil, otherwise equal in value. 

II. — RELATIONS OF SOILS TO WATER. 

1*. Power of imbibing moisture from the air. — When a portion of soil 
is dried carefull)'^ over boiling water, or in an oven, and is then spread 
out upon a sheet of paper in the open air, it will gradually drink in watery 
vapour from the atmosphere, and will thus increase in weight. In hot 
climates and in dry seasons this property is of great importance, restoring 
as it does, to the thirsty soil, and bringing within the reach of plants, a 
portion of the moisture which during the day they had so copiously ex- 
haled. 

Different soils possess this property in unequal degrees. During a 
night of 12 hours, and when the air is moist, according to Schiibler, 1000 
lbs. of a perfectly dry 



Clay Loam ... 25 lbs. 
Pure Agricultural Clay 27 



Quartz Sand will gain lbs. 
Calcareous Sand. . 2 
Loamy Soil . . 21 
and peaty soils, or such as are rich in vegetable matter, a still larger 
quantity. 

Sir Humphry Davy found this property to be possessed in the highest 
degree by the most fertile soils. Thus, when made perfectly dry, 1000 
lbs. of a 

Very fertile Soil from East Lothian gained in an hour 18 lbs. 

Very fertile Soil from Somersetshire 16 

Soil worth 45s. per acre from Mersea, in Essex . . 13 

Sandy Soil worth 28s., from Essex 11 

Coarse Sand worth only 15s 8 

Soil of Bagshot Heath 3* 

Fertile soils, therefore, possess this property in a very considerable de- 
gree, and, though we cannot, by determ-ining this property alone, infer 
with safety what the fertility of a soil is likely to prove — since peaty 
soils and very strong clays are still more absorbent of moisture, and 
since this property is only remotely connected with the special chemical 
constitution of a soil — yet among arable, sandy, and loamy lands, it cer- 
tainly does, as Sir Humphry Davy states, afford one means of judging 
of their relative agricultural capabilities. 

2°. Power of containing or holding ivater.—K water be poured dr€>p 
by drop upon a piece of chalk or of pipe-clay, it will sink in and disap- 
pear, but if the dropping be continued, the pores of the earth will by de- 

• Sir H. Davy'a Works, vol. vii., p. 326. 



RELATIONS OF SOILS TO WATKR. 293 

grees become filled with water, and it will at length begin to drop out 
from the under part as it is added above. This property is exhibited in 
a certain degree by all soils. The rain falls and is drunk in, the dew 
also descends, and is thus taken possession of by the soil. But after much 
rain has fallen, the earth becomes saturated, and the rest either runs off 
from the surface or sinks through to the drains. This happens more 
speedily in some soils than in others. Thus from 106 lbs. of dry soil» 
water will begin to drop — if it be a 

Quartz Sand, when it has absorbed 25 lbs. 

Calcareous Sand 29 

Loamy Soil 40 

English Chalk 45— J. 

Clay Loam 50 

Pure Clay 70 

but a dry peaty soil will absorb a very much larger proportion (Schii- 
bler), before it suffers any to escape. Useful arable soils are found to be 
capable of thus containing from 40 to 70percent. of their weight of water. 
If the quantity be less than this, the soils are said to be best adapted for 
pine plantations, — if greater, for laying down to grass. 

In dry climates this power of holding water must render a soil more 
valuable, whereas in climates such as ours, where rains rather over- 
abound, a simple determination of this property will serve to indicate 
to the practical farmer on which of his fields it is most important to him, 
in reference to surface water, that the operation of draining should be 
first and most effectually performed. The more water the soil contains 
within its pores, the more it has to part with by subsequent evaporation ; 
and, therefore, the colder it is likely to be. The presence of this water also 
excludes the air in a great degree, so that for these, as well as for other 
reasons, it is desirable to afford every facility for the speedy removal of 
the excess of water from such soils as absorb it, and are capable of con- 
taining it, in a very large proportion. 

3°. Power of retaining water when exposed to the air. — Unless when 
rain or dew are falling, or when the air is perfectly saturated with mois- 
ture, watery vapour is constantly rising from the surface of the earth. 
The fields, after the heaviest rains and floods, gradually become dry, 
though this, as every farmer has observed, takes place in some of his 
fields with much greater rapidity than in others. Generally speaking, 
those soils which are capable of arresting and containing the largest por- 
tion of the rain that falls, retain it also with the greatest obstinacy, and take 
the longest time to dry. Thus a sand will become as dry in one hour as a 
pure clay in three, or a piece of peat in four hours. This, therefore, not 
only explains, and shows the correctness of, the well-known distinctions 
of warm and cold soils, but exhibits another strong argument in favour 
of a perfect drainage of stiff soils and of such as contain a large proportion 
of decaying vegetable matter. 

4°. Capillary power of the soil. — When water is poured into the sole 
of a flower-pot, the soil gradually sucks it in and becomes moist even to 
the surface. The same takes place in the soil of the open fields. The 
water from beneath — that contained in the subsoil — is gradually sucked 
up to the surface. Where water is present in excess, this capillary action, 
as it is called, keeps the soil always moist and cold. 



294 CAPILLARY POWER OF THE SOIL. 



The tendency of the water to ascend, however, is not the same in all 
soils. In those which, like sandy soils and such as contain much vege- 
table matter, are open and porous, it probably ascends most freely, while 
stiff clays will transmit it with less rapidity. No precise experiments, 
however, have yet been made upon this subject, chiefly, I believe, be- 
cause this property of the soil has not hitherto been considered of such 
importance as it really is, to the general vegetation of the globe. Let us 
attend a little to this point. 

I have already drawn your attention to the fact, that the specimens of 
soil which are submitted to analysis generally contain very little saline 
matter, and yet that in a crop reaped from the same soil a very consider- 
able proportion exists. This I have attributed to the action of the 
rains which dissolve out the soluble saline matter from the surface 
soil, and as they sink, carry it with them into the subsoil; or from 
sloping grounds, and during very heavy rains, partly wash it into the 
brooks. Hence from the proportion of soluble matter present at any one 
time in the surface soil, we cannot safely pronounce as to the quantity 
which the whole soil is capable of yielding to the crop that may be grown 
upon it. For when warm weather comes and the surface soil dries 
rapidly, then by capillary action the wafer rises from beneath, bringing 
with it the soluble substances that exist in the subsoil through which it 
ascends. Successive portions of this water evaporate from the surface, 
leaving their saline matter behind them. And as this ascent and eva- 
poration go on as long as the dry weather continues, the saline matter 
accumulates about the roots of the plants so as to put within their reach 
an ample supply of every soluble substance which is not really defective 
in the soil. I believe that in sandy soils, and generally in all light soils, 
of which the particles are very fine, this capillary action is of great im- 
portance, and is intimately connected with their power of producing 
remunerating crops. They absorb the falling rains with great rapidity, 
and these carry down the soluble matters as they descend — so that when 
the soil becomes soaked, and the water begins to flow over its surface, 
the saline matter being already buried deep, is in little danger of being 
washed away. On the return of dry weather, the water re-ascends from 
beneath and again diffuses the soluble ingredients through the upper soil. 

In climates such as ours, where rains and heavy dews frequently lall, 
and where the soil is seldom exposed for any long period to hot summer 
weather unaccompanied by rain, we rarely see the full effect of ihis ca- 
pillary action of the soil. But in warm climates^ where rain seldom or 
never falls, the ascent of water from beneath, where springs happen to 
exist in the subsoil, goes on without intermission. And as each new 
particle of water that ascends brings with it a particle, however small, 
of saline matter (for such waters are never pure), which it leaves behind 
when it rises into the air in the form of vapour, a crust, at first thin, but 
thickening as time goes on, is gradually formed on the surface of the soil. 
Such crusts are seen in the dry season — in India, in Egypt, and in many 
parts of Africa and America. In hot, protracted summers they may be 
seen on the surface of our own fields, but they disappear again with the 
first rains that fall. Not so where rains are unknown. And thus on the 
arid plains of Peru, and on extensive tracts in Africa, a deposit of saline 
matter, sometimes many feet in thickness, is met with on the surface of 



ii 



ITS IMPORTANCE TO VEGETATION. 296 

wide plains, in the hollows of deep valleys, and on the bottoms of ancient 
lakes. Such an incrustation, probably so formed, is the bed of nitrate of 
soda in Peru, from which all our supplies of that salt are drawn — such 
are the deposits of carbonate of soda (urao) extracted from the soil in the 
South American State of Colombia. 

5°. Contraction of the soil on drying. — Some soils in dry weather di- 
minish very much in bulk, shrink in, and crack. Thus, after being 
soaked by rain, pure clay and peaty soils diminish in bulk about one- 
fifth when they are again made perfectly dry— while sand has the same 
bulk in either state. The more clay or vegetable matter, therefore, a 
soil contains, the more it swells and contracts in alternate wet and dry 
weather. This contraction in stiff clays can scarcely fail to be occa- 
sionally injurious to young roots from the pressure upon the lender fibres 
to which it must give rise, while in light and sandy soils the compres- 
sion of the roots is nearly uniform in all weathers, and they are undis- 
turbed in their natural tendency to throw out off-shoots in every direction. 
Hence another good quality of light soils, and a less obvious benefit 
which must necessarily result from rendering soils less tenacious by ad- 
mixture or otherwise. 

III. RELATIONS OF THE SOIL TO THE ATMOSPHERE. 

Power of absorbing oxygen and other gaseous substances from the 
air. — 1*^. The importance of the oxygen of the atmosphere, first to the 
germination of the seed, and afterwards to the growth of the plant, I have 
already sufficiently insisted upon. It is of consequence, therefore, that 
this oxygen should gain access to every part of the soil, and thus to all 
the roots of the plant. This access can be facilitated by artificially 
working the land, and thus rendering it more porous. But some soils, 
in whatever state they may be in this respect, have been found to absorb 
oxygen with more rapidity, and in larger quantity, than others. Thus 
clays absorb more oxygen than sandy soils, and vegetable moulds or 
peats more than clays. This difference depends in part upon the natural 
porosity of these different soils, and in part also upon the chemical con- 
stitution of each. If the clay contain iron or manganese in the state of 
' first or />ro^oxides, these will naturally absorb oxygen for the purpose of 
combining with it, — while the decaying vegetable matter will in like 
manner, in such as contain it largely, drink in much oxygen to aid their 
natural decomposition. 

2°. Besides the gases, oxygen and nitrogen, of which the air princi- 
pally consists, the soil absorbs also carbonic acid from the atmosphere, 
and portions of those various vapours, — whether of ammonia and other 
effluvia which rise from the earth, or of nitric acid formed in the air,— 
and these, in the opinion of some chemists, contribute very materially to 
its natural fertility. This, however, is very much a matter of conjec- 
ture, and no experiments have been made as to the relative capabilities 
of different soils thus to extract vegetable food from the surrounding air. 
One fact, however, seems to be clearly ascertained, that all soils, namely, 
absorb gaseous substances of every kind most easily and in the greatest 
abundance when they are in a moist state. The fall of rains, or the de- 
scent of dew, therefore, will favour this absorption in dry seasoris, and it 
will also be greatest in those soils which have the power of most readily 



296 POWER OF SOILS TO RETAIN HEAT. 

extracting watery vapour from the air during the absence of the sun. 
Hence the influence of the dews and of gentle showers on the progress 
of vegetation, is not limited to the mere supply of water to the thirsty 
ground, and of those vapours which they bring with them as they descend 
to the earth, but is partly due also to the power which they impart to the 
moistened soil, of .extracting for itself new supplies of gaseous matter 
from the surrounding atmosphere. 

IV. RELATIONS OF THE SOIL TO HEAT. 

There are some of the relations of soils to heat, which have considera- 
ble influence upon their power of promoting vegetation. These are the' 
rapidity with which they absorb heat from the air, the temperature they 
are capable of attaining under the direct action of the sun's rays, and the 
length of time during which they are able to retain this heat. 

1°. Power of absorbing heat. — It is an important fact, in reference to 
the growth of plants, that during sunshine, when the sun's rays beat upon 
it, the earth acquires a much higher temperature than the surrounding 
air- This temperature very often amounts to 110°, and sometimes to 
nearly 150°, while the air in the shade is between 70° and 80° only. 
Thus the roots of plants are supplied with that amount of warmth which 
is most favourable to their rapid growth. 

Dark-coloured — such as black and brownish red — soils absorb the 
heat of the sun most rapidly, and therefore become warm the soonest. 
They also attain a higher temperature — by a few degrees only, how- 
ever (3° to 8°), — than soils of other colours, and thus, under the action 
of the same sun, will more rapidly promote vegetation. In climates, 
such as ours, where the presence of the sun is often wished for in vain 
in time of harvest, this property of the soil possesses a considerable eco- 
nomical value. In other parts of the world, where sunshine abounds, 
it becomes of less importance. 

Every one will understand that the above differences are observed 
among such soils only as are exposed to the same sun under the same 
circumstances. Where the exposure or aspect of the soil is such as to 
give it the prclonged benefit of the sun's rays, or to shelter it from cold 
winds, it will prove more propitious to vegetation than many others less 
favourably situated, though darker in colour and more free from super- 
fluous moisture. 

2°. Power of retaining heat.-— Bui soils differ more in their power of 
retaining the heat they have thus absorbed. You know that all hot bodies, 
when exposed to the air, gradually become cool. So do all soils ; but a 
sandy soil will cool more slowly than a clay, and the latter than a soil 
which is rich in vegetable matter. The difference, according to Schiib- 
ler, is so great, that a peat}'' soil cools as much in one hour as the same 
bulk of clay in two, or of sand in three hours. This may no doubt have 
considerable influence upon growing crops, inasmuch as, after the sun 
goes down, the sandy soil will be three hours in cooling, while the clays 
will cool to the same temperature in two, and rich vegetable mould in 
one hour. But on those soils which cool the soonest, dew will first begin 
to be deposited, and it is doubtful, where the soils are equally drained, 
whether, in summer weather, the greater proportion of dew deposited on 
the clays and vegetable moulds may not more than compensate to the 



POWER OF MODlFriNG THE PHYSICAL CHARACTERS. 297 

parched soil — for the less prolonged duration of the elevated tempera- 
ture derived from the action of the sun's rays. It is also to be remem- 
bered, that vegetable soils at least absorb the sun's heat more rapidly 
than the lighter coloured sandy soils, and thus the plants which grow in 
the former, which is sooner heated, may in reality be exposed to the 
highest influence of the sun's warmth— for at least as long a period as 
those which are planted in the latter. 

The only power we possess over these relations of soils to heat, ap- 
pears to be, that by top-dressing with charcoal, with soot, or with dark- 
coloured composts, we may render it more capable of rapidly absorbing 
the sun's heat, and by admixture with sand, more capable of retaining 
the heat which it has thus obtained. 



Sucn are the most important of the physical properties of soils. Over 
some of them, the skilful farmer possesses a ready control. He can 
drain his land, and thus render it cheaper to work and more easy to re- 
duce to a fine powder. He can plough, subsoil, and otherwise work it 
well, and thus can make it more open and porous, more accessible both 
to air and water. When it is light and peaty, he can lay heavy matter 
over it — clay, and sand, and lime-stone rubble — and can thus increase 
its density. He can darken its colour in some localities with peat com- 
posts, and can thus make it more absorbent of heat and moisture, as well 
as more retentive of the rain that falls. But here his power ends, and 
how far any of the changes within his power can be 'prudently attempted 
will depend upon the expense which, in any given locality, the operation 
would involve. And even after he has done all which mere mechanical 
skill can suggest, the soil may still disappoint his hopes, and refuse to 
yield him remunerating crops of corn. 

" A soil," says Sprengel, " is often neither too heavy nor too light, 
neither too wet nor too dry, neither too cold nor too warm, neither too 
fine nor too coarse; — lies neither too high nor too low, is situated in a 
propitious climate, is found to consist of a well-proportioned mixture of 
clayey and sandy particles, contains an average quantity of vegetable 
matter, and has the benefit of a warm aspect and favouring slope." — 
[BodenJcunde, p. 203.] It has all the advantages, in short, which 
physical condition and climate can give it, and yet it is unproductive. 
And why ? Because, answers chemical analysis, it is destitute of cer- 
tain mineral constituents which plants require for their daily food. The 
physical properties, therefore, are only accessory to the chemical consti- 
tution. They bring into favourable circumstances, and thus give free 
scope to the operation, upon the seeds and roots of plants, of those che- 
mical substances which Nature has kindly placed in most of our soils, or 
by the lessons of daily experience is teaching the skilful labourer in her 
fields to supply by art. 

And yet the study of the physical properties of soils is not without its 
use, even in a theoretical point of view. It shows both the use of the 
fundamental admixture of sand, clay, and vegetable matter, of which 
our soils consist, and for what special end all the mechanical labours of 
the husbandman are undertaken, and why thev are so necessarv. Plants 



298 GENERAL FUNCTIONS OK THE SOIL. 

must be firmly fixed, therefore the soil must have a certain consistency, 
— their roots must find a ready passage in every direction ; therefore the 
soils must be somewhat loose and open. Except for these purposes, we 
see little immediate use for the sand and alumina which form so much 
of the substance of soils — till we come to study iheir physical properties. 
The siliceous sand is insoluble,* and the alumina exists in plants in very 
minute quantity only, while during the progress of natural vegetation, 
the proportion of vegetable matter in the soil actually increases. The 
immediate agency, tlierefore, of these substances is not chemical but 
physical. 

The alumina oftlie clays is of immediate use in absorbing and retain- 
ing both water and air for the use of the roots— while the vegetable mat- 
ter is advantageous in reference to the same ends, as well as to the power 
of absorbing quickly and largely the warmtii of the sun's rays. The 
soil, in short, in reference to vegetation, performs the four following dis- 
tinct and separate, but each of them important and necessary, func- 
tions : — 

1°. It upholds and sustains the plant, affording it a sure and safe an- 
chorage. 

2°. It absorbs water, air, and heat, to promote its growth 

These are its mechanical and physical functions. 

3°. It contains and supplies to the plaiU both organic and inorganic 
food as its wants require ; and 

4°. It is a workshop in which, by the aid of air and moisture, chemi- 
cal changes are continually going on ; by which changes these several 
kinds of food are prepared for admission into the living roots. 

These are its chemical functions. 

All the operations of the husbandman are intended to aid the soil in the 
performance of one or other of these functions. To the most important 
of lliese operations — the methods adopted by the practical farmer for 
improving the«oil — it is my intention, in the following division of these 
Lectures, briefly to direct your attention. 



LECTURES 

ON THE 

APPLICATIONS OF CHEMISTRY AND GEOLOGY 

TO 

AGRICULTURE. 



ON THE IMPROVEMENT OF THE SOIL BY ME- 
CHANICAL AND CHEMICAL MEANS. 



CONTENTS OF PART III. 



LECTURE XIV. 

THE aUALITIES OF THE SOIL MAY BE CHANGED BY ART. 

Connection between the kind of soil and I Oft lie tlieory of springs p. Sf2 

tiie kind of plants that grow upon it., p. 304 | Of ploughing and subsoiling 318 

Of draining, and its effects 306 1 Of deep-plougliinff and trenciiing 32i 

Practical effects of draining 311 | Improvement of liie soil by mixing 323 



LECTURE XV. 

IMPROVEMENT OF THE SOIL BY CHEMICAL MEANS. 



Of saline manures .357 

Theory of the action of potash and soda.. 328 
Sulphates of potash, soda, magnesia, and 

lime (gypsum) . . 331 

Theory ofihe action of these sulphates. .332 

Niirates of potash and soda 335 

Effect of these niirates on the quantity of 

various crops 336 

Effect of die nitrates on the quality of 

the crop 3-39 

Cases inwhi.h they have failed 341 

Theory of the action of these nitrates 343 

Special effects of the nitrates of potash 

and soda 344 



Use of common salt 34& 

Cldoriiip.sof calcium and magnesium... 347 
Phosphate of lin e nnd earth of bones.. . .343 

Sili( ales of potash and soda 349 

Sails of aninionia ib. 

Ofn-.ixcfl saline manures 352 

Wood ashes ib. 

TTse of kelp 355 

S raw ashes .35^5 

TurfpPHt or Dulchashes 3.'59 

Crushed gri\niips and lavas 361 

Results of experiments with mixed ma- 
nures 362 



LECTURE XVI. 

OF THE USE OF LIME AS A MANURE. 



Of the composition of common and mag- 
nesian lime-stones 364 

Of the burning and slaking of lime 360 

Changes which the hydrates of lime and 
magnesia undergo by j)rolonged expo- 
sure to the air 367 

States of chemical eombination in which 
lime may be applied to the land 369 

Of the various natural forms in wliich 
ca;'/^ona/eoflime is applied to the land. .370 

Effects of marl, and of the coral, shell, 
and lime-stom- sands u|ium the soil . . . .374 

Of the use of chalk as a manure 375 

Is lime indispensable to the fertility of 
thesoin 377 

States of ••ombination in which lime ex- 
ists in the soil . 379 

Of the (luaniity of lime which ought to 
be added lo ihe soil 381 

Ouuhi lime to be apjilied in larse doses 
at distant intervals, or in smaller quan- 
tities more fn-queiitly repeateil I 383 

Form and slate ol cumhinaiion in which 
liBif ouiihl to be applied to the land. . . 3S6 

Tiseand advantage ol the compost form.. 388 

When oiinht lime to be applii-d 1 :^89 

Of the effects produced t>y lime upon the 
land and upon The crops 39U 

Circumstances by which the effects of 
lime are modified .393 

Effects of an overdose of lime 395 



Length of time during which lime acts. . . .396 

Of the sinking of lime into the soil 397 

Why liming must h<; repeated 398 

Theory of the action of lime 400 

Of lime as Ihe food of plants ib. 

The tiiemical action of lime is exerted 
diifjly on the organic matter of the 
soil 401 

Of ihe forms in which organic matter 
usualh exisLs in the soil, and the cir- 
cumstances under which its decompo- 
siiiiin may take place lb. 

General action of alkaline substances 
upon organic matter 403 

Special efft- cts of caustic lime upon the 
several varieiies of organic matter in 
the soil 404 

Action of niild (or carbonate of) lime 
upon the vpiretable matter of ihe soil. . .406 

Of the comparaiive utility of burned and 
unburned lime .408 

Action of lime on organic substances 
which contain iiiiroi'en 409 

How these chemical changes directly 
benefit vegetation 412 

Why lime must be kept near the surface.. ib. 

Action of lime U|)on the inorganic or 
mineral matter ot the soil 413 

Aition of lime on animal and vegetable 
life 415 

Use of silicate of lime., 416 



vin 



CONTENTS OP PART III. 



LECTURE XVII. 

OF OUGANIC MANURES. 



Of green manuring^or the application of 
vegetable matter in a green state. . . .p. 417 

Important practical results obtained by 
green manuring 418 

Of the plants which in different soils and 
climates are employed for green ma- 
nuring 419 

Will green manuring alone prevent land 
from becoming exhausted 7 421 

Of the practice of green manuring 422 

Of natural manuring with recent vegeta- 
ble matter ib. 

"Weight of roots left in the soil by the dif- 
ferent grasses and clovers 423 



Improvement of the soil by laying down 
to grass p. 424 

Improvement of the soil by the planting 
of trees 429 

Of the use of sea- weed as a manure 431 

Of manuring with dry vegetable sub- 
stances 433 

Use of rape-dust 434 I ] 

Use of decayed vegetable matter as a 
manure 436 

Use of chaned vegetable matters — soot, 
&c., as manures ....437 

Of the theoretical value of different ve- 
getable substances as manures 440 j 



LECTURE XVin. 

ANIMAL MANURES. 



Of flesh, blood, and skin 443 

Of wool, woollen rags, hair, and horn. . . .445 

Of the composition of bones 446 

On what does the fertilizing action of 

bones depend? 447 

Of the application of bone-dust to pasture 

lands 451 

Of animal charcoal, the refuse of the su- 
gar refineries, and animalized carbon.. 452 
Offish, fish refuse, whale blubber, and 

oil. 453 

Relative fertilizing value of the animal 

manures already described 454 

Of the droppings of fowls — pigeons' dung 

and guano 456 

Results of experiments with guano 459 

Of liquid animal manures — the urine of 
man, of the cow, the horse, the sheep, 

and the pig 460 

Of the waste of liquid manure — of urate 
and of sulphaled urine 463' 



Of solid animal manures — night soil, the 
dung of the cow, the horse, the sheep, 
and the pig 465 

Of the quantity of manure produced 
from the same kind of food by the 
horse, the cow, and the sheep 468 

Of ihe relative fertilizing values of differ- 
ent animal excretions 469 

Influence of circumstances on the quali- 
ty of animal manures 470 

Of the changes which Ihe food under- 
goes in passing through the bodies of 
animals 472 

Of farmyard manure, and the loss it un- 
dergoes by fermenting 474 

Of top-dressing with fermenting ma- 
nures 477 

Of eating off with sheep 478 

Of the improvement of the soil by irriga- 
tion ....479 



EBRATxnB, p. 364.— Lecture XVI. is erroneously printed XVIL 



LECTURE XIV. 

The physical qualities and chemical constitution of a soil may be changed by art.— Nature 
of the plants dependent upon that of the soil on which they grow. — Mechanical methods 
of improving the soil. — Effects produced by di'aining. — Tlieory of springs. — Elfect of 
ploughing, subsoiling, deep ploughing and trenching. — Artificial improvement by mixing 
with clay, sand, or marl. 

The facts detailed in the preceding lecture may be considered as af- 
fording sufficient proof that the ability of the farmer to grow this or that 
crop upon his land, is very much restrained by its natural character and 
constitution. Each soil establishes upon itself — so to speak — a vegeta- 
tion suited to its own nature, one that requires most abundantly those 
substances which actually abound in the soil — and the art of man can- 
not long change this natural connection between the living plant and the 
kind of land in which it delights to grow. 

But he can change the character of the land itself. He can alter 
both its physical qualities and its chemical constitution, and thus can fit 
it for growing other races of plants than those it naturally bears — or, if he 
choose, the same races in greater abundance, and with increased luxuri- 
ance. It is, in fact, in the production of such changes, that nearly all the 
labour and practical skill of the husbandman — apart from local peculiari- 
ties of climate, &c. — is constantly expended. For the attainment of 
this end he drains, ploughs, subsoil-ploughs, and otherwise works his 
land. For this end he clays, sands, marls, and manures it. By these 
and similar operations the land is so changed as to become both able and 
willing to nourish and ripen those peculiar plants which the agriculturist 
wishes to raise. On this practical department of the art of culture, 
the principles explained and illustrated in the preceding parts of these 
lectures, throw much light. They not only explain the reason why cer- 
tain practices always succeed in the hands of the intelligent farmer — but 
why others also occasionally and inevitably fail — they tell him which 
practices of his neighbours he ought to adopt, and which of them he had 
better modify or wholly reject, — and they direct him to such new modes 
of improving his land as are likely to add the most to its permanent 
productive value. 

The operations of the husbandman in producing changes upon the 
land, are either mechanical or chemical. • When he drains, ploughs, 
and subsoils, he alters chiefly the physical characters of his soil — when 
he limes and manures it, he alters its chemical constitution. These two 
classes of operations, therefore, are perfectly distinct. Where a soil eon- 
tains all that the crops we desire to grow are likely to require, mere me- 
chanical operations may suffice to render it fertile — but where one or 
more of the inorganic constituents of plants are wanting, draining may 
prepare the land to benefit by further operations, but it will not be alone 
sutficient to remove its comparative sterility. I shall, therefore, con- 
sider in succession these two classes of practical operations : — 

1°. Mechanical methods of improving the soil, including draining, 
ploughing, mixing with clay, sand, &c. 
26 



}04 PLANTS PECULIAR TO CERTAIN SOILS. 



"■ 



2°. Chemical methods, including limeing, marling, and ihe application 
of vegetable, animal, and mineral manures. 

Tosatisfy you fully, however, in regard to the absolute necessity 
for such changes, if we would render the land fit to produce any given 
crop, let me illustrate, by a few brief examples, the intimate relation 
observed in nature between the kind of soil and the kind of plants that 
grow upon it. 

§ 1. On the connection between the hind of soil and the hind of plants 

that grow upon it. 

That a general connection exists between the kind of soil and the 
kind of plants that grow upon it, is familiar to all practical men. Thus 
clay soils are generally acknowledged to be best adapted for wheat — 
loamy soils for barley — sandy loams for oats or barley — such as are more 
sandy still for oats or rye — and those which are almost pure sand, for 
rye alone of all the corn-bearing crops. 

But in a state of nature, we find special differences among the spon- 
taneous produce of the soil, which are more or less readily traceable to 
its chemical constitution in the spots where the plants are seen to 
grow. Thus — 

1°. On the sandy soils of the sea shores, and on the salt steppes of 
Hungary and Russia, the sand-worts, salt-worts, glass- worts, and other 
salt-loving plants abound. When these sands are inclosed and drained, 
the excess of the salt is gradually washed out by the rains, or in some 
countries is removed by reaping the saline plants annually, and burning 
them for soda (barilla), when wholesome and nutritive grasses take their 
place ; but the white clover and the daisy, and the dandelion, must first 
appear, before, as a general rule, it can be profitably ploughed up and 
sown with corn. 

2°. The dry drifted sands, more or less remote from the sea, produce 
no such plants. They are distinguished by their own coarse grasses, 
among which the elymus arenarius (upright sea lyme-grass) often, in our 
latitudes, occupies a conspicuous place. On the downs of North Jut- 
land, it was formerly almost the only plant which the traveller could 
meet with over an area of many miles. 

3°. On ordinary sandy soils leguminous plants are rare, and the her- 
bage often scanty and void of nourishment. With the presence of marl 
in such soils, the natural growth of leguminous plants increases. The 
colt's-foot also, and the butter-bur, not only grow naturally where the 
subsoil is marly, but infest \X. sometimes to such a degree as to be with 
great difficulty extirpated. So true is this indication of the nature of 
the soil, that in ihe lower vallies of Switzerland these plants are said to 
indicate to the natives where they may successfully dig for marl.* On 
calcareous soils, again, or such as abound in lime, the quicken or couch- 
grass is seldom seen as a weed, f while the poppy, the vetch, and the 
darnel abound. 

4°. So peaty soils, when laid down to grass, slowly select for them- 

* Prize Essays of the Highland Society, I , p. 134. 
t Sprengelj Bodenkunde^ p. 201, 



NATURAL ROTATION AMONG FOREST TREES. 305 

selves a peculiar tribe of grasses, especially suited to their own nature, 
among which the liolcus Icmatus (meadow soft-grass) is remarkably 
abundant. Alter their constitution by heavy limeing, and they produce 
luxuriant green crops and a great bulk of straw, but give a coarse thick- 
skinned grain, more or less imperfectly filled. Alter them further by a 
dressing of clay, or keep them in arable culture, and stiffen them with 
composts, and they will be converted into rich and sound corn-bearing 
lands. 

5°. In the waters that gush from the sides of lime-stone hills — on the 
bottoms of ditches that are formed of lime-stones or marls — and in the 
springs that have their rise in many trap rocks, the water-cress appears 
and accompanies the running waters, sometimes for miles on their 
course. The mare's-tail {equiseMm), on the other hand, attains its largest 
size by the marshy banks of rivulets in which not lime but silica is 
more abundantly present. So the Cornish heath {erica vagans) is found 
only over the serpentine soils of Cornwall, and the red broom rape 
{orobanche rubra)* only on decayed traps in Scotland and Ireland. 

These facts all point to the same natural law, that where other circum- 
stances of climate, moisture, &c., are equal, the natural vegetation — that 
which grows best on a given sjJot — is entirely dependent upon the chemical 
constitution of the soil. 

But both the soil, and the vegetation it willingly nourishes, are seen 
to undergo slow but natural changes. Lay down a piece of land to grass, 
and, after a lapse of years, the surface soil — originally, perhaps, of the 
stifFest clay — is found to have become a rich, light, vegetable mould, 
bearing a thick sward of nourishing grasses, almost totally different 
from those which naturally grew upon it when first converted into pas- 
ture. So in a wider field, and on a larger scale, the same slow changes 
are exhibited in the vast natural forests that are known to have long 
covered extensive tracts in various countries of Europe. 

Thus it is a matter of history that Charlemagne hunted in the forest 
of Gerardmer, then consisting of oak and beech — though now the same 
forest contains only pines of various species. On the Rhine, between 
Landau and Kaiserlautern, oak forests, of several centuries old, are seen 
to be gradually. giving way to the beech, while others of oak and beech are 
yielding to the encroachments of the pine. In the Palatinate, the 
Scotch fir {pinus sylvestrls) is also succeeding to the oak. In the Jura, 
and in the Tyrol, the beech and the pine are seen mutually to replace 
each other — and the same is seen in many other districts. When the 
time for a change of crop arrives, the existing trees begin to languish 
one after another, their branches die, and finally their dry and naked 
tops are seen surrounded by the luxuriant foliage of other races.f These 
facts not only show how much the vegetable tribes are dependent upon 
the chemical nature of the soil — they indicate, likewise, the existence 
of slow natural changes in the constitution of the soil, which lead neces- 
sarily to a change of vegetation also. 

We can ourselves, in the case of ancient forests, effect such changes. 
When in the United States a forest of oak or maple is cut down, one of 

• Hooker's Flora Scotica. 

t Le Baron de Mortemart de Boisse, Voyage dans les Landes, p. 189. 



306 OF DRAINING, AND ITS EFFECTS. 

pine springs up in Its place ; while on the site of a pine forest, oak and 
other broad-leaved trees speedily appear. 

But if the full time for such changes has not yet come, the new vege- 
tation may be overtaken, and smothered by the original tribes. Thus, 
when the pine forests of Sweden are burned down, a young growth of 
birch succeeds, but after a time the pines again appear and usurp their 
former dominion. The soil reniains, still, more propitious to the growth 
of the latter than of the former kind of tree. 

We may, therefore, take a practical lesson from the book of nature. 
If we wish to have a luxuriant vegetation upon a given spot, we must 
either select such kinds of seeds to sow upon it as are fitted to the kind 
of soil, or we must change the nature of the land so as to adapt it to our 
crop. And, even when we have once prepared it to yield abundant re- 
turns of a particular kind, the changes we have produced can only be 
more or less of a temporary nature. Our care and attention must still 
be bestowed upon it, that it may be enabled to resist the slow natural 
causes of alteration, by which it is gradually unfitted to nourish those 
vegetable tribes which it appears now to delight in maintaining. 

Let us now turn our attention, therefore, to the methods by which 
these beneficial changes are to be effected and maintained. 

^ 2. Of draining, and its effects. 

Among the merely mechanical methods by which those changes are 
to be produced upon the soil, that are to fit it for the better growth of 
valuable crops, draining is now allowed to hold the first place. That it is 
an important step in heavy clay lands, and that it must be the first step 
in all cases where water abounds in the surface soil, will be readily con- 
ceded ; but that it can be beneficial also in situations where the soils are 
of a sandy nature — where the subsoil is light and porous — or where the 
inclination of the field appears sufficient to allow a ready escape to the 
water, does not appear so evident, and is not unfrequently, therefore, a 
matter of considerable doubt and difficulty. It may be useful, then, 
|)riefly to state the several effects which in different localities are likely to 
follow an efficient drainage of the land : — 

1°. It carries off' all stagnant water, and gives a ready escape to the 
excess of what falls in rain. 

2°. It arrests the ascent of water from beneath, whether by capillary 
action or by the force of springs — and thus not only preserves the sur- 
face soil from undue moisture, but also frees the subsoil from the lingering 
presence of those noxious substances, which in undrained land so fre- 
quently lodge in it and impair the growth of deep-rooted plants. 

3°. It allows the water of the rains, instead of merely running over 
and often injuriously washing the surface, to make its way easily through 
the soil. And thus, while filtering through, not only does the rain-wa- 
ter impart to the soil those substances useful to vegetation, which, as 
we have seen,* it always contains in greater or less abundance; but 
it washes out of the upper soil, and, when the drains are deep enough, 
out of the subsoil also, such noxious substances as naturally collect and 
may have been long accumulating there — rendering it unsound and 

* See Lecture II., § 6 ; Lecture IV., § 6 ; and Lecture VIIL, § 5. 



SECURES A DRY SEED-TIME AND AN EARLY HARVEST. 307 

hurtful to the roots. The latter is one of those benefits which gradually 
follow the draining of land. When once thoroughly effected, it consti- 
tutes a most important permanent improvement, and one which can be 
fully produced by no other available means. It will be permanent, 
however, only so long as the drains are kept in good condition. The 
same openness of the soil which enables the rains to wash out those solu- 
ble noxious substances, which have been long collecting, permits them 
to carry off also such as are gradually formed, and thus to keep it in a 
sound and healthy state ; but let this openness be more or less impaired 
by a neglect of the drainage, and the original slate of the land will again 
gradually return. 

4^. This constant descent of water through the soil causes a similar 
constant descent of fresh air through its pores, from the surface to the depth 
of the drains. When the rain falls, it enters the soil and more or less com- 
pletely displaces the air which is contained within its pores. This air 
either descends to the drains or rises into the atmosphere. When the 
rain ceases, the water, as it sinks, again leaves the pores of the upper 
soil open, and fresh air consequently follows. It is in fact sucked in 
after the water, as the latter gradually passes down to the drains. Thus, 
where a good drainage exists, not only is the land refreshed by every 
shower that falls — not only does it derive from the rains those important 
substances which occasionally, at least, are brought down by them from 
the atmosphere, and which are in a great measure lost where the waters 
must flow over the surface — but it is supplied also with renewed acces- 
sions of fresh air, which experience has shown to be so valuable in pro- 
moting the healthy growth of all our cultivated crops- 

5°. But other consequences of great practical importance follow from 
these immediate effects. When thus readily freed from the constant 
presence of water, the soil gradually becomes drier, sweeter, looser, and 
more friable. The hard lumps of the stiff clay lands more or less dis- 
appear. They crumble more freely, offer less resistance to the plough, 
and are in consequence more easily and economically worked. These 
are practical benefits, equivalent to a change of soil, which only the 
farmer of stubborn clays can adequately appreciate. 

6°. With the permanent state of moisture, the coldness of many soils 
also rapidly disappears. The backwardness of the crops in spring, and 
the lateness of the harvests in autumn, are less frequently complained 
of — for the drainage in many localities produces effects which are equi- 
valent to a change of climate. " In consequence of the drainage which 
has taken place in the parish of Peterhead, in Aberdeenshire, during,the 
last 20 years, the crops arrive at maturity ten or fourteen days sooner 
than they formerly did ;"* and the same is true to a still greater extent 
in many other localities. 

7°. On stiff clay lands, well adapted for wheat, wet weather in au- 
tumn not unfrequently retards the sowing of winter corn — in undrained 
lands, often completely prevents it — compelling the farmer to change his 
system of cropping, and to sow some other grain, if the weather permit 
him, when the spring comes round. An efficient drainage carries off the 

* Mr. Gray, in the Prize Essays of the Highland and Agricultural Society ,\\., p. 171. This 
opinion was given in 1830, since which time many other extensive improvements have been 
made in that part of the island. 
26* 



308 IS EQUIVALEPfT TO A DEEPENING OF THE SOIL* 



the i' 



water so rapidly as to bring the land into a workable state soon after the 
rain has ceased, and thus, to a certain extent, it rescues the farmer from 
the fickle dominion of the uncertain seasons.* To the skilful and in- 
telligent farmer, who applies every available means to the successful 
prosecution of his art, the promise even in our age and country is sure 
— " that seed-time and harvest shall never fail." 

8°. But on lands of every kind this removal of the superfluous water 
is productive of another practical benefit. In its consequences it is equi- 
valent to an actual deepening of the soil. 

When land, on which the surface water is in the habit of resting, be- 
comes dry enough to admit the labours of the husbandman, it is still 
found to be wet beneath, and the waters, even in dry seasons, not unfre- 
quently remain where the roots of the crops would otherwise be inclined 
to come. Or, if the surface soil permit a ready passage to the rains, and 
waters linger only in the moist subsoil, still — though the farmer may 
not be delayed in his labours — the subsoil repels the approach of the 
roots of his grain, and compels them to seek their nourishment from the 
surface soil only. But remove the waters, and the soil becomes dry to 
a greater depth. The air penetrates and diffuses itself wherever the 
waters have been. The roots now freely and safely descend into the 
almost virgin soil beneath. And not only have they a larger space 
through whicli to send their fibres in search of food, but in this hitherto 
ungenial soil they find a store of substances — ^but sparingly present, it may 
be, in the soil above — which the long-continued washing of the rains, 
or the demands of frequent crops, may have removed, but which may 
have been all the time accumulating in the subsoil, into which the 
roots of cultivated plants could rarely with safety descend. It is not 
wonderful, then, that the economical effects of draining should be found 
by practical men to be not only a diminution in the cost of cultivation, but 
a considerably augmented produce also both in corn and grass; or that 
this increased produce should alone be found sufficient to repay the en- 
tire cost of thorough-draining in two or three years. 

An obvious practical suggestion arises out of the knowledge of this 
fact. The deeper the drains, provided the water have still a ready es- 
caj)e, the greater the depth of soil which is rendered available for the 
purposes of vegetable nutrition. Deep-rooted plants, such as lucerne, 
often fail, even in moderately deep soils, because an excess of water or 
the presence of some noxious ingredient which deep drains would re- 
move, prevents their natural descent in search of food. Even plants, 
which, like that of wheat or clover, do not usually send down their roots 
so far, will yet, where the subsoil is sound and dry, extend their fibres for 
three or more feet in depth, in quest of more abundant nourishment. 

Not only, then, do deep drains permit the use of the subsoil plough 
without the chance of injury, — not only are they less liable to be choked 
up by the^acumulated roots of plants which naturally make their way 

* "Formerly," says Mr. Wilson, of Cumledge, in his account of the drainage of a farm 
in IJerwickshire, " this part of the farm was so wet, that — though better adapted for wheat 
than any other crop — the season for sowing was frequently lost, and after an expensive fal- 
lowing and limeing, it was sown with oats in spinrg of which it always produced very poor 
crops. It is now so dry as to giow very good crops of turnip or rape, and exxept in two 
intances, I have always sown my wheat in capital order." — Frize Essays of the Highland 
and Agriultural Societt/, I., p 243. 



EFFECT OF A GENERAL DRAINAGE OF THE SOIL. 309 

into them in search of water, — but they also increase the value and per- 
manent fertility of the land, by increasing its available depth. In other 
words, that kind of drainage which is most efficiently performed, with a 
regard to the greatest number of contingencies, will not only be the most 
permanent, but will also be followed by the greatest number of economi- 
cal advantages. 

9°. Nor do the immediate and practical benefits of draining end with 
the attainment of these beneficial results. It is not till the land is ren- 
dered dry that the skilful and enterprising farmer has a fair field on 
which to expend his exertions. In wet soils, bones, wood -ashes, rape- 
dust, nitrate of soda, and other artificial manures, are almost thrown 
away. Even lime exhibits but one-half of its fertilizing virtue, where 
water is allowed to stagnate in the soil. Give him dry fields to work 
upon, and the well-instructed agriculturist can bring all the resources, 
as well of niodern science as of old experience, to bear upon them, with 
a fair chance of success. The disappointments which the holder of un- 
drained lands so often meets with, he will less frequently experience. 
An adequate return will generally be obtained for his expenditure in 
manuring and otherwise improving his soil, and he will thus be encour- 
aged to proceed in devoting his capital to the permanent amelioration of 
his farm — not less for his own than for his landlord's benefit. 

Viewed in this light, draining is only the first of a long series of im- 
provements, or rather it is a necessary preparative to the numerous im- 
provements of which the soil of islands is susceptible — which improve- 
ments it would be a waste of money to attempt, until an efficient system 
of drainage is established. And when we consider how great a national 
benefit this mere preparatory measure alone is fitted directly to confer 
upon the country, you will agree with me in thinking that every good 
citizen ought to exercise his influence in endeavouring, in his own district, 
more or less rapidly to promote it. It has been calculated that the drain- 
age of those lands only, which are at present in arable culture (10 rail- 
lions of acres), would at once increase their produce by 10 millions of 
quarters of the various kinds of grain now grown upon them ; — and that 
a similar drainage of the uncultivated lands (15 millions of acres) 
would yield a furtlier increased produce of twice as much more. This 
increase of 30 millions of quarters is equal to nearly one-half of our pre- 
sent consumption* oi all kinds of grain — so that were it possible to effect 
at once this general drainage, a large superfluity of corn would be raised 
from the British soil. 

This general drainage, however, cannot possibly be effected in any 
given time. The individual resources of the land-owners are not suffi- 
cient to meet the expense, f and such calculations as the above are use- 
ful, mainly, in stimulating the exertions of those who have capital to 
spare, or such an excess of income as can permit them to invest an an- 
nual portion permanently^ in the soil. 

* 65 millions of quarters. See an excellent paper on this subject in the Quarterly Agri- 
cultural Journal, xii., p. 505, by Mr. Dudgeon, of Spyelaw, in Roxburghshire, a county in 
which thepractical benefits of draining have been extensively experienced, and are therefore 
well understood. 

t To drain 25 millions of acres, at jG6 an acre, would cost 150|millions sterling, a sum equal, 
probably, to the whole capital at present invested m farming the land. 

X By an efficient drainage the soil is permanenlli/ benefitted^ but it is not so clear that the 



310 RENDERS A COU^JTRY MORE SALUBRIOUS. 

]0^. He who drains and thus improves his own land, confers a 
benefit upon his neighbours also. In the vicinity of wet and boggy 
lands the hopes of the industrious farmer are often disappointed. Mists || 
are frequent and rains more abundant on the edges of the moor, and 
mill-dews retard the maturity, and often seriously injure the crops. Of 
undrained land, in general, the same is true to a less extent, and 
the presence of one unimproved property in the centre of an enterpris- 
ing district, may long withhold from the adjoining farms that full mea- 
sure of benefit which the money and skill expended upon them would 
in other circumstances have immediately secured. 

So true is it in regard to every new exercise of human skill and in 
every walk of life, that we are all mutually dependent, every one upon 
every other ; and that the kindly co-operation of all can alone secure 
that ample return of good, which the culture either of the dead earth 
or of the living intellect appears willing, and we may hope is ultimately 
destined, to confer upon our entire race. 

11°. I would not here willingly neglect to call your attention to a 
higher benefit still, which the skilful drainage of an extensive district is 
fitted to confer upon its whole population. Not only is this drainage 
equivalent, as above stated, to a change of climate in reference to the 
growth and ripening of plants, but it is so also in reference to the gene- 
neral health of the people, and to the number and kind of the diseases 
to which they are observed to be exposed. 

I may quote in illustration of this fact the interesting observations of 
Dr. Wilson on the comparative state of health of the labouring popula- 
tion in the district of Kelso during the last two periods of ten years. In 
his excellent paper on this subject, in the Quarterly Journal of Agricul- 
ture,* he has shown that fever and ague, which formed nearly one-half 
of all the diseases of the population during the former ten years, have 
almost wholly disappeared during the latter ten, in consequence of the 
general extension of an eflfiicient drainage throughout the country ; while, 
at the same time, the fatality of disease, or the comparative number of 
deaths from every hundred cases of serious ailment, has diminished in 
proportion of 4*6 to 2*59. Such beneficial results, though not immedi- 
ately sought for by the practical farmer, yet are the inevitable conse- 
quence of his successful exertions. Apart, therefore, from mere con- 
siderations of pecuniary profit, a desire to promote the general comfort 
and happiness of the entire inhabitants of a district may fairly influ- 
ence tiie possessors of land to promote this method of ameliorating the 
soil ; while the whole people, on the other hand, of whatever class, 
ought " gratefully to acknowledge the value of those improvements 
which at once render our homes more salubrious and our fields more 
fruitful." 



money it costs is permanently invested or buried in the soil. If the cost be repaid by the 
increase of produce, in three years, the money is not invested, it is only lent for this period 
to the soil. "I drain so many acres every year," said the holder of a large Berwickshire 
farm to me, "and I find myself" always repaid by the end of the third season. If I have 
spare capital enough, therefore, to go on for three years, I can gradually drain any extent of 
land, by the repeated use of the same sum of money." 

' Volume xii., p. 317. 



BENEFITS POROUS SOILS. ORIGIN OF MOOR-LAND. 311 

The practical benefits of draining, therefore, may be stated generally 
as follows : — 

A. It is equivalent not only to a change of soil, but also to a change 
of climate, both in reference to the growth of plants and to the health 
of the population. 

B. It is equivalent also to a deepening of the soil, both by removing 
the water and by allowing those noxious ingredients to be washed out 
of the subsoil which had previously prevented the roots from descending. 

C. It is a necessary preparation to the many other means of im- 
provement which may be applied to the land. 

You will now be able to perceive in what way it is possible that 
even light and sandy soils, or such as lie on a sloping surface, may be 
greatly benefitted by draining. Where no open outlet exists under a 
loamy or sandy surface soil, any noxious matters that either sink from 
above, or ooze up from beneath, will long remain in the subsoil, and 
render it more or less unwholesome to valuable cultivated plants. But 
let such an outlet be made by the establishment of drains, and that 
which rises from beneath will be arrested, while that which descends 
from above will escape. The rain-waters passing through will wash 
the whole soil also as deep as the bottom of the drains, and the atmos- 
pheric air will accompany or follow them. 

The same remarks apply to lands which possess so great a natural 
inclination as to allow the surface water readily to flow away. Such a 
sloping surface does not necessarily dry the subsoil, free it from noxious 
substances, or permit the constant access of the air. Small feeders of 
water occasionally make their way near to the surface, and linger long 
in the subsoil before they make their escape. This is in itself an evil ; 
but when such springs are impregnated with iron the evil is greatly 
augmented, and from such a cause alone a more or less perfect barren- 
ness not unfrequently ensues. To bring such lands by degrees to a 
sound and healthy state, a mere outlet beneath is often alone sufficient. 

It is to this lingering of unwholesome waters beneath, that the origin 
of many of our moor-lands, especially on higher grounds, is in a great 
measure to be attributed. A calcareous or a ferruginous spring sends up 
its waters into the subsoil. The slow access of air from above, or it 
may be the escape of air from water itself, causes a more or less ochrey 
deposit,* which adheres to and gradually cements the stones or earthy 
particles, among which the water is lodged. Thus a layer of solid 
stone is gradually formed — the moor-land pan of many districts — which 
neither allows the roots of plants to descend nor the surface water to es- 
cape. Hopeless barrenness, therefore, slowly ensues. Coarse grasses, 
mosses, and heath, grow and accumulate upon soils not originally in- 
clined to nourish them, and by which a better herbage had previously 
been long sustained. Of such lands many tracts have been reclaimed 
by breaking up this moor-land pavement, but such an improvement, 

* If the water contain sulphate of iron, the air from above will impart to its iron an ad- 
ditional quantity of oxygen, and cause a portion of it to fall in the state oi peroxide. If the 
iron or lime be present in the state of bicarbonate, the escape of carbonic acid from the 
water vrill cause a deposit of carbonate of iron or of lime. Any of these deposits will 
cement the earthy or stony particles together. Iron, however, is sometimes held in solu- 
tion by an organic acid {crenic), which becomes insoluble, and falls along with tbe iron 
when the latter has absorbed more oxygen from the atmosphere. 



312 THEORY OF SPRINGS. 

unless preceded by a skilful drainage, can only be temporary. The 
same natural process will again begin, and the same result will follow, 
unless an outlet be provided for the waters fron:i which the petrifying 
deposit proceeds. 

It ought to be mentioned, however, that where a ready passage and 
escape for the water is provided by an efficient drainage, and especially 
in light and porous soils, the saline and other soluble substances they 
contain will be liable, in periods of heavy rain, to be more or less com- 
pletely washed out and carried off by the water that trickles through 
them. While, therefore, the establishment of drains on all soils may 
adapt and prepare them for further improvements, and may make them 
more grateful for every labour or attention that may be bestowed upon them 
— yet after drainage they must be more liberally dealt with than before, 
if the increased fertility they at first exhibit is to be permanently main- 
tained or increased. 

§ 3. Of the theory of Springs. 

In the general drainage of the land a double object is sought to be at- 
tained. In very rainy districts, the first wish of the farmer is to carry 
off the surface water from his fields — but where less rain falls, that 
which ascends from beneath in springs, attracts at least an equal share 
of the husbandman's regard. In draining, with a view to the removal 
of this latter source of superfluous moisture, a knowledge of the true 
theory of springs, as indicated by an examination of certain geological 
phenomena, is of the greatest possible service to the practical man, in 
pointing out the sources from which the water that injures his land pro- 
ceeds, as well as the lines along which it may be most efficiently and 
most economically carried off. 

1°. The rain which falls on the surface of an extensive tract of country 
partly escapes into the rivers, and partly sinks into the earth. This 
latter portion descends through the covering of soil and other loose ma- 
terials till it reaches the rocks on which they rest- If these rocks are 
porous, like many sand-stones, or are traversed by cracks and vertical 
fissures, as many sand-stones and lime-stones are, it descends through 
them also till it reaches abed, such as one of indurated clay, so close and 
compact as to resist its further passage. By this impervious bed the wa- 
ter is arrested, and is, therefore, compelled to spread itself laterally, and 
gradually to accumulate in the beds that lie above it. Thus,*if the 
outline from A to C in the annexed diagram represent the surface of an 




undulating country, in which the subjacent rocks (1, 2, 3, 4) are covered 
by a considerable thickness of loose materials, the rain which falls from 
A to B will sink more or less rapidly to the bed (1), and, if this be im- 
permeable to water, will rest there, or will slowly drain off in the di- 
rection of B and C along the inclined surface of the rock. But if (1) 
be porous, it will sink through it to the surface of the bed (2), and 



WATER IS ARRESTED BY IMPERVIOUS BEDS. 



313 



through this also, if permeable, to (3) or (4), until it reaches the stratum 
through which it cannot pass. On the surface of this latter bed, or 
among the rocks above it, the water will accumulate until, flowing 
downwards towards C, it is enabled either to sink among the deeper 
rocks, or to make its escape again to the surface. 

But if the rocks beneath, as is shown in the same diagram from E to 
F, be traversed by vertical fissures passing through two or more, or, like 
the one represented from B to E, through a great number of beds, the 
water that falls on the surface will readily find a passage downwards to 
a considerable depth, and to the same cracks the water that lodges 
among the unfissured rocks from D to E will also gradually make its way. 

The practical etfects of these several conditions on the drainage of a 
country are very obvious. If the stratum (1) be impervious to water, 
the surface from A to B may be full of water, and may urgently de- 
mand the introduction of drains, whereas if (1) and (2) be porous, the 
surface water will gradually sink, and the apparent necessity for artifi- 
cial drainage will become much less striking. On the other hand, 
where the rocks are filled with frequent cracks, as from B to C, the 
surface water may descend and disappear so rapidly, as to render 
useless the sinking of wells — and, as in dry summers, greatly to 
retard the progress of the crops, or even seriously to injure the produce 
of the harvest. In such a fissured state are the magnesian lime-stone 
rocks in some parts of the county of Durham — and such is the consequent 
scarcity of water, on some farms, that when, in long droughts, the sup- 
ply preserved in artificial tanks begins to fail, the cattle must be 
driven to water sometimes for miles, to the nearest living brook. 

2°. But water often finds its way to greater depths without passing 
through the'superior strata, and even where they are absolutely impervi- 
ous to the rains that fall upon them. Thus along the country from A to 




B, and especially towards A, the surface soil rests upon the upper edges 
of the strata. Suppose now the beds 1, 2, 3, to be impervious to water, 
the rain that falls wherever these'rocks lie immediately beneath the sur- 
face will either remain stagnant, or will flow off' by some natural drain- 
age. Thus from the highest point C in the above diagram, the water 
will descend on either hand towards a and h. At h it may remain stag- 
nant, for it cannot descend through the bed (2), which forms the bottom 
of the valley, and the same is true of the hollow c, in which other por- 
tions of the water will rest. All this tract of country, therefore, will be 
more or less cold, wet, and consequently unproductive. But let the bed 
(4), the edge (or outcroii) of which forms the surface at «, be porous or 
permeable, then the water which falls upon that spot or which descends 
from the higher grounds about C and A, will readily sink and drain off, 



314 SPRINGS PRODUCED BY VALLIES AND SLIPS. 

descending from a towards d along the inclined bed till it finds an out- 
let in the latter direction. 

Thus it may readily happen that a naturally dry and fertile valley, as 
at a, may exist at no great distance from others, h and c, which are 
marshy and insalubrious, and in which artificial drainage alone can de- 
velope the agricultural capabilities of the soil. It appears also that, 
though in any district the rocks which lie immediately beneath the sur- 
face may contain no water, and may allow none to pass through them, 
yet that other beds, perhaps at a great depth beneath, may contain much. 
It is, in fact, this accumulation of water beneath impervious beds that 
gives rise to so many natural springs, and enables us by artificial wells 
to bring water to the surface — often where the land would otherwise 
be wholly uninhabitable. 

%'^. Thus in undulating countries, where hill-sides frequently pre- 
sent themselves, or vallies are scooped out among the rocks, as in the 
following wood-cut, the water that has fallen over the high grounds to- 




wards A, and has entered as above described, or has sunk down to the 
several strata 1, 2, 3, &c., will find a ready outlet along the slope of the 
valley, and will give rise to springs at «, &, c, or d^ according as the wa- 
ter has lodged in the one or the other of these beds. These springs will fill 
the surface soil with water, which will also descend into the bottom of 
the valley, and, if no sufficient outlet be provided for it, will, according 
to its quantity, give rise to a lake, a bog, or a morass. On the slope to- 
wards B the same springs are not to be expected, since the rains which 
sink through the surface on this side of the valley, and lodge in the po- 
rous rocks beneath, will, by the inclination of the beds, be drawn off in 
the opposite direction, till a second valley or some other available outlet 
present itself for their escape. This explains why the land on one side 
of a valley or of a hill is often much drier than on the other, and why, 
even in the absence of the improver's skill, an apparently more fertile 
soil may exist, and better crops be reaped. 

4°. Again, such an outlet for the waters that rest among inclined strata 
is not unfrequently afforded, without the intervention of vallies, and 
even in level or hilly countries, by the existence of slips ox faults in the 
rocks beneath. Such a slip or shifting of the beds is represented in the 
following diagram, in which B D is a crack, along which the strata from 
B to C appear to have slipped downwards, so that the thin bed (2), for 
example, which terminates at h on the one side of the crack, begins again 
at a lower level c on the other side, and so with the other beds that lie 
above and below it. None of them is exactly continuous on the oppo- 
site sides of the slip. From such cracks or faults in the beds, springs 
of water often rise to the surface, even on hill tops, as at B, and they 
may be thus thrown or forced out from either of two causes — 

1. These slips are often of considerable width, and are usually found 



SLIPS ARREST AND THROW UP THE WATER. 



315 




to be filled with impervious clay. This is the case at least among the 
coal-measures, which have been the most extensively explored. The ef- 
fect of this wall of clay is to dam back at B D the water which descends 
along the inclined beds towards C from the country beyond A, and thus 
to arrest its further progress. But the pressure of the water behind 
forces that which has reached the fault B D to seek a way upwards, and, 
as spaces not unfrequently exist between the wall of clay and the rocks 
between which it stands, the water finds a more or less ready outlet at 
the surface B, and either gushes forth as a living and welcome spring, 
or oozes out unseen among the soil, rendering it cold, wet, and unproduc- 
tive. Thus from b the water accumulated in the bed (2) may rise to the 
surface, or from / that which exists in (4), or from any other bed in 
which water exists, and from almost any depth. 

2. But even where no such wall of clay exists, the waters may still 
find their way to the surface along lines of fault, and from great depths. 
Thus suppose the thin bed (2) to be full of water, and that it is covered 
by an impervious bed (1), then the water which tends downwards from 
a to b will be arrested at the fault, and dammed back by the impervi- 
ous extremity of (1) against which it now rests. If an outlet can be 
found, it will therefore lise towards the surface. And as the rocks incline 
upwards in the direction of A, the pressure from behind may easily cause 
the water to ascend to the summit of the hill at B, and to gush out in a 
more or less copious spring. 

5°. Where no natural outlets of the kind above described exist in a 
district, there may be a great scarcity of water on the surface, while abun- 
dance, as we have already seen (2^^), may exist in the rocks beneath, 
ready and willing to rise if a passage be opened for it. Such is the case 
with the site of the city of London, represented below : — 



St. Alban's. 



Ilampstead 

! 



London. Thames. Sydenham. 



Knockholt. 




SECTION ACROSS THE LONDON BASIN FROM ST. ALBAN'S TO KNOCKHOLT.| 

(Buckland^s Bridgewater Treatise^ plate 69.) 
1. Marine Sand. 2. London Clay (almost impermeable). 3. Plastic Clay and Sand. 
4. Chalk, both full of water. 

The rain-water which falls between a and A, on the one hand, and 

upon the plastic clay and chalk between d and B on the other, sinks into 

the.se two beds and rests in them till it finds an escape. It cannot rise 

through the great thickness of impervious clay on which London and its 

27 



316 ARTESIAN WELLS. — SPRINGS IN BESERTS AND PARCHED PLAINS. 

neighborhood stands, unless where wells are sunk, as above represented at 
a, &, c, d, either into the plastic clay (3), or into the chalk (4), when the 
water ascends copiously till it reaches the general level of the country 
about St. Alban's, the lowest part of the basin where the permeable beds 
form the surface. Hence in the vale of the Thames at h, it rises above 
the surface, and forms a living spring, while at other places, as at a, c, c?, 
it has still to be pumped up from a greater or less depth.* It is the ex- 
istence of water beneath the surface where the soils rest on impermea- 
ble beds, and the known tendency of these waters to rise when a boring 
is sunk to them, that have given rise to the establishment of Artesian^ 
wells, so frequently executed, and with so much success, in recent times. 
There is probably no geological fact that promises hereafter to be of more 
practical value to mankind, when good government and the arts of peace 
shall obtain a permanent resting-place in those countries where, without 
irrigation, the soil remains hopelessly barren. Wherever a living spring 
bursts out in the sands of Arabia, in the African deserts, or in the parched 
plains of South America, an island of perennial verdure delights the 
eye of the weary traveller, and wherever in such countries the labour 
of man has been expended in digging wells, and in raising water from 
them for artificial irrigation, the same beanty and fertility always ap- 
pear. It has recently been found that the oases of Thebes and Garba, 
in Upper Egypt, where the blown sands now hold a scarcely disputed 
dominion, are almost riddled with wells sunk by the ancient Egyptians, 
but for the greater part long since filled up. The re-opening of such 
wells might restore to these regions their long-lost fertility, as the sink- 
ing of new ones by our easier and more economical methods might re- 
claim many other wide tracts, and convert them to the use of man. In 
contemplating what man may do, when his angry passions and his preju- 
dices do not interfere with the exercise of his natural dominion over 
dead matter, it is not unreasonable to hope that, guided by such indica- 
tions of natural science, human industry may hereafter, by slow degrees, 
re-establish its power in long-deserted regions of country, spreading 
abundance over the broad wilderness, staying the Arab's wandering foot, 
and fixing his household in a permanent and plenteous home. 

6°. It not unfrequently happens that alternate layers of sand and clay 
overspread the rocks of a country, and act in arresting or in thrmving out 
the surface water in the same manner as the solid strata beneath. Thus 




* In Janwary 1S40, there were stated to be in the London clay upwards of 200 such wells, 
of which 174 were in London, and of which latter 30 taken together were known to yield 30 
millions of gallons weekly. This number of wells has since been increased, and is still 
increasing. The borings are generally carried down into the chalk, because the water which 
ascends from the plastic clay has been found to bring with it much sand, which both ob- 
structs the pipes and is injurious to the pumps. 

t So called from the district of Artois, in France, in which it was formerly supposed that 
such borings had been longest or most extensively practised. 



EFFECT OF ALTER^'ATE LAYERS OF SAND AND CLAY. 317 

under the surface A B here represented, alternate layers of sand and clay 
overspread the inclined beds of rock, and alone affect not only the qual- 
ity but the state of dryness also of the soil. 

The rain which falls on the upper bed of sand will sink no further 
than the first bed of clay, and will appear as a spring, or will form a 
wet band along the side of the hill, at a. That which falls or exists 
in the second bed of sand will in like manner come to day at 6, c, and 
d, e, filling the two vallies more or less with water, and forming wet 
tracts of country resting upon a lower bed of impervious clay. 

In endeavouring to form a satisfactory opinion as to the best mode of 
draining a piece of land, it is of great importance to be able to deter- 
mine not only the immediate natural source of the water we are de- 
sirous to remove, but also the probable quantity it may be necessary to car- 
ry off, and the perynaneiice of the supply. It is well known, for example, 
that in many spots, when the accumulated waters are once carried off, 
there remains only a small and probably intermitting supply, for which 
an outlet is afterwards to be left and kept open ; while in other locahtiea 
a constant stream of water is seen to pass along the drains. In connec- 
tion with this point it is of consequence to make out whether the water 
is thrown out by surface clays, as in this latter diagram, or flows from 
among the solid rocks at a greater or less depth — as shown in the pre- 
ceding wood-cuts. That which is thrown out by beds of clay is in 
most cases derived only from the rains that fall, and is, therefore, liable 
to intermit, to cease altogether, or to become more copious, according as 
the season is Axy or otherwise ; while that which escapes from a bed 
of rock, being independent of the seasons, will seldom vary in quantity. 
Thus it happens that where surface water only stagnates in the soil of a 
district, a warm, dry, and long continued summer may cause it to yield a 
crop of unusual excellence, while other soils fed by springs from be- 
neath may, even in such seasons, still retain moisture enough to render 
them unfit to rear and ripen a profitable crop of corn. 

7°. There remains one other interesting principle connected with this 
subject, which I must briefly explain to you. Let C and D in the aQ-' 




companying wood-cut be two impervious beds through which the water 
finds no escape, and from which the rains pass off' only by the natural in- 
clination of the ground, and let E be a porous bed from which the water 
finds a ready escape somewhere towards the right. Then if a boring be 
sunk through C and D in any part of this tract of country, the water 
will descend, and will be absorbed by the bed E. Such dry, porous, 
or absorbent beds exist in many localities, and the skilful drainer may 
occasionally avail himself of their aid in easily and effectually freeing 
land from water, which could not without great cost be permanently 
drained by any other method. Where water collects on a surface rest- 
ing upon chalk, or upon the loose sands beneath it, this method of boring 



318 



PLOUGHING AND SUBSOILING. 



is frequently bad recourse to in some of our southern counties. One 
danger, however, is to be guarded against in trying ibis method, that the 
bore-rod, namely, may enter a bed which is full of water, and from 
which, as in Artesian wells, it may readily, and in considerable quan- 
tity, ascend. Such a boring it is obvious would only add to the evil, and 
might render necessary a longer outlay in establishing an efficient sys- 
tem of drainage by the ordinary method, thar^ would otherwise have 
been required.* 

I do not enter into any further details in regard to the application of 
these principles to the practice of draining, being satisfied that when 
you have once mastered the principles themselves, the applications 
will readily suggest themselves to your own minds when circumstances 
require it. 

§ 4. Of ploughing and suhsoiling. 

I. Ploughing. — Apart from the obvious effect of ploughing the land, 
in destroying weeds and insects, the immediate advantage sought for 
by the farmer is the reduction of his soil to a state of minute division. 
In this state it is not only more pervious to the roots of his corn, but it 
also gives a more ready admission to the air and to water. 

Of the good effects produced by the easy descent and escape of water 
from the surface, I have already spoken (p. 306), but the permeability 
of the soil to air is no less useful in developing its natural powers of pro- 
duction. How important the presence of the air is both to the main- 
tenance of animal and to the support of vegetable life, we have had 
frequent occasion to observe. By its oxygen the breathing of animals 
is sustained, and by its carbonic acid the living plant is fed. On the 
earthy particles, of which the soil consists also, the influence of these 
gaseous substances, though not so visible and striking, is of almost equal 
consequence in the economy of nature. Among other immediate bene- 
fits derived from the free access of air into the soil, we may enumerate 
the following : — 

1°. The presence of oxygen in the soil is necessary to the healthy 
germination of all seeds (Lee. VII.), and it is chiefly because they are 
placed beyond its reach, that those of many plants remain buried for 
years without signs of life, though they freely sprout when again brought 



• It sometimes happens that in sinking an old well deeper 
for the purpose of obtaining a better supply of water, the 
original springs disappear altogether. This is owing to the 
occurrence at this greater depth, of an absorbent bed, in 
in which the water disappears. By descending still further, 
a second supply of water may often be found, but which 
will naturally ascend no further than the absorbent bed, by 
which the whole supply will be drunk up, if not prevented by 
the insertion of a metal pipe. Advantage is sometimes 
taken of the known existence of such absorbent strata, not 
only for the purposes of draining, but also for removing 
waste water of various kinds. An interesting example of 
such application is to be seen at St. Denis, in the Place aux 
Gueldres, where the water from the bed / at the depth of 
200 feet ascends through the inner tube a — from another bed 
c, at IGO feet, through the tube b — while between it and the 
outermost tube, through the space c, it is sent down again 
after it has been employed in washing the square, and disap- 
pears in the absorbent stratum d. 



d 



SP 



<3s 



y 



DECOMPOSITION OF ROCKY MOUNTAINS. 319 

to the surface and exposed to the air. We have also seen reason to believe 
(Lee. v., § 2), that the roots of living'plants require a supply of oxygen 
in order that they may be maintained in a healthy condition. Such a 
supply can only be obtained where the soil is sufficiently open to per- 
mit the free circulation of the air among its pores. 

2*^. In the presence of air the decomposition of the vegetable matter 
of the soil proceeds more rapidly — it is more speedily resolved into those 
simplerformsofniatter,carbonicacidand water chiefly (Lee. VIII.), which 
are fitted to minister to the growth of new vegetable races. In the ab- 
sence of the air also, not only does this decomposition proceed more 
slowly, but the substances immediately produced by it are frequently 
unwholesome to the plant, and therefore fitted to injure, or materially to 
retard, its growth. 

3°. When the oxygen of the air is more or less excluded, the vege- 
table matter of the soil takes this element from such of the earthy sub- 
stances as it is capable of decomposing, and reduces them to a lower 
state of oxidation. Thus it converts the red or ^er-oxide of iron into 
the prot-oxide (Lee. X., § 1), and it acts in a similar manner upon the 
oxides of manganese. It also takes their oxygen from the sulphates 
(as from gypsum), and converts them into sulphurets. These lower 
oxides of iron and manganese are injurious to vegetation, and it is one of 
the beneficial purposes served by turning up the soil in ploughing, or by 
otherwise loosening it so as to allow the free admission of atmospheric 
air, that the natural production of these oxides is either in a great mea- 
sure prevented, or that when produced they speedily become harmless 
again by the absorption of an additional dose of oxygen. 

4°. Further, there are few soils which do not contain, in some quan- 
tity, fragments of one or other of those compound mineral substances ol 
which, in a previous lecture, (xii., p. 374), we have seen the crystalline 
rocks to consist — of hornblende, of mica, of felspar, &c., in a decom- 
posing state. From these minerals, as they decompose, the soil, and 
therefore the plants that grow in it, derive new supplies of several of 
those inorganic substances which are necessary to the healthy nourish-' 
ment of cultivated crops. The continued decomposition of these mine- 
ral fragments is aided by the access of air, and near its surface, in an es- 
pecial manner, by the carbonic acid which the air contains. A state of 
porosity, therefore, or a frequent exposure to the air, is favourable to the 
growth of the plant, by presenting to its roots a larger abundance not 
only of organic but also of inorganic food. 

5°. Again, that production of ammonia and of nitric acid in the soil, 
to which I drew your especial attention on a former occasion (Lee. VIII., 
§ 5 & 6), as apparently of so much consequence to vegetable life, takes 
place more rapidly, and in larger quantity, the more frequently the land 
is turned by the plough, broken by the clod-crusher, or stirred up by the 
harrow. Whatever amount of ehher of these compounds, also, the 
surface soil is capable of extracting from the atmosphere, the entire 
quantity thus absorbed will evidently be greater, and its distribution 
more uniform, the more completely the ivhole soil has been exposed to 
its influence. It is for this, among other reasons, that, as every farmer 
knows, the better he can plough and pulverise his land, the more abua- 
dant in general are the crops he is likely to reap. 
27* 



320 EFFECT OF THE SUBSOIL-PLOUGH. — AUXILIARY TO THE DRAIN. 

6°. Nor lastly, though in great part a mechanical beneJBt, is it one of 
little moment that when thus every where pervious to the air, the roots 
also can penetrate the soil in every direction. None of the food around them 
is shut up from the approach of their numerous fibres, nor are they pre- 
vented, by the presence of noxious substances, from throwing out 
branches in every direction. A deep soil is not absolutely necessary for 
the production of valuable crops. A well-pulverised and mellow soil, 
to which the air and the roots have every where ready access, will, 
though shallow, less frequently disappoint the hopes of the husbandman, 
— than where a greater depth prevails, less permeable to the air, and 
therefore less wholesome to the growing roots. 

II. Subsoil Ploughing. — And yet, as a general rule, it cannot be de- 
nied that a deep soil is greatly superior in value to a shallow soil of the 
same nature. It is so both to the owner and to the occupier, though in 
too many cases the available qualities of deep soils have hitherto been 
more or less overlooked and neglected. 

The general theoretical principle on this subject— that the deeper the 
soil the longer it may be cropped without the risk of exhaustion, and the 
greater the variety of crops, deep as well as shallow-rooted, which may 
be grown upon it — is so reasonable in itself, as to command a ready 
acquiescence. But a soil is virtually shallow where a few inches of 
porous earth, often turned by the plough, rest upon a subsoil, hard, stiflT, 
and almost impervious, — and the practical farmer will rarely be willing 
to allow the depth of the latter to influence his opinion in regard to the 
general value of the land. And in this he is so far correct, that a sub- 
soil must be dried, opened up, mellowed by the air, and rendered at 
once pervious and wholesome to the roots of plants, before it can be 
made available for the grov/th of corn. This may be effected, after 
draining, by the use of the subsoil plough, an instrument at present, I be- 
lieve, unequalled for giving a real, practical, and money-value to stiff 
and hitherto almost worthless clayey subsoils. It is an auxiliary both 
to the surface plough and to the drain, and the source of its efficacy will 
appear from the following considerations. 

l'^. The surface plough turns over and loosens the soil to the depth 
of 6 to 10 inches — the subsoil plough tears open and loosens it to a fur- 
ther depth of 8 or 10 inches. Thus the water obtains a more easy de- 
scent, and the air penetrates, and the roots more readily make their 
way among the particles of the under-soil. So far it is an auxiliary to 
the common plough, and assists it in aerating and mellowing the soil. 

2°. But though it opens up the soil for a time to a greater depth, the 
subsoil plough will in most cases afford no permanent cure for the defi- 
ciencies of the subsoil, if unaided by the drain. If the soil rests upon 
an indurated substratum — upon a calcareous or ochrey pan — this plough 
may tear it up, may thus allow the surface water to sink, and may 
greatly benefit the land ; but the same petrifying action will again recur, 
and the benefit of the subsoiling will slowly disappear. Or, if the sub- 
soil contain some noxious ingredients, such as salts of iron, which the 
admission of air is fitted to render harmless, then the use of this plough 
may afibrd a partial amelioration. But in this case, also, the effect will 
be only temporary; since the source of the evil has not been removed, 
the same noxious compounds will again be naturally produced, or 



PREVIOUS DRYNESS OF THE SUBSOIL NECESSARY. 321 

will again, in fresh supplies, be conveyed into the soil by springs. Or, 
if the subsoil be a stiff clay, containing no noxious ingredient, it may be 
cut, or for the time torn asunder, but scarcely will the plough have 
passed over it till the particles will be again cemented together, and pro- 
bably, by the end of a single season at the furthest, the under-soil may 
be as solid and impermeable as ever. 

It is as the follower of the drain, therefore, in the course of improve- 
ment, that the subsoil plough finds its most beneficial and most economi- 
cal use. After land has been drained, the water may still too slowly 
pass away, or the air may have loo imperfect an entrance into the sub- 
soil from which the drains have removed the water. In the former case, 
the subsoil plough must be employed, in order that the drains may be- 
come fully efficient ; in the latter, that the under-layers may be opened 
up to all the beneficial influences which the atmosphere is fitted to exert 
upon them. In this respect it is an auxiliary to the drain. But as the 
full effect which the subsoil plough is capable of producing upon stiff 
and clayey subsoils, can only be obtained after they have been brought 
to such a state of dryness that the sides of the cut or tear, which the 
plough has made, will not again readily cohere, it is of importance that 
the drains should be allowed a considerable time to operate before the 
use of this plough is attempted. The expense of the process is compa- 
ratively great, and this expense will be in a great measure thrown away 
upon clay lands, which are undrained, or from which the water, either 
through defective draining, or from the want of sufficient time, has not 
been able fully to flow away. There are few kinds of clay land on 
which the judicious use of this valuable instrument will not prove both 
actually and economically useful, though from the neglect of the above 
necessary precaution, it has been found to fail in the hands of some. 
Such failures, however, do not justify us in ascribing to some fancied 
defect in the instrument, or in the theory upon which its use is recom- 
mended, what necessarily arose, and could have been predicted, from 
our own neglect of an indispensable preliminary observation. The san- 
guine anticipations of its inventor, Mr. Smith, of Deanston. may not 
be fully realized, yet the value of the subsoil plough itself, and the bene- 
fits it is fitted to confer, when rightly used, appear to me to be both theo- 
retically and practically established. 

§ 5. Of deep-ploughing and trenching. 

Deep-ploughing and trenching differ from ordinary and subsoil' 
ploughing in this, — that their special object is to bring to the surface and 
to mix with the upper-soil a portion of that which has lain long at a 
considerable depth, and has been more or less undisturbed. 

The benefit of such an admixture of fresh soil is in many lo- 
calities undoubted, while in others the practical farmer is decidedly 
opposed to it. On what principle does its beneficial action depend, 
and in what circumstances is it, likely to be attended with disad- 
vantage ? 

1°. It is known that when a heavy shower of rain falls it sinks into 
the soil, and carries down with it such readily soluble substances as it 
meets with on the surface. But other substances also, which are more 



322 OBJECT AND EFFECT OF DEEP-PLOUGIIING. 

sparingly soluble, slowly and gradually find their way into the subsoil, 
and there more or less permanently remain. Among these may be reck- 
oned gypsum, and especially those silicates of potash and soda already 
spoken of (Lec.X.), as apparently so useful to corn-growing plants. Such 
substances as these naturally accumulate beyond the reach of the ordi- 
nary plough. Insoluble substances likewise slowly sink. This is well 
known to be the case with lime, when laid upon or ploughed into 
the land. So it is with clay, when mixed with a surface soil of sand or 
peat. They all descend till they get beyond the reach of the common 
plough — and more rapidly it is said (in Lincolnshire) when the land is 
laid down to grass, than when they are constantly brought to the surface 
again in arable culture. Thus it happens that after the surface soil be- 
comes exhausted of one or other of those inorganic compounds which the 
crops require, an ample supply of it may be still present in the subsoil, 
though, until turned up, unavailable for the promotion of vegetable growth. 

There can be little question, I think, that the greater success which 
attends the introduction of new implements in the hands of better in- 
structed meu, upon farms long held in arable culture, is to be ascribed 
in part to this cause. One tenant, during a-long lease, has been in the 
habit of ploughing to a depth of three, or at most, perhaps, of four 
inches — and from this surface the crops he has planted have derived their 
chief supplies of inorganic food. He has limed his land in the cus- 
tomary manner, and has laid upon it all the manure he could raise, but 
his crops have been usually indifferent, and he considers the land of com- 
paratively little value. But another tenant comes, and with better im- 
plements turns up the land to a depth of 7 or 8 inches. He thus brings 
to the surface the lime and the accumulated manures which have 7iatu- 
rally sunk, and which his predecessor had permitted year after year to 
bury themselves in his subsoil. He thus has a new, often a rich, and 
almost always a virgin soil to work upon — one which from being long bu- 
ried, may require a winter's exposure and mellowing in the air, but 
which in most cases is sure to repay him for any extra cost. The deep 
ploughing which descends to 14 inches, or the trenching which brings up 
a new soil from the depth of 20 or 30 inches, is only an extension of the 
same practice. It is justified and recommended upon precisely the 
same principle. It not only brings a new soil, containing ample nour- 
ishment, to the immediate roots of plants, but it affords them also a 
deeper and more open subsoil, through which their fibres may proceed in 
every direction in search of food. The full benefits of this deepening of 
the soil, however, can only be expected where the subsoil has previously 
been laid dry by drains ; for it matters not how deep the loosened and 
permeable soils mav be, if the accumulation of water prevent the roots 
from descen(Hng. 

2°. Two practical observations, however, may here be added, which 
the intelligent farmer will always weigh well before he hastily applies 
this theoretical principle — sound though it undoubtedly be — in a district 
with which he has no previous acquaintance. It is possible that the 
deeper soil may contain some substance decidedly noxious to vegetation. 
In such a case it would be improper at once to mix it with the upper 
soil. Good drains must be established, they must be allowed some time 
to act, and the subsoil plough will be used with advantage, before any 
portion of such an under-soil can be safely brought to the surface. The 



EFFECT OF INSECTS. IMPROVEMENT OF THE SOIL. 323 

subsoil plough and the drain, indeed, as I have already mentioned, are 
the most certain available remedies for such a stale of the subsoil. In 
many localities, however, the exposure of such an under-soiltoa winter's 
frost, or to a summer fallow, will so far improve and mellow it, as to ren- 
der it capable of being safely mixed with the surface soil. Unless, how- 
ever, this mellowing be effected at once, and before admixture, a long 
time may elapse ere the entire soil attain to its most perfect condition.* 
Again, it is known that some districts, for reasons perhaps not well un- 
derstood, are more infested than others with insects that attack the corn 
or other crops. These insects, their eggs, or their larvae, generally bury 
themselves in the undisturbed soil, immediately beyond the ordinary 
reach of the plough. If they remain wholly undisturbed during the 
preparation of the soil, some species remain in a dormant state, and the 
subsequent crop may in a great measure escape. Plough the land deep- 
er than usual, and you bring them all to the surface. Do this in the 
autumn, and leave your land unsown, and the frost of a severe winter 
may kill the greater part, so that your crops may thereafter grow in safety. 
But cover them up again along with your winter corn, or let this 
deep ploughing be done in the spring, and you bring all these insects 
within reach of the early sun, and thus call them to life in such num- 
bers as almost to ensure the destruction of your coming crop. It is to 
something of this kind that I am inclined to attribute the immediate fail- 
ures which have attended the trial of deep ploughing in certain parts of 
England. Thus in Berkshire, certain soils which are usually ploughed 
to a depth of only twomohe^, yielded almost nothing when deeper [)lough- 
ing was more lately tried upon them — the crop was almost entirely de- 
stroyed by insects. So also in the north of Yorkshire, where deep 
ploughing has recently been attempted, the wheat crop on land so treated 
was observed to suffer more from the worm than on any other spot. 
Such facts as these, therefore, show the necessity of caution on the part 
of the practical man, and especially of the land agent or steward, how- 
ever correct may be the principles on which his general practice is 
founded. Failures such as the above do not shc<^' the principle on which 
deep ploughing is recommended to be false, or the practice to be in any 
case reprehended : but it does show that a knowledge of natural local 
peculiarities, and some study of ancient local practice, may, in an im- 
portant degree, influence our mode of procedure in introducing more 
improved methods of husbandry into any old agricultural district. 

§ 6. Improvement of the soil by mixing. 
There are some soils so obviously defective in constitution, that the 
most common observer can at once pronounce them likely to be improved 
by mechanical admixtures of various kinds. Thus peaty soils abound 

' The Marquis of Tweedale, in his home-farm at Yesters, has raised his land in vahie 
eight times (from 5s. to 40s. per acre), by draining and deep ploughing. After draining, the 
fields of stiff clay, with streaks of sand in the subsoil, are turned over to a depth of 12 or 14 
inches, by two ploughs (two horses each) following one another, the under 6 inches being 
thrown on the top. In this state it is left to the winter's frost, when it falls to a yellow marly 
looking soil. It is now ploughed again to a depth of 9 or 10 inches, by which half 
the original soil is brought again to the surface. By a cross ploughing this is mixed with 
the new soil, after which the field is prepared in the usual way for turnips. But it is observed 
that if the ploughing has been so late that the subsoil has not had a proper exposure to the 
winter's cold, the land on such spots does not for many years equal that which was earlier 
ploughed. The reason is, that when once mixed up with the other soil the air has no longer 
the same easy access into its pores. 



324 EFFECTS OF CLAY AND MARL. 

too much in vegetable matter; a mixture of earthy substances, there- 
fore, of almost any common kind, is readily indicated as a means of im- 
provement. In like manner we naturally impart consistence to a sandy 
soil by an admixture of clay, and openness and porosity to stiff clays by 
the addition of sand. 

The first and obvious effect of such additions is to alter the physical 
qualities of the soil — to consolidate the peats and sands, and to loosen 
the clays. But we have already seen that the fertility of a soil, or its 
power of producing a profitable return of this or that crop, depends in 
the first place on its chemical constitution. It must contain in sufficient 
abundance all the inorganic substances which that crop requires for 
its daily food. Where this is already the case, as in a rich stiff claj^ a 
decided improvement may be produced by an admixture with siliceous 
sand, which merely separates the particles mechanically, and renders 
the whole more porous. But let the clay be deficient in some necessary 
constituent of a fertile soil, and such an addition of siliceous sand would 
not produce by any means an equal benefit. It may be proper to add 
this sand with the view of producing the mere physical alteration, but 
we must add some other substance also for the purpose of producing the 
necessary chemical change. 

The good effects which almost invariably follow from the addition of 
clay to peaty or sandy soils are due to the production at one and the same 
time of a physical and of a chemical change. They are not only ren- 
dered firmer or more solid by the admixture of clay, but they derive 
from this clay at the same time some of those mineral substances which 
tliey previously contained in less abundance. 

The addition of marl to the land acts often in a similar two-fold capa- 
city. It renders clay lands more open and friable, and to all soils brings 
an addition of carbonate, and generally of phosphate of lime, both of 
which are proved by experience to be not only very influential, but to be 
absolutely necessary to healthy vegetation. 

That much benefit to the land would in many instances accrue from 
such simple admixture^ as those above adverted to, where the means 
are available, will be readily granted. The only question on the sub- 
ject that ought to arise in the mind of a prudent man, is that v/hich is 
connected with the economy of the case. Is this the most profitable way 
in which I can spend my money? Can I employ the spare labour of 
my men and horses in any other way which will yield me a larger 
return ? It is obvious that the answer to these questions will be modi- 
fied by the circumstances of the district in which he lives. It maybe 
more profitable to drain, — or labour may be in great request and at a 
high premium, — or a larger return may be obtained by the investment 
of money in purchasing new than in improving old lands. It is quite 
true that the country at large is no gainer by the mere transfer of land 
from the hands of A to those of B, and that he is undoubtedly the most 
meritorious citizen who, by expending his money in improving the soil, 
virtually adds to the breadth of the land, in causing it to yield a larger 
produce. Yet it is no less true that the employment of individual capi- 
tal in such improvement is not to be expected generally to lake place, 
unless it be made to appear that such an investment is likely to be as 
profitable as any other within the reach of its possessor. It seems to be 



CLAY AND SAND. — SPECIAL MIXTURES. 



325 



established beyond a doubt that in very many districts no money is more 
profitably invested, or yields a quicker return, than that which is ex- 
pended in draining and subsoiling — and yet in reality one main obstacle 
to a more I'apid increase in the general produce of the British soil is the 
practical difficulty which exists in convincing the owners and occupiers 
of the soil that such is the case, or would be the case, in regard lo their 
own holdings. The more widely a knowledge of the entire subject, in 
all its bearings, becomes diffused, the less it is to be hoped will this diffi- 
culty become — for the economist, who regards the question of improve- 
ment as a mere matter of profit and loss, cannot strike a fair balance 
unless he knows the several items he may prudently introduce into each 
side of his account. 

Thus in reference to the special point now before us, it seems reason- 
able to believe that, in a country such as that here represented, where 
alternate hills of sand (3), and hollows, and flats of clay (4) occur, there 




may be many spots where both kinds of soil — being near each other — 
might be improved by mutual admixture, at a cost of labour which the 
alteration in the quality of the land might be well expected to repay. 
In this condition is a considerable portion of the eastern half of the 
county of Durham, and, especially, I may mention the neighbourhood, 
of Castle Eden, where a cold, stiff, at present often poor clay rests upon 
red, rich-looking, loamy sand, in many places easily accessible, and by 
admixture with which its agricultural capabilities may be expected to 
improve. In this locality, and in many others besides, those having a 
pecuniary interest in the land rest satisfied that their fields are incapable 
of such improvement, or would give no adequate return for the outlay 
required, without troubling themselves to collect and compare all the 
facts from which a true solution of the question can alone be drawn. 

Besides such general admixtures for the improvement of land, the 
geological formation of certain districts places within the reach of its in- 
telligent farmers means of improvement of a special kind, of which they 
may often profitably avail themselves. Thus both in Europe and Ame- 
rica the green-sand soils (Lee. XL, § 8,) are found to be very fertile, and 
the sandy portions of this formation are often within easy distance of the 
stiff clays of the gault, and of the poor soils of the chalk, with either of 
which they might be mixed with most beneficial effects. The soils that 
rest on the neiv, and even on some parts of the old red sand-stone^ are 
in like manner often within an available distance of beds of red marl of 
a very fertilizing character (Lee. XL, § 8), while in the granitic and trap 
districts the materials of which these rocks consist, if mixed withjude- 
raent, may be made materially to benefit some of the neighbouring soils. 
To this point, however, I shall draw your attention again in my next lec- 
ture, when treating of mineral manures. 



LECTURE XV. 

Improvement of the soil by chemical means. — Principles on which all manuring depends. 
Mineral, vegetable, and animal manures. — Saline manures.— Carbonates. Pearl-ash. 
— Sulphates. — Glauber salts. — Chlorides. Common salt.— Nitrates. Nitrate of soda. — 
Phosphates. Phosphate of lime. — Silicates. Silicate of potash.— Saline mixtures. — 
Vegetable ashes. — Prepared granite. — Use of lime. 

The mechanical methods of improving the soil, described in the pre- 
ceding section, are few in number and simple in theory. They are so 
important, however, to the general fertility of the land, that were they 
judiciously employed over the entire surface of our islands, they would 
alone greatly increase the average produce of the British and Irish soils. 
I may, indeed, repeat what was stated in reference to draining (p. 309), 
that the full effect of every other means of improving the soil will be 
obtained in those districts only where these mechanical methods have 
already been had recourse to. 

The chemical methods of improving the soil are founded upon the 
following principles, already discussed and established : — 

1°. That plants obtain from a fertile soil a variable proportion of their 
organic food ; — of their nitrogen probably the greatest part. 

2°. That they require inorganic food also of various kinds, and that 
this they procure solely from tbe soil. 

3°. That different species of plants require a special supply of dif- 
ferent kinds of inorganic food, or of the same kinds, in different pro- 
portions. 

4°. That of these inorganic substances one soil may abound or be 
deficient in one, and another soil in another; and that, therefore, this or 
that plant will prefer to grow on the one or the other accordingly. 

On these few principles the whole art of improving the soil by che- 
nical means — in other words, of beneficially manuring the soil — is 
founded. 

It must at the same time be borne in mind, that there are three dis- 
tinct methods of operation by which a soil may be improved : — 

1°. By re7noving from it some noxious ingredient. The only method 
by which this can be effected is by draining, — providing an outlet by 
which it may escape, or by which the rains of heaven, or water applied 
in artificial irrigation, may wash it away. 

2°. By changing the nature or state of combination of some noxious 
ingredient, which we cannot soon remove in this way ; or of some inert 
ingredient which, in its existing condition, is unfit to become food for 
plants. These are purely chemical processes, and we put them re- 
spectively in practice when we add lime to peaty soils, or to such as 
abound in sulphate of iron (Lee. X., § 1), when by admitting the air 
into the subsoil we change the prot-oxide into the per-oxide of iron, or 
when by adding certain known chemical compounds we produce simi- 
lar beneficial chemical alterations upon other compounds already exist- 
ing in the soil. 



ACTION OF CHEMICAL SUBSTANCES IN THE SOIL. 327 

3°. By adding to the soil those substances which are fitted to become 
the food of plants. This is what we do in strictly manuring the soil — 
though we are as yet unable in many cases to say whether that which 
we add promotes vegetation by actually feeding the plant and entering 
into its substance — or only by preparing food for it. There is reason to 
believe, however, that many substances, such as potash, soda, &c., act 
in several capacities, — now preparing food for the plant in the soil, now 
bearing it into the living circulation, and now actually entering into the 
perfect substance of the growing vegetable. In order to steer clear of 
the difficulty which this circumstance throws in the way of an exact 
classification of the chemical substances applied to the soil, I shall con- 
sider generally under the name of manures, all those substances which 
are usually ajyplied to the land for the 'purpose of promoting vegetable 
growth; — whether those substances be supposed to do so directly by 
feeding the plants, or only indirectly, by preparing their food, or by con- 
veying it into their circulation. 

Manures, then, in this sense, are either simple, like common salt 
and nitrate of soda, or they are mixed, like farm-yard manure and the 
numerous artificial manures now on sale. Or, again, they consist of 
substances of mineral, of vegetable, or of animal origin. The latter is 
the more natural, and is by far the most useful, classification. We 
shall, therefore, consider the various substances employed in improving 
the soil — or what is in substance the same thing, in promoting vegetation, 
—in the following order : — 

I''. Mineral manures — including those substances, whether simple or 
mixed, which are of mineral origin, or which consist entirely of inor- 
ganic or mineral matter. Under this head the use of lime and of the 
ashes of plants will fall to be considered. 

2°. Vegetable manures. — These are all of natural origin, and are all 
mixtures of organic and inorganic matter. 

3"^. Animal manures, which are also mixtures, but, owing to tlieir im- 
mediate origin, differ remarkably in constitution from vegetable sub- 
stances. 

§1.0/* mineral manures. 

Mineral manures may be conveniently considered under the two heads 
of saline and earthy manures. 

A. SALINE MANURES. 

1°. Carbonate of potash. — This substance, in the form either of crude 
potash or of the pearl-ash of the shops, has hitherto been considered too 
high in price to admit of its extensive application in the culture of the 
land. 

2^^. Carbonate of soda. — This remark, however, does not apply to 
the carbonate of soda (common soda of the shops), which is sufficientlv 
low in price (d£ll. a ton) to allow of its being applied with advantage 
under many circumstances. In the case of grass-lands, which are over- 
run with moss — of such as abound largely in vegetable matter or in 
noxious sulphate of iron — a weak solution applied with a water-cart 
might be expected to produce good results. It might be applied in the 
same way to fields of sprouting corn, or in fine powder as a top-dressing 
28 



328 QUANTITY OF SALINE MANURES USEFUL TO THE SOIL. 

in moist weather — and generally wherever wood ashes are found useful 
to vegetation. 

Many experiments have shown that both of these substances may be 
employed in the field with advantage to the growing crop — but further 
trials are necessary to show how far the practical farmer may safely use 
them with the hope of profit. In gardening they greatly hasten the 
growth and increase the produce of the strawberry,* and in garden cul- 
ture, generally, where the cost of the manure employed is of less con- 
sequence, more extended trials would, no doubt, lead to useful results. 

The quantity of these substances which ought to be applied to our 
fields, in order to produce the beneficial effect which theory and practice 
both lead us to expect, will depend much upon the nature of the soil in 
each locality and on the kind of manuring to which it has previously 
been subjected. By referring to our previous calculations (Lee. X., § 
3), it will be seen that upwards of 800 lbs. of these carbonatesf would 
be necessary to replace all that is extracted from the soil by the entire 
crops during a four years' rotation. But m good husbandry every thing 
is returned to the soil in the form of manure which is not actually sent 
to market and sold for money. That is — the grain only of the corn 
crops, the dairy produce, and the live stock, are carried off the land.| 
Less than 40 lbs. peracreof the mixed carbonates would replace all that 
is contained in the grain, and if we suppose as much to be present in the 
other produce sold, we have 80 lbs. for the quantity necessary to be re- 
stored to the land by the good husbandman every four years, in order to 
keep his farm permanently in the same condition. There are, however, 
in most soils, certain natural sources of supply (Lee. X., § 1^)? by which 
new portions of these alkalies are continually convej^ed to them. Hence 
it is seldom necessary to add to the land as much of these substances as 
we carry off; and therefore from 40 to 60 lbs. per acre, of either of 
them, may be considered as about the largest quantity which, in a well- 
managed farm, need be added in order to give a fair trial to their agri- 
cultural value. Half a cwt. of the potash will cost less than 15s., and 
of the soda less than 6s., or of a mixture, in equal quantities, less than 
21s. at their present prices. 

Theory of the action of potash and soda. 

But upon what theoretical grounds is the beneficial action of potash 
and soda upon vegetation explained? This question, to which I have 
already more than once drawn your attention (Lee. V., § 2, and IX., 
§ 4), it will be proper here briefly to consider. 

a. The first and most obvious purpose, served by the presence of these 
alkalies in the soil, is that of yielding readily to the growing plant such 
a full supply of each as may be essential to its healthy growth. If the 
roots can collect them from the soil slowly only, and with difficulty, the 
growth of the plant will necessarily be retarded ; while in situations 
where they naturally abound, or are artificially supplied, the crops will 

* Mr. Fleming, of Baroclian, has informed me that he found this to be the case with the 
co:?imon poiash; and Mr. Campbell, of Islay, with the common soda of the shops. They 
should be applied early in the spring, and in the state of a very weak solution. VS'ood- 
ashes would probably produce a similar eflect. 

t 390 Ib.i;. of dry pearl ash and 440 lbs. of crystallized carbonate of soda. 

:; In bud husbandry much more is carried off the land by the waste of liquid and other 
manure,— Sec the succeeding ehaptei", " On animal ?na?iure$." 



POTASH AND SODA PREPARE THE FOOD OF PLANTS. 329 

as certainly prove both more early and more abundant — provided no 
other essential food be deficient in the soil. 

In reference to this mode of action it will occur to you that potash is 
the more likely of the two to be beneficial to our cultivated crops, inas- 
much as the ash of those plants which are raised for food is generally 
much more rich in potash than in soda.* But this may possibly arise 
from the more abundant presence of potash in the soil generally, since 
some chemists are of opinion that soda may take the place of potash in 
the interior of plants, without materially affecting their groivth.f This 
hypothesis, whatever may be its theoretical value, will prove useful to 
practical agriculture if it lead to experiments from which the relative 
action of each of these carbonates, in the same circumstances, may be 
deduced, — and the specific influence of each, in promoting the growth of 
particular plants, in some degree determined. Potash (or wood-ashes) 
aids the growth of corn after turnips or potatoes (Lampadius) — would 
soda do the same? Carbonate of soda assists in a remarkable manner 
the growth of buck-wheat (Sprengel) — would the same good effects fol- 
low from the use of potash ? 

b. Another purpose which these carbonates are supposed to serve, i$ 
that of combining with, and rendering soluble, the vegetable matter of 
the soil, so as to bring it into a state in which it may be readily con- 
veyed into the roots of plants. They may in this case be said to pre- 
pare the food of plants. That they are really capable of forming 
readily soluble compounds with the humic acid, and with certain other 
organic substances which exist in the soil, is certain. Those, however, 
who maintain with Liebig that plants imbibe all their carbon in the 
form of carbonic acid, will not be willing to admit that this property of 
the above carbonates can either render them useful to vegetation, or ac- 
count for the beneficial action they have so often been observed to exer- 
cise. From this opinion we have already seen reason (Lee. IV., § 2), 
to dissent, and we are prepared, therefore, to concede that potash and 
soda, in the form of carbonates, may act beneficially upon vegetation — 
by preparing the organic matter of the soil for entering into the roots of 
plants, and thus administering to their growth. 

This preparation also may be effected either by their directly com- 
bining with the organic matter, as they are known to do with the humic 
and other acids which exist in the soil ; or by their disposing this or- 
ganic matter, at the expense of the air and of moisture, to form new 
chemical compounds which shall be capable of entering into the vege- 
table circulation. This disposing influence of the alkalies, and even of 
lime, is familiar to chemists under many other circumstances. 

This mode of action of the carbonates of potash and soda can be ex- 
ercised in its fullest extent only where vegetable matter abounds in the 
soil. It is stated by SprengelJ accordingly, as the result of experiment, 
that they are most useful where vegetable matter is plentiful, and that 
they ought to be employed more sparingly, and with some degree of 
hesitation, where such organic matter is deficient. 

c. We have already seen, during our study of the composition of tha 

• See the tabular details given in Lecture X., § 3. 
t Berzelius Chimie, VI., p. 733 (Edit. 1832.) 
X Lehre vom Diinger, p. 402. 



^^f 



330 POTASH AND SODA RENDER SILICA SOLUBLE, ETC. 



ash of plants (Lee. X, § 3, 4), how very important a substance silica is, 
especially to the grasses and to the stems of our various corn-bearing 
plants. This silica exists very frequently in the soil in a state in which 
it is insoluble in pure water, and yet is more or less readily taken up by 
water containing carbonate of potash or carbonate of soda. And as 
there is every reason to believe that nearly all the silica they contain is 
actually conveyed into the circulation of plants by the agency of potash 
and soda,* it is not unlikely that a portion of the beneficial action of 
these substances, especially upon the grass and corn crops, may be due 
to the quantity of silica they are the means of conveying into the interior 
of the growing plants. 

d. Another mode in which these substances act, more obscurely, per- 
haps, though not less certainly, is by disposing the organic matters con- 
tained in the sap of the plant to form such new combinations as may be 
required for the production of the several parts of the living vegetable. 
I have on a former occasion illustrated f to you the very remarkable 
changes which starch may be made to undergo, without any essential 
alteration in its chemical composition — how gum and sugar may be suc- 
cessively produced from it, without either loss or gain in respect of its 
original elementary constitution. We have seen also how the presence 
of a comparatively minute quantity of diastase (Lee. VI., § 8), or of sul- 
phuric acid (Lee. VI., § 6), is capable of inducing such changes, first 
rendering the starch soluble, and then converting it into gum and into 
sugar. Analogous, though somewhat different changes, are induced by 
the presence in certain solutions of small quantities of potashj or soda, 
as, for example, in milk — the addition of carbonate of soda to which 
gradually causes (persuades?) the whole of the sugar it contains to be 
converted into the acid of milk. Such changes also must be produced 
or facilitated by the presence of acid and of alkaline substances in the 
sap of plants ; and, though we can as yet only guess at the precise na- 
ture of these changes, yet there seems good ground for believing that to 
facilitate their production is one of the many purposes served by the con- 
stant presence of inorganic substances in the sap of plants. Indeed, so 
important is this function considered by some writers upon the nourish- 
ment of plants,"^ that they are inclined to ascribe to it, erroneously how- 
ever, as I believe, the main influence upon vegetation, of nearly all the 
inorganic substances which are found in the ash of plants, and there- 
fore are known to enter into their circulation. 

e. I only allude to one other way in which these substances may be 
supposed to have an influence upon vegetation. We have already seen|| 
how important a part the nitric acid produced in the atmosphere or in 
the soil may be supposed to perform in the general vegetation of the globe. 
This acid is observed to be more abundantly — either fixed or actually 
produced in the soils or composts which contain much potash or soda. 
It may be, therefore, that in adding either of these to our fields we give 

* In the state of silicates. — See Lee. V., § 2, and Lee. X., § 1. 
t Lecture VI., § 6. 

X It is also shown (Lee. VI., § 6,) that, by means of potash, woody fibre may be converted 
into starch. 
§ See especially Illubeck's Ern'dhrung der Pflanzen und Statik des Landbaues. 
U Lee. VIII., § 5, 6, 7. 



1 

8. I 



EFFECTS PRODUCED BY SULPHATE OF SODA. 331 

to the soil the means of bringing within the reach of the roots of our 
crops a more ready supply of nitric acid, and hence of nitrogen, so neces- 
sary a part of their daily food. 

3°. Sulphates of Potash and Soda. — It is nearly 100 years since Dr. 
Home, of Edinburgh, observed that these salts produced a beneficial 
effect upon vegetation. Applied to grov/ing corn, they increased the 
produce by one-fourth. Other experiments, since made in Germany, 
have shown that they may be applied with manifest advantage both to 
field crops and to fruit trees (Sprengel), but the price has hitherto been 
considered too high to admit of their being economically used in ordinary 
husbandry. 

The manufacture of sulphate of soda in England, however, has of 

late years become so much extended, and the price in consequence so 

much reduced, that I was induced in the spring of the year 1841,* 

again to recommend it to the attention of the practical agriculturists 

of the country — as likely, either alone or mixed with other substances, 

to increase in many localities not only the produce but the profit also to 

be derived from the land.* Many experiments were in consequence 

made in various parts of the country, the details of some of which are 

given in the Appendix. f When applied at the rate of half a cwt. of 

the dry salt (or one cwt. of crystals) per acre, it produced little effect 

upon the hay crop, the quantity being probably too small. Applied to 

hay and rye, at the rate of 84 lbs. of the dry salt, and to potatoes at the 

rate of 100 lbs., it gave per imperial acre, with 

Undressed. Dressed with Sulphate. Increase. 

Hay 4480 lbs. 5288 lbs. 808 lbs. 

ITT- -D S ^rain, 640 lbs. 896 lbs. 256 lbs. 

AVmter Rye ^ |^^^^^^ ^^gg j^^^ 4g0g ^^3. 512 ibs. 

Potatoes .... 16i tons. 18i tons. If.tons. 

The grain of the dressed rye was much heavier than that of the other, 
and, though nitrate of soda and sal-ammoniac applied to other parts of 
the same^eld caused a larger increase in the crop of rye, yet the increase 
obtained by the use of the sulphate was cheaper per bushel than that ob- 
tained by the use of either of the other substances. 

On beans and peas also the effect produced by it (Appendix, No. III.) 
was very striking — its action being exerted not upon the straw but upon 
the pods, increasing their number and enlarging their size. 

The results of these experiments, therefore, are such as to encourage 
further trials. The quantity applied should not be less than one cwt. 
of the dry salt per acre, and it should be put on either in the state of a 
very weak solution with a water-cart, or sprinkled on the young crop 
when the ground is moist or when rain is soon expected. 

4°. Sulphate of Magnesia {Ejjsom Salts) was found by Dr. Home to 
promote vegetation almost in an equal degree with the sulphates of potash 
and soda, but the usually high price of this compound, among other 
causes, has hitherto prevented it from being tried upon an extensive 
scale. The manufacture of this article also has of late years, however, 

* When the publication of these lectures was commenced. 

t See Appendix, also published in the form of a separate tract—" Suggestions for Expcri- 
meats in Practical Agriculture," No. I. 
28* 



332 USE OF SULPHATE OF LIME OR GYPSUM. 



been so much extended and simplified, that the refined salts for medi 
cinal purposes may be purchased as low as 8s. a cvvt.,* and the impure 
salts of the Yorkshire and other alum works at a much lower rate. So 
much capital indeed has now been embarked in the manufacture of the 
sulphates and carbonates of soda and magnesia (Lee. IX., § 4), and 
it is so desirable on many accounts to discover new outlets for the pro- 
ducts of these important manufactories, that were there only theoretical 
reasons for believing them likely to benefit practical agriculture, it would 
be desirable to make trial of their effects upon the land. But their 
favourable influence has already been shown, and it remains, therefore, 
only to work out the details by which their application to this or that 
soil or crop shall be so regulated as to yield a fair and constant profit to 
the farmer who employs them. 

I have elsewhere (Appendix, No. I.) recommended the application of 
sulphate of soda at the rate of i cvvt. of the dry salt or of 2 cvvt. of crys- 
tals (cost 10s. or lis.) per acre. The Epsom salts are only sold in crys- 
tals, and 1^ cvvtt. (cost 12s.) in this form should be nearly equal in effi- 
cacy upon the land to 2 cvvt. of crystallized sulphate of soda. In this 
proportion, therefore, it would be proper to apply it to the young crops, 
especially of wheat, clover, peas, beans, and other leguminous plants. 

Sulphate of Lime {Gypsum) has been long and extensively applied to 
the land in various countries and to various crops. In Germany its influ- 
ence has been most generally beneficial upon grass and red clover, while 
in many parts of the United States it is applied with advantage to almost 
every crop. In the former country and in England, it is usually dusted 
over the young plants in early spring; in America it is frequently sown 
with the seed, or, in the case of potatoes, put into the drills or holes 
along with the manure. The propriety of adopting the one rather than 
the other of these methods will depend upon the nature of the soil and 
upon the climate. Gypsum requires much water to dissolve it, and in 
dry soils, climates, or seasons, it might readily fail to influence the crop 
at all, if applied in the form of a top-dressing only. 

It would appear that the time and mode of its application has more 
influence upon its activity than we might suppose — since, according to 
Professor Korte, whpn applied to clover at different periods in the spring, 
the produce of different parts of the same field was in the following 
proportions : — 

Undressed • . 100 lbs. 

Top dressed on the 30th of March 132 lbs. 

'* " 13th of April 140 lbs. 

" 27th of April 156 Ibs.f 

The effect of a top dressing of gypsum seems therefore to be greatest 
when it is applied after the leaves have been pretty well developed. J 

Theory of the action of these sulp>hates^ 
a. It does not seem difficult now to account for the general action of 

• From the Messrs. Cookson's, of the Jarrow Alkali Works, near Newcastle. 

t Mdglinsche Jahrbucher, I., p. 85, quoted in Illubek's Pflanzenn'dhrimg. 

X Can tlie result here mentioned have any connexion with the fact observed by Peschier, 
that gypsum laid upon the leaves of plants is gradually converted into carbonate, itssulphurio 
acid being absorbed 1 



a 



THEORY OF THE ACTION OF THESE SULPHATES. 333 

these several sulphates of potash, soda, magnesia, and lime. The ex- 
planation may be deduced partly from recent chemical analyses, and 
partiyfrom agricultural experiments more lately made by practical men. 
It has been found, for example, that sulphur is a constant and appa- 
rently necessary constituent of the gluten and albumen of the several 
varieties of grain, and of the legumin which forms the largest part 
of the substance of the pea, the bean, the vetch, and of the seeds of 
other leguminous plants. This sulphur they must obtain from the soil, 
and one cause of the efficacy of the above sulphates is unquestionably 
that they are fitted easily to yield to the growing plant the supply 
of sulphur they necessarily require — while, if they are more efficacious 
upon the leguminous than upon other kinds of plants, it is because 
the latter produce a larger proportion of that kind of organic matter in 
which sulphur is constantly present. 

That such is really the true explanation of their general action is 
proved by the observation — that sulphuric acid applied to the land in a 
very diluted state exerts an influence upon the crops precisely similar to 
that observed when gypsum or sulphate of soda* is used. 

In reference to this mode of action it is of consequence to know the 
relative efficiency'- of the several salts. This will obviously depend upon 
the relative proportions of sulphur or sulphuric acid they contain — sup- 
posing the circumstances in which they are applied to be equally favour- 
able to the introduction of each into the circulation of the plant. Their 
relative value upon this view is as follows: — 

100 lbs. of burned gypsum are equal to, or contain as much sulphuric 
acid as, 

126 lbs. of common or unburned gypsum. 
128 lbs. of sulphate of potash. 
104 lbs. of sulphate of soda — dry. 
235 lbs. of sulphate of soda — crystallized. 
180 lbs. of sulphate of magnesia — crystallized. 
And as of all these the gypsum is by far the cheapest, it should form, in 
reference to this general action of the above sulphates, in all cases, the 
most economical application to the land. 

h. But they have each also their special action dependent partly upon 
their physical properties, and partly on their chemical constitution. 

Thus it will be of little use mixing any of them with the soil, unless 
they become capable of entering into the roots of the plants which are 
growing upon it. The facility with which this can be effected depends 
upon their solubility in water, which is very unlike. Thus an imperial 
gallon of pure water at the ordinary temperature will dissolve of 

Gypsum (burned,) f l^* 

Gypsum (unburned,) I lb. 

Sulphate of Potash, 1^ lbs. 

Sulphate of Soda, dry li lbs. 

Sulphate of Soda, crystallized 3i lbs. 

Sulphate of Magnesia 4 lbs. 

In rainy weather, therefore, and in moist climates, it would still be 
most economical to apply the gypsum, since, though very sparingly 

• See Appendijf. 



S31 SPECIAL ACTION UPON GRASSES AND CLOVERS. 

soluble, water would be sufficiently abundant to dissolve as much as the 
plant might require. But in times of only moderate rain, and especially 
in dry seasons, the use of the sulphates of soda and magnesia, .which 
are also low in price, is recommended by the comparative ease with 
which they may be talien up by water and conveyed to the roots. 

c. Again, the chemical constitution of these sulphates — the nature of 
the substance with which the sulphuric acid is combined — determines in 
a still greater degree the nature and extent of their special action. If 
the soil already abound in potash, in soda, in lime, or in magnesia, then 
the influence of these compounds may depend entirely upon the sul- 
phuric acid they contain. But suppose the land to be deficient in lime, 
then the gypsum we add will act not only in virtue of the sulphuric acid, 
but of the lime also which it contains, and thus its apparent effect will 
be much more striking, than when the land is naturally calcareous, or 
has been previously dressed with lime. So if it be deficient in potash, 
the sulphate of potash will be more efficient than it could be expected to 
prove upon a soil in which sulphuric acid alone is wanting. And so 
also, if lime and potash abound, and soda or magnesia be deficient, the 
sulphates of these latter bases will exercise a special action upon the 
soil, by supplying it at the same time with sulphuric acid and with soda 
or magnesia also. Thus on land to which lime has been abundantly 
added, according to the ordinary practice of husbandry, the sulphate of 
soda has the best chance of proving useful to vegetation, not only because 
it is more soluble, and is, therefore, more independent of the seasons, 
but because it is capable of supplying twodifierent substances — sulphuric 
acid and soda — neither of which are directly added in the ordinary 
manuring of the land, but both of which the plants may find difficulty 
in obtaining. 

d. Another consideration will indicate further special applications of 
these several sulphates, independent of the sulphuric acid which they 
in common contain. If we refer to the table (Lee. X., § 3,) in which is ex- 
hibited the constitution of the ash of the several clovers and grasses, we 
find the constituents of our sulphates to be present in 100 parts of the 
ash in the following proportions : — 

^y^^^;"^^^ Red Clover. ™J Lucerne. Sainfoin. 

Potash 8-81 19-95 31-05 13-40 20-57 

Soda 3-94 5-29 5-79 6-15 4-37 

Lime 7-34 27-80 23-48 48-31 21-95 

Magnesia .... 0-90 3-33 3-05 3-48 2-88 

Sulphuric Acid . . 3-53 4-47 3-53 4-04 3-41 

Of the two clovers the red contains more lime and much less potash, 
therefore the sulphate of lime is more likely to benefit the red clover, 
and the sulphate of potash the white, which is consistent with the re- 
sults of experiment. A similar difference exists between lucerne and 
sainfoin, to the former of which lime and soda are more necessary than 
the latter. The first column under rye grass shows, on the other hand, 
how very much smaller a proportion of all the four — potash, soda, 
lime, and magnesia — is required by this green crop than by the others ; 
and therefore that the same weight of any one of these sulphates, which, 
when applied as a top dressing to one crop (rye grass), would cause it to 



THEY AFFECT THE GROWTH OF THE STEM. 335 

thrive luxuriantly, may be insufficient to supply the most necessary 
wants of another crop (clover or sainfoin.) Not only the kind of mine- 
ral manure, therefore, which we mix with the soil, but the quantity also, 
must be determined by the kind of crop we intend to raise.* 

6°. Nitrates of Potash and Soda. — The efficacy ofthese two substances 
as manures in certain circumstances is now generally acknowledged, 
though the disappointments which have occasionally attended their use 
naturally cause the practical farmer to hesitate still, before he applies 
them in any quantity to his land. As these salts, especially the nitrate 
of soda, are comparatively abundant in nature, — as they are really be- 
neficial in many cases, and can be employed with a profit, — as their 
use in practical agriculture has recently excited considerable interest, — 
and as many experiments have in consequence been made with them 
upon various crops, — I shall briefly direct your attention to the most im- 
portant facts which have yet been established in regard to their action 
upon the growing plant. 

a. Apparent eff'ects of the Nitrates. — The first visible effect of the ni- 
trates upon every crop is to impart a dark green colour to the leaves and 
stems. 2°. They then hasten, increase, and not unfrequently prolong 
the growth of the plant. 3°. They frenerally cause an increase both 
in the weight of hay or straw, and of corn — though the colour and 
growth are occasionally affected without any sensible increase of the 
crop. 4°. The hay or grass produced is always more greedily eaten by 
the cattle than that which has not been dressed, even when the quantity 
is not affected; — but the grain is usually of inferior quality, bnnging a 
somewhat less price in the market, and yielding a smaller produce of 
flour. 

Its principal action seems to be expended in promoting the growth — 
that is, increasing the production of woody fibre, either in the stem or 
the ear, without so much affecting, except indirectly, the quantity of seed. 

Illustrations. — 1°. Mr. Pusey observed that the increase of his wheat 
crop, on the Oxford clay, where nitrate of soda was applied, arose from 
there being no underling straws with short ears as in the undressed, but 
all were of equal length and consequent fullness and ripeness. The 
nitrate had merely promoted the growth. 

2°. " It affected the tops of the potatoes, but the produce of bulbs 
was less both by weight and measure" (Mr. Grey, of Dilston). " On 
peas, in a thin sandy soil, subsoil gravel, it had much effect on the 
colour and strength of the stems, and on the state of forwardness, but 
when ripe, though the straw was stronger, there was no difference in the 
crop of peas" (Colonel Campbell, of Rozelle). " On land in high con- 
dition it did harm by forcing the straw at the expense of the ear" (Mr. 
Barclay). "It appeared to act strongly, and there was a greater bulk 
of straw, but the increase of grain was only 50 lbs. per acre" (Sir 
Robert Throckmorton). In another experiment of Mr. Barclay's the 
straw was very strong, and much of the wheat laid, but the undressed 
sold for 4s. a bushel more, and there was no profit. 

In all these cases the nitrate promoted chiefly the growth of the stem, 
or the production of woody fibre. The inferior quality of the grain and 

* For the theoretical opinions of other authora in regard to the action of gypsum, see 
the Appendix, No. VI. 



336 



EFFECTS UPON THE QUANTITY OF THE CROP. 



yield of flower was owing to this action. The grain was enveloped in 
a thicker covering of the woody matter which forms the skin or bran. 

3°. " The turnips after the nitrated wheat are decidedly hetievf the 
tops are still growing and luxuriant, while on the other part they are 
beginning to "fall" (Hon. H. Wilson). They seem, therefore, in some 
cases, at least, to prolong the growth. 

From the above statements we seem to derive an explanation why 
the effects of the nitrate should have been so universally observed upon 
the grasses and clovers — while in regard to its application to corn croj)s^ 
they indicate this important — 

Practical Rule. — Not to apply the nitrates upon land or under cir- 
cumstances where there is already a sufficient tendency to produce straw. 

b. Effects of the nitrates upon the quantity of the crop, — Cases have 
occurred where the nitrates have failed to produce any apparent effect 
at all — others where the colour was affected and the growth promoted 
without any ultimate increase of crop — and others again, where the ap- 
plication of these salts was decidedly injurious. These failures are de- 
serving of a close consideration, but let us first attend to the amount of 
benefit derived from their use where it has been attended with success. 



I. — Effect on Common and Clover Hay. 



Locality. 



PRODUCE PKR ACRE. 



Undressed. Dressed 



Quantity of Nitrate of Soda ap 
plied per acre, and nature of 
soil. 



Aske Hall, 
Earl of Zet and. 



At E 
Lord 



Erskine, i 

Blantyre. J 



Barochan, 
Mr. Fleming. 

Dilston, 

Mr. Grey. 

Farnhain, ^Suffolk, 

Mr. Muskett. 

Metliven Castle, 
Mr. Bishop. 



tons. cwt. 

2 12 

2 0^ 

2 1 

1 G 

2 11 
2 10 
2 4i 



tons. cwt. 

3 4 

3 Oi 

2 10 

2 4 

2 19^ 

3 18 
3 U 



1 cwt., on a thin light 
soil, subsoil clay upon 
limestone. 

120 lbs., good light soil, 
subsoil gravel. 

Ditto, clay soil on clay 
subsoil. 

160 lbs., stiff clay, after 
wheat. 

Ditto, light clay loam, 
drained, after barley. 

1 cwt., meadow hay, soil 
not mentioned. 

150 lbs., clover hay, soil 
not mentioned. 

1 cwt. nitrate of potash 
and 1^ of nitrate of so- 
da, had each the same 
effect on a heavy damp 
loam, partially drained. 



On the other hand, Mr. Barclay says that, on his heavy clay lands 
(plasiic clay), in Surrey, near the edge of the chalk, it is almost always 
a (ailurc ; and the Messrs. Drewitt, of Guildford, that on their chalk soils, 



EFFECT ON BARLEY AND OATS. 



337 



the additional produce of hay, whether on upland or meadow, does not 
repay the expense. 

II. — On Barley. 



Locality. 


PROD I CE. 


1 


ndressed. | Dressed. 


Quantity per acre, and kind of soil. 


grain. 


straw. 


gr 


straw, 
cwt. 

20-^ 
36 




Surrey, 
Mr. Barclay. 

Newton Hall, 

Northumberland, 

Mr. Jobling. 

Suffolk, 
Hon. H. Wilson. 


bush. 
44^ 

47 

18 


cwt. 

26 


bush. 
55a 

59 

32 


1 cwt. on light soil with chalk 
subsoil. 

1 cwt. on strong turnip land. 

1 cwt. on a poor sandy soil, 
where the turnips on the 
preceding year were nearly 
destroyed by the land blow- 
ing. 



In Berkshire, on the other hand, it failed (1839), for barley on the 
light lands, causing them in some ca.ses to be burned up (Mr. Pusey), 
but the season was droughty. 

III. — On Winter Rye. 

Mr. Fleming, of Barochan, applied 160 lbs. per acre to rye, upon a 
strong clay, after potatoes, and obtained — 

Undressed. Dressed. 

Grain ... 14 bushels 26 bushels. 

Straw . . . 1 ton 7i cwt 2 tons 19| cwt. 

IV. — Upon Oats. 



Locality. 


PRODUCE, 


Cluantity per acre 
and kind of soil. 


Undressed. 


Dressed. 


grain. 


straw. 


grain. 


straw. 


Bake well, 1 

Derbyshire, \ 

Mr. Greaves. ) 

Court Farms, ) 

Hayes, > 

Mr. Newman. ) 

Leatherhead, ) 

Surrey, > 

Mr. Barclay. ) 


bush. 
48i 

46 

40 


cwt. 
25f 

31 

61 


bush. 
64 

601 

60 


bush. 
38| 

461 
90 


1 cwt. ; heavy soil, 
clay subsoil, 

1 cwt, ; land saturat- 
ed with water, and 
out of condition. 

1 cwt. ; a loam con- 
taining flints, on a 
subsoil of chalk. 



Mr. Everett, in Norfolk, obtained an increase of 15 bushels per acre, 
by the use of f cwt. per acre ; and Mr. Calvert, of Ockley Court, of 
20 bushels of grain, and 9i cwt. of straw, by applying H cwt. of nitrate 
of soda. At Kirkleatham (North Yorkshire), it had an excellent effect 



338 



EFFECT OF THE NITRATES ON WHEAT. 



upon oats, on strong land — and on the strong clays of the Weald of Sur- 
rey and Sussex it is said by Mr. Dewdney, of Dorking, to be universally 
beneficial, particularly when sown on ley ground — paying the grower 
27s. to 30s. per acre. " When it has failed, the nitrate has been sown 
early, and when the land was in a dry state. In these instances the 
crop was more or less blighted." On the other hand, Mr. Barclay 
states that, on his strong heavy land (plastic clay), near the edge of the 
chalk, in Surrey, it gave no profit. 

In most cases, therefore, the nitrate of soda seems capable of produc- 
ing a large increase in the oat crop — the few failures which are noted 
must be due either to the state of the weather or to some peculiarities in 
the physical condition or chemical constitution of the soils on which they 
were observed. 

V. — On Wheat. 



PRODUCE. 



Locality. 



Undressed.! Dressed. 



grain straw grain straw 



FarnhaiTi, Suffolk, 
Mr. MvsJi-ctt, . 

Pciinswick, Glou 
cester,Mr. Ht/ett, 

Fiiirford Park, do. 

Mr. Raym. Barker, 

Mr. Dugdale, . 



Do 

Court Farm,Hayes 
3Ir. Nemnan, 
Brandon, SuiTolk, 
Hon. Mr. Wilson, 
Surrey, Mr. Bar- 
day, 

Faringdon, 
Mr. Pusey, 

Ocklcy Court, Mr. 

Calvert, . . . 
Newton Hall, Mr. 

Jobling, . . 
Cirencester, Dr. 

Daubeny, . . . 

Rozelle, near "Ayr, 
Col. Campbell, 



:| 



18i 
33i 

26 

42 

32 

14f 

27i 

30i 

33f 

31 

27 

211 

20^ 

33 

30 

27f 

35 



15 
34 

18* 



20 

24i 

24i 

20i 

20i 

251 

29i 
IG 



3U 



bushls 

27 
43i 

33i 

54 

36| 

20 

32 

36 

39i 

33i 

39 i 

26" 

244 

o 

451 

36 
31f 

27j 

47 
42 



21f 

38i 



251 



271 
341 
25i 
24i 

37f 

35i 
20i 
15i 

52 
76 



Quantity per acre, and kind of soil. 



\\ cwt. ; a poor spongy sandy soil. 

1 cwt. ; a stone-brash soil abounding in 
carbonate of lime. 

1 cwt. ; on a light stone-brash poor 
thin soil. 

1 cwt. nitrate of soda, on di gravelly soil ; 
an equal weight nitrate of potash, pro- 
duced only h bushel of increase C?). 

1 cwt. nitrate of soda on a strong clay. 
Both portions were previously limed. 

1 cwt.; on a veiy thin crop, injured by an 
unfavorable autumn. Soil not stated. 

I cwt.; on a fair light soil. 

Do., loamy, better land. 

1 cwt. ; soil loamy, resting on chalk, 
straw strong, and much wheat laid.* 

Do. on heavy soil, resting on the Ox- 
ford clay. But all these very different 
results were obtained in the samefidd. 

Do.; corn generally laid ; soil not men- 
tioned. 

1 cwt.; soil not mentioned. 
1 cwt. nitrate of potash. 
Do. nitrate of soda, soil and subsoil 
clay, resting on the corn-brash. 
180 ibs. nitrate of soda. 
Do. nitrate of potash. Soil not stated.t 



* The dressed grain sold at 4s. less than the undressed, and there was no profit ; the ni- 1 
trate failed on heavy land, and on land in high condition. 11 

t The produce of straw, especially from saltpetre, is vei-y surprising. It is stated at 518 
and 764 stones for the two lots respectively. I suppose the acres to be Scotch, and the 
stones 14 lbs. 



EFFECT UPON TURNIPS, AND THE QUALITY OF THE CROP. 339 

VI. — On Turnips. 

At Rozelle the Swedes were improved several tons an acre by the 
use of the nitrate of soda (Mr. Campbell). At Dorking it was very 
beneficial as a top-dressing to the Swedes and white turnips, wheu 
sown broad-cast at the rate of li cwt. per acre (Mr. Dewdney). lu 
neither of these cases is the soil described. On thin stony land upon 
chalk at Elmshurst, Bucks, turnips maniired with nitrate alone, were 
very superior to those to which 10 loads an acre of farm-yard manure 
had been applied (Mr. Burgess). The only numerical results with 
which I am acquainted are those of Mr. Barclay on a loamy soil resting 
on chalk. His crop of turnips was 

30-^ cwt. when dressed with bones and wood ashes, each 15 bushels. 

31 cwt. when dressed with 1 cwt. of nitrate of soda, drilled in. 

35 cwt. when seed and nitrate were both broad-cast. 

38 cwt. when the seed was drilled and the nitrate broad-cast. 
On the other hand, Lord Zetland thought it did no good to turnips; 
Mr. Vansittart, that on strong land well dunged it did harm ; and the 
Messrs. Drewitt, that on their dry rubbly chalk it had no effect on this 
crop, though it improved in a remarkable degree the succeeding crop of 
barley. 

We are obviously in want of more numerous and better observations, 
especially in regard to turnips. The above discordancies will either 
vanish when we obtain a larger collection of results, or they will find 
an explanation in the more accurate observations we may expect to 
obtain in regard to the climate, soil, and geological position of the 
locality in which each experiment is made. Those practical men who 
are really desirous of aiding the progress of scientific agriculture, — by 
which progress not only the national welfare, but their own individual 
interests also are likely to be promoted, — will do more towards this end 
by one single experiment in which weights and measures are carefully 
determined, and the soil, the climate, the geological position and the he 
of the land, accurately described, than by any number of mere general 
statements such as those I have here laid before you in regard to the 
effect of the nitrates upon the turnip crop. 

c. Effect of the nitrates on the quALiTY of the crop. — This I have 
already in some measure alluded to. It so affects the grass and clover 
as to make it more relished by the cattle. This is usually expressed by 
saying that the crop is sweeter, but since cattle are known to be fond of 
saline substances, it may be that the grasses are, by these salts, only 
rendered more savoury. It generally also gives a grain (of wheat) of 
an inferior quality — which has a thicker skin, and yields more bran. 
This may possibly arise from its having been generally allowed to ripen 
too long.* A question still undetermined is, whether the flour of 
nitrated corn is more nutritive than that obtained from corn which has 
been undressed. 

It is generally supposed that those samples of flour which contain 
the most gluten are also the most nutritive. But hitherto the only 
experiments which have been made with the view of determining the 
relative quantities of gluten in samples of grain from the same field, one 

* See Mr. John Hannam's valuable experiments on the orer-ripening of com in the 
Quarterly Journal of Agriculture. 

29 



340 AFTER-EFFECTS OF THE NITRATES. 

portion of which had been nitrated, and the other not, are, one made by |i 
Mr. Daubeny, and one reported by Mr. Hyett, to the latter of which 
I have already had occasion, for another purpose, to direct your 
attention.* 

In these experiments the flour of the several wheats gave — 

In Dr. Ddubeny's In Mr. Hyetl's 

Experiment. Experiment. 

Nitrated 15 per cent, of gluten . . . 23| per cent. 

Unnitrated .... 13 per cent, of gluten ... 19 percent. 

Excess of gluten in the } ^ ^^^^^^ ^j ^^^^^ 

nitrated 5> ' ^ * 

both of which results favour the supposition that one effect of the nitrates 
upon the quality of the grain is to increase the proportion of gluten, and 
thus to render them, as is generally believed, more nutritive. This is 
a result which theoretically we might be led to anticipate, were there 
no large increase in the quantity of the produce — for then we might 
naturally expect the nitrogen of the nitric acid to be expended solely in 
enriching the grain with gluten. But the increase of crop contains in 
many cases more nitrogen than we add to the soil when we dress it with 
one cwt. of nitrate of soda per acre ; there is, therefore, no excess of 
nitrogen which we can suppose to go to such an enriching of the more 
abundant crop of grain. For this reason, among others, I am inclined 
to doubt whether further careful examination will prove the flour from 
nitrated grain to be always richer in gluten, and, thereforer more nutri- 
tious. At all events increased experiments are to be wished for. 

d. After-ejects of these nitrates. — It is comparatively seldom that 
any good effects have been ob.served upon the crop which succeeds that 
to which the nitrate of soda has been applied. Where they have been 
noticed it has been chiefly in cases where from some cause (drought or 
dryness of soil chiefly) the salt has been prevented from exerting its 
full and legitimate action upon its first application. Thus, 

1°. Failing to improve turnips on a rubbly chalk soil, it greatl;y 
benefitted the succeeding crop of barley (Mr. Drewitt, Guildford, 
Surrey). 

Producing little effect on tares (upon a clay soil?) it improved 
rery much the turnip crop which followed (Mr. Barclay, Leatherhead, 
Surrey). 

2°. In the following instances the benefit was seen on successive 
crops : — 

After producing an increase of one-sixth in the wheat crop, both 
grain and straw, on a light sandy soil (6ub.>*oil ?), the turnips of the fol- 
lowing year were decidedly belter where the nitrate had been sown 
(Hon. H. Wilson, Brandon, Suffc)lk). 

After improving the crop of wheat, the after-crop of hay was also 
better (Mr. Grey, of Pilston.) 

At Upleatham, the second cut of clover was nearly as much im- 
proved as the first (Mr. Vansittart), and at Dili^ton the aftermath hay 
was greater in quantity, and better relished by the cattle (Mr. Grey). 

3°. A curious effect is noted by Mr. Rodvvell, of Alderton, Wood- 

* gee note, Lee. VIII., §8. 



THEIR ACTION AFFECTED BY CIRCU3ISTANCES. 341 

bridge— the white clover failed after barley on which nitrate had been 
used ! 

The solubility of these nitrates is so great that in our climate, in 
seasons of ordinary rain, and on lands having a moderate degree of 
inclination, we should expect that they would be in a great measure 
washed out of the land in a single year. Hence one reason — even 
supposing little of the salt to have entered into the roots of the growing 
crop — why we are not entitled generally to expect any marked effect 
from it upon a second crop. But let the season be so dry, or the soil 
so retentive, and the land so level, as to prevent its being all taken 
up by the roots, or washed away by the rains during one year, and we 
may then look for after-effects, such as those above described. 

c. Circumstances necessary to ensure the success of these saline 
manures. — This explanation will appear more satisfactory if we glance 
for a moment at the general conditions which are necessary to ensure 
the success of these or any other saline manures. 

1°. They must contain one or more substances which are necessary 
to the growth of the plant. 

2°. The soil must be more or less deficient in these substances. 

3®. The weather must prove so moist or the soil be so springy as to 
admit of their being dissolved, and conveyed to the roots. 

4°. They must not be applied in too large a quantity, or allowed to 
come in contact with the young shoots in too concentrated a form — the 
water that reaches the roots or young leaves must never be too strongly 
impregnated with the salt, or if the weather be dry, the plant will be 
blighted or burned up. 

5°. The soil must be sufficiently light to permit the salt easily to 
penetrate to the roots, and yet not so open as to allow it to be readily 
washed away by the rains. In reference to this point the nature of the 
subsoil is of much importance. A retentive subsoil will prevent the 
total escape of that which readily passes through a sandy or gravelly 
soil, while an open subsoil again will retain nothing that has once made 
its way through the surface. 

/. Cases in which the nitrates have failed. — A knowledge of the 
above conditions will enable us in many cases to explain why the 
nitrates, and other generally useful substances, have failed to exhibit 
any beneficial effect. 

1°. Thus on the light soils of Berkshire the nitrate of soda failed for 
barley, causing it often to be blighted or burned up. This, no doubt, 
arose from the drought which may act in one or other of several ways. 
Either it may prevent the salt from being dissolved at all, and thus hin- 
der its action altogether for the time, — or it may retard the solution till 
the plant has attained such a state of maturity, that it is no longer capa- 
ble of being equally benefitted by the introduction of the salt into its 
roots — or after being dissolved, and having partially descended into the 
soil, the drought may cause it to ascend again with the water which 
rises to the surface in consequence of the evaporation, and may thus 
present it to the plant in so concentrated a form as to injure the young 
shoots — or, finally, the action of the sun upon the green leaf, into which 
a portion of the salt has already been conveyed by the roots, may be so 
powerful as to concentrate the saline solution, or to increase its deconi- 



342 WHEN THE USE OF NITRATES IS BENEFICIAL. 

position to such an extent as to cause injury, and consequent blight to 
the leaf itself. 

2"^. Again, at Cheadale, in Clieshire (Mr. Austin), the nitrate of soda 
is said to have had a good effect on wheat and grass where the subsoil 
was clay^ but none where the subsoil was gravel, or the soil light and 
sandy. Here the supply of water in the soil may have been such as to 
fit it for entering readily into the roots in a proper state of dilution, when 
the retentive subsoil kept it within reach of the roofs, — and yet suffi- 
cient, at the same time, to wash it away altogether where the soil and 
subsoil were too open to be able to retard its passage. 

3°. But the occasional occurrence of droughts or the mere physical 
distinctions of lands as light or heavy, are not sufficient to account for 
all the recorded differences in the effect of the nitrates. Thus on the 
clays of the Weald in Sussex (Mr. Dewdney), and on the Oxford clay 
in Berkshire (Mr. Pusey), the use of the nitrate has been attended with 
general benefit upon oats and wheat, while on the plastic clay in Surrey 
(Mr. Barclay), it has been uniformly unsuccessful. The cause of these 
differences is to be sought for, most probably, in the chemical constitu- 
tion of the several clays, which are known to be very unlike. The 
Weald clay is a fresh water formation, contains much fine grained sili- 
ceous matter (Lee. IX., § 8), and is, therefore, comparatively pervious to 
water. The Oxford clay soils in Berkshire abound in lime, and must, 
therefore, be in some degree pervious, while the plastic clay of Surrey, 
where they are stiffest, contain little lime and partake more of the im- 
pervious character of pipe cla3'^s. It may possibly be in such differences 
as these that we are to find an explanation of the discordant results of 
different experimenters, but much further observation is still wanting 
before we can speak with any degree of confidence upon the subject. 

To some an explanation may appear to be most easily given by sup- 
posing the one soil to have been rich in soda, while the other was de- 
fective in this substance. I shall advert to this point in explaining the 
theory of the action of the nitrates of potash and soda. 

g. Circumstances in which the e7nployment of the nitrates is most bene- 
ficial. — 1°. It appears to succeed most invariably in lands which are 
poor — or out of condition — or on which the corn is thin. Every farmer 
knows that the most critical time with his crop, as with his cattle, is 
during the earliest stage of its growth. If it come away quickly and 
strong during the first few weeks, his hopes are justly high, but if it 
droop and linger after it is above the ground, his fears are as justly ex- 
cited. It is in this latter condition of things that an addition of nitrate 
comes to the aid of the feeble plant, re-animating the pining shoots, and 
making the thin corn tiller. On rich lands and thickly growing crops 
it only causes an over-growth of already abundant straw. According 
to the experiments of Mr. Barclay, it is most advantageous when sown 
broad-cast.* 

2°. Whatever may be the chemical nature of the surface soil, the 
success of the nitrate seems to be most sure where the land is not wholly 
destitute of water, where the soil is open enough to allow it readily to 

* A valuable precept also is, to proceed cautiously in the use of these expensive sub- 
fitances— making small trials at first, and increasing the quantities employed as success may 
warrant. By tliis mode of procedure large losses, of which I have heard, would have beea 
avoided. 



THEORY OF THE ACTION OF THE NITRATES. 343 

descend, and yet the subsoil sufficiently retentive to prevent it from 
being readily washed away. 

3°. I throw it out as a suggestion which has occurred to me from a 
comparison of the results contained in the above tables, with the kind 
of soils on which the experiments were made — that probably the pre- 
sence of lime in the soil may tend to insure the success of the nitrate. 
In many of the instances of large crops obtained by its aid the land was 
either naturally rich in lime, or it had, in the ordinary course of hus- 
bandry, been previously marled or limed. 

h. Theory of the action of the nitrates. — The nitric acid of these salts 
contains 26 per cent, of its weight of nitrogen — or one cwt. of pure dry 
nitrate of soda contains about 19 lbs. of nitrogen. This nitrogen we 
know to be a necessary constituent of plants — one which they obtain 
ahnost wholly from the'soil — but which nevertheless is generally present 
in the soil in small quantity only. We have already seen reason (Lee. 
VIII. , § 5), to believe that nitric acid exists naturally in the soil, and is the 
form in which a large portion of their nitrogen is conveyed into the roots 
of plants; — when we add it to our fields, therefore, we only aid nature 
in supplying a compound by which vegetables are usually sustained. 
And as the young plant will necessarily languish in the absence of one 
essential kind of food, although every other kind it may require be pre- 
sent in abundance, it is easy to see how the growth of a crop — languidly 
proceeding upon a soil deficient in nitrogen — may be suddenly re-ani- 
mated by an application of nitrate of soda to its roots. That this is the 
true way in which the nitrates generally act is supported by the observa- 
tion that it is in the poorest soils that they are most useful to the husband- 
man. 

We have already seen also, that one function of the leaf in the pre- 
sence of the sun is to decompose carbonic acid, and give off its oxygen 
(Lee. v., § 5). It exerts a similar action upon the Jiitric acid of the 
nitrates, and upon the sulphuric acid of the sulphates, discharging their 
oxygen into the air, and thus leaving the nitrogen and sulphur at liberty 
to unite with the other elementary substances contained in the sap — for 
the production of the several compounds of which the parts of the grow- 
ing plant consist. 

Nor, as shewn in a previous lecture, (VIII., § 8,) is the good effect of 
these nitrates upon the crop limited to the supply of that quantity of 
nitrogen only which they themselves contain. The excess of crop 
raised by their aid often contains very much more nitrogen than they 
have been the means of conveying to the roots — even supposing it all 
to have been absorbed and appropriated by the plant. This arises from 
the circumstance that the more the plant is made to thrive, the more nu- 
merous and extended become its roots also, and these roots are thus 
enabled to gather from the deeper and more distant soil those supplies 
of nitrogenous and other necessary food, which would have remained 
beyond their reach had the plant been allowed to remain in its pre- 
viously feeble or more languid condition. This has been called the 
Stimulating effect of manures, and some substances have been said to 
act only in this way upon vegetation. This, however, appears to me to 
be a mistake. The supposed stimulating is alv/ays a secondary effect, 
and necessarilv follows from the use of every kind of manure, which by 
29* 



344 COMPARATIVE EFFECTS OF THESE TWO JSITRATES. 

feeding the plant gives it greater strength, and thus enables it to appro- 
priate Other supplies of food which were previously beyond its reach, or 
which from the absence of one necessary constituent it could not render 
available lo its natural growth. 

In this way the nitrates act as such — in contra-dislinction lo the sul- 
phates and other salts of potash and soda. But there is every reason to 
believe that the potash and soda themselves often aid the effect of the 
nitric acid with which they are associated. In soils deficient in these 
alkalies tlie nitrates would act b3neficially, even though nitric acid were 
already j)resent in abundance, — while, on the other hand, a field that is 
defective in both constituents of the salt (nitric acid and potash or soda), | 
■will be more grateful for the same addition of it than one in which either » 
of them already abounds. In this way, it is not unlikely that the dis- 
cordant results of experiments, even on the same farm, and especially 
when the soils are different, may occasionally be explained. 

i. Special effects of the nitrates of potash andsoda. — On this alkaline 
constituent of the two nitrates will depend the siJecial action of each 
when applied to the same soil under the same circumstances. It has 
not yet been clearly made out that any definite special action can be 
ascribed to them, yet some experiments bearing upon this point have 
already been published, to which it will be proper to advert. From the 
study of the special action of given manures upon given crops, practical 
agriculture has much good to expect. 

1°. At Rozelle, near Ayr (1840), nitrate of potash caused oats to 
come away darker and stronger, and give a heavy crop, while in the 
same field nitrate of soda produced no benefit. The soil was inferior, 
light, and sandy, with a red irony subsoil (Capt. Hamilton). It is added 
that the crop was injured by the early drought, from which it'never re- 
covered. This fact renders the special eflTect of the nitrate of potash in 
this case doubtful. 

2°. In the experiments upon wheat, made by the same gentleman 
on the same farm, — it is to be presumed upon a similar soil. 

Nitrate of soda gave . . 46 bush, grain, and 52 cwt. straw ; 

Nitrate of potash gave. . 42 bush, grain, and 76 cwt. straw; 

the produce of straw being here also greatly in favour of the potash salt. 

3°. Dr. Daubeny also, in the experiment upon wheat above detailed, 
found the nitrate of potash to increase the produce considerably while 
the nitrate of soda caused no increase whatever. The soil was stiff clay 
upon the corn-brash. 

These superior effects of the potash salt may certainly be ascribed to 
the greater deficiency of the several soils in potash than in soda, a sup- 
position which in the case of the Rozelle experiment is consistent with 
the fact, that common salt, when tried upon the same land, produced no 
good effect. If however, as some suppose, (p. 328), potash and soda are 
capable of rc-placing each otlier in the living vegetable without materi- 
ally affjcting its growth, this explanation cannot be the true one. Fur- 
ther experiments, however, if carefully conducted, will not fail to clear 
up this question. 

4°. On a gravelly soil Mr. Dugdale obtained an increase of 12 bushels 
of wheat by the use of nitrate of soda, while nitrate of potash increased 
the crop by only half a bushel. 



USE OF COMMON SALT AS A 3IAMTRE. 



345 



This result may be explained after the same manner as the preceding 
— the soil may have already abounded in potash. 

5°. In Perthshire, upon a moist loam, Mr. Bishop obtained an equal 
increase of hay from the use of both nitrates ; each having caused the 
production of a double crop. 

The equality in this case may have risen from the effects being wholly 
due to the nitric acid, both potash and soda being already abundant in 
the soil. This is consistent with the situation of the locality in a granite 
country, and is further supported by the fact, that on the same soil and 
field, ammoniacal liquor, which contains no alkali, produced a still larger 
increase of produce. 

You will understand, however, that all these attempted explanations 
proceed upon the supposition that the experiments have been both care- 
fully made and faithfully recorded. 

7"^. Chloride of Sodium or Common Salt. — The use of common salt as 
a manure has been long recommended. In some districts it has been 
highly esteemed, and is still extensively and profitabl}'^ applied to the land. 
It has, like many other substances, however, suffered in general estima- 
tion from the unqualified terms in which its merits have been occa- 
sionally extolled. About a century ago (1748), Brownrigg* maintained 
that the whole kingdom might be enriched by the application of com- 
mon salt to the soil, and since his time its use has been at intervals 
recommended in terms of almost equal praise. But these warm recom- 
mendations have led sanguine men to make large trials, which have occa- 
sionally ended in disappointment, and hence the use of salt has repeat- 
edly fallen into undeserved neglect. 

It is certain that common salt has in very many cases been advanta- 
geous to the growing crop. Some of the more carefully observed results 
which have hitherto been published, are contained in the following table : 



Locality. 



UPON ■WHEAT. 



Mr, G. Sinclair. 



Great Totham,Essex. i 

Mr. Cuth. Johnson. \ 

Barochan, Paisley, i 

Mr. F^lemins. \ 



ON BARLEY. 

Suffolk, Mr. Ransom. 



ON HAY. 

At Aske Hall, near 

Richmond. 

At Erskine, near 

Renfrew. 



Produce 


)er acre 


Unsalted 


Salted. 


bushels. 


bushels 


16i 


22i 


Hi 


21 


16 


I7f 


— 


23i 


12 


28i 


— 


28f 


\u 


261 


25 


32 


30 


51 


tons.cwt. 


ton.cwt. 


2 10 


3 12 


2 


2 12 


2 1 


2 8 



- Quantity applied per acre, and kind of soil. 



11 bushels, after barley. 

6^ do., after beans. 

Do. sown with the seed, ) after 

Do. dug in with the seed, \ peas. 

5 i do. applied before sowing, ) after 

lido., do., do, ^turnips. 

5 bushels, light gravelly soil. 

160 lbs., heavy loam, after potatoes. 



16 bushels. 



6 bushels, tliin light soil, clay sub- 
soil, 

5 bushels, light soil on gravel. 
Do., clay soil on clay. 



* On the art of making common salt, p. 158 (London, 1748), 



346 CAUSES OF THE FAILURE OF COMMON SALT 

But it is as certain that in many cases, when applied to the land, com- 
mon salt has failed to produce any sensible improvement of the growing 
crop. And as failures are long remembered, and more generally made 
known than successful experiments, the fact of their frecjuent occurrence 
lias prevented the use of salt in many cases where it might have been 
the means of much good. 

Causa of these failures. — It is not, indeed, to be wondered at, that 
amid conflicting statements as to its value, the practical farmer should 
have hesitated to incur the trouble and expense of applying it — so long 
as no principle was made known to him by which its application to this 
soil rather than to that, and in this rather than the other locality, was to 
be regulated. 

1°. We know that plants require for their sustenance and growth a 
certainsupi)ly of each of the ronsiitucnts of common salt, which supply, 
in general, they must obtain from the soil. If the poil in any field con- 
taiti naturally a sufficient quantity of common salt — or of chlorine and 
soda, in any other state of combination — it will be unnecessary to add 
this substance, or, if added, it will produce no beneficial effect. Jf, od 
the other hand, the soil contain little, and has no natural source of sup- 
ply, the addition of salt may cause a considerable increase in the crop. 

Now there are certain localities in which we can say beforehand that 
common salt is likely to be abundant in the soil. Such are the lands 
that lie along the sea coast, or which are exposed to the action of pre- 
vailing sea winds. Over such districts the spray of the sea is constant- 
ly borne by the winds and strewed upon the land, or is lifted high in the 
air, from which it descends afterwards in the rains.* This consideration, 
therefore, affords us the important practical rule in regard to the appli- 
cation of common salt — that it is most likely to be hemficialin spots which 
are remote from the sea or are sheltered from the prevailing sea winds. 

It is an interesting confirmation of this practical rule, that nearly all 
the successful experiments above detailed were made in localities more 
or less remote from the sea, while most of the failures on record were 
experienced near the coast. This consideration, it may be hoped, 
will induce many practical men to proceed with more confidence in 
making trial of its effects on inland situations. It is very desirable that 
the value of this practical rule, which I suggested to you in a former 
lecture (Lee. IX., § 4.), should be put to a rigorous test.f 

2°. But some plants are more likely to be benefitted by the applica- 
tion of common salt than others. This may be inferred from the fact 
that certain species are known to flourish by the sea-shore, and where 
they grow inland to select such soils only as are naturally impregnated 
with much saline matter. Observations are still wanting to show which 

* Dr. Madden has calculated that the quantity of rain which falls at Penicuick in a year, 
brings down upon each acre of land in that neighborhood more than 600 lbs. weight of 
common salt. This would be an enormous dressing were it all to remain upon the land, 
llf-avy rains, however, probably carry otF more from the soil than they impart to it. It is 
the gentle sljowers that most enrich the fields with the saline and other matters they con- 
tain. 

1 A number of failwres are described in the sixth volume of the " Transactions of the 
Highland and Agricultural Society." Dr. Madden has recently shown that to nearly ail 
these cases the above principle applies — the farms on which they were tried being more or 
less freely exposed to the winds from the east or west sea. — Quarterly Jour7iul of Agricul- 
ture, Sept. 1812, p. 574. 



WHEN APPLIED AS A MANURE. 347 

of our cultivated crops is most favoured by common salt. It is known, 
however, that the grass of salt marshes is peculiarly nourishing, and is 
much relished by cattle, and that the grass lands along various parts of 
our coast produce a herbage which possesses similar properties. It is 
said also that the long tussack ^rass which covers the Falkland Islands, 
luxuriates most when it is within the immediate reach of the driving 
spray of the southern sea. It may well be, therefore, that among our 
cultivated crops one may delight more in common salt than another,— 
and if we consider how much alkaline matter is contained in the tops 
and bulbs of the turnip and the potatoe, we are almost justified in con- 
cluding that generally common salt will benefit green crops more than 
crops of corn, and that it will promote more the development of the 
leaf and stem than the filling of the ear. 

If this be so, we can readily understand how a soil may already con- 
tain abundance of salt to supply with ease the wants of one crop, and 
yet too little to meet readily the demands of another crop. The appli- 
cation of salt to such a soil will prove a failure or otherwise, according 
to the kind of crop we wish to raise. 

3°. Failures have sometimes been experienced also on repeating the 
application of salt to fields on which its first effects were very favour- 
able. In such cases it may be presumed that the land has been already 
supplied with salt, sufficient perhaps for many years' consumption,— 
and that it now requires the application of some other substance. 

If it be desired, experimentally, to ascertain whether the land already 
contains a sufficient supply of common salt, the readiest method is to 
collect half a pound of the soil in dry weather, to wash it well with a pint 
or two of cold distilled water, and then to filter through paper, or care- 
fully to pour off the clear liquid after the whole of the soil has been al- 
lowed to subside. A solution of nitrate of silver (common lunar-caus- 
tic of the shops) will throw down a white precipitate, becoming purple 
in the sun, which will be more or less copious according to the quantity 
of salt in the soil. If this precipitate be collected, dried in an oven, 
and weighed, every 10 grains will indicate very nearly the presence of 
4 grains of common salt. The quantity of this precipitate to be expect- 
ed, even from a soil rich in common salt, is, however, very small. If 
half a pound of the dry soil yield a single grain of salt, an acre should 
contain about 1000 lbs. of salt where the soil is 12 inches deep — where it 
has a depth of only 6 inches it will contain nearly 500 lbs. in every acre. 

8°. Chlorides of Calcium and Magnesium. — These compounds are 
rejected in large quantities as a refuse in some of our chemical manu- 
factories — and they are contained, especially the latter, in considerable 
abundance in the refuse liquor of our salt pans. They have both been 
shown to be useful to vegetation (see Appendix), and where they are 
easily to be obtained, they are deserving of further trials. Like com- 
mon salt, it is generally in inland situations that they are fitted to be 
the most useful. Where salt springs are found in the interior of Ger- 
many, the refuse obtained by boiling down the mother liquors after the 
separation of the salt has been often applied with advantage to the land. 

Theory of the action of these chlorides. — Common salt and the chlo- 
rides of calcium are not unfrequently found in the sap of plants — they 
may be supposed, therefore, to enter into the roots without necessarily 



348 PHOSPHATE OF I IME AND EARTH OF BONES. 

undergoing any previous decomposition. But we have already seen (Lec.l 
v., § 5), iliat the green leaves under the influence of the sun, have the 
power of decomposing common salt — and no doubt the other chlorides' 
also— and of giving off their chlorine into the surrounding air. When 
they have been introduced into the sap therefore, by the roots, the plant 
first appropriates so much of the chlorine they contain as is necessary 
for the supply of its natural wants, and evolves the rest. When common 
salt is thus decomposed, soda remains behind in the sap, and this is 
either worked up into the substance of the plant, or performs one or 
other of those indirect functions 1 have already explained to you (p. 328) 
when illustrating the probable action of potash and soda upon the verre- 
table economy. When the other chlorides (of calcium or magnesium) 
are decomposed, lime or magnesia remains in the sap, and is in like 
manner either used up directly in the formation of the young stem and 
seed, or is employed indirectly in promoting the chemical changes that 
are continually going on in the sap. The living plant, when in a healthy 
state, 18 probably endowed with the power of admitting into its circula- 
tion, and of then decomposing and retaining, so much only of these 
several chlorides, or of their constituents, as is fitted to enable its several 
organs to perform their functions in the most perfect manner. 

In the soil itself, in the presence of organic matter of animal and 
vegetable origin, common salt is fitted to promote certain chemical 
changes, such as the production of alkaline nitrates— and probably sili- 
cates—by which the growth of various kinds of plants is in a greater or 
less degree increased. In the soil, also, ilom their tendency to deli- 
quesce, or run into a liquid, all these chlorides attract water from the air, 
and thus help to keep the soil in a raoister state. When applied in 
sufficient quantity tiiey destroy both animal and vegetable life, and 
have, in consequence, been often used with advantage for the extir- 
l)aiion of weeds, and for the destruction of grubs and other vermin that 
infest the land. 

^ 9°. Phosphate of Lime and Earth of Bones.^The cattle that graze 
in our fields derive, as you know, all the earthy materials of which cer- 
tam parts of their bodies consist from the vegetables on which they feed. 
These vegetables again must derive them from the soil. Thus the earth 
of bones, or the phosphoric acid and Hme of which it consists (Lee. IX., 
§ 4), must exist in the soil on which nutritive plants grow, and it must 
occasionally occur that a soil will be deficient in these substances, and 
will, therefore, supply them with difficulty to the crops it rears. The bene- 
fit which in this country is so often experienced from the use of bones as a 
manure, has been ascribed, in jjart, to the supply of bone-earth, with 
which It enriches the land.* It is not, however, to be inferred from this, 
that wherever bones are useful, the application of bone-earth alone— in the 
form of burned bones, or of the native phosphate of lime (Lee. IX. § 4 ) 
will necessarily prove advantageous also. Burned bones were former- 
ly employed in England, but the practice has gradually fallen into dis- 
use, and the same is, I believe, the case in Germany. This is no proof 
however, that the native phosphate of Estremadura— already, it is said 
imported into Ireland for agricultural purposes,— would not benefit many 

* See Appendix, No I. * 



USE OF SULPHATE OF AMMONIA. 349 

soils if applied in the state of a safficiently fine powder. Until carefully 
conducted experiments, however, shall have been made, and the nume- 
rical results precisely ascertained, it would be improper to incur much 
risk either in bringing this substance to our shores or in applying it to 
our fields. 

10°. Silicates of Potash and Soda. — These compounds, which have 
been already described (Lee. X., § 1), are supposed to act an important 
part in the growth of the grasses, and of the corn-bearing plants, by sup- 
plying, in a soluble state to the roots, the silica which is so necessary 
to the strength of their stems. This supposition has been strengthened 
by the results of some experiments made by Lampadius, who found a 
solution of silicate of potash to produce remarkable effects upon Indian 
corn and upon rye.* It is possible to manufacture them at a cheap rate, 
and it would be desirable to ascertain b}'^ further trials how far the em- 
ployment of these compounds, as artificial manures, can be safely re- 
commended or adopted with the hope of remuneration.f 

11°. Salts of Ammonia. — There is reason to believe that ammonia in 
every state of combination is fitted, in a greater or less degree, to pro- 
mote the growth of cultivated plants. None of its compounds, how- 
ever, are known to occur any where in nature in such quantity as to be 
directly available in practical agriculture, and only a very few can be 
produced by art at so low a price as to admit of their being used with 
profit. 

a. Sulphate of Ammonia. — An impure sulphate is manufactured by 
adding sulphuric acid to fermented urine, or to the ammoniacal liquor 
of the gas works, and evaporating to dryness. When prepared fmm 
urine, it contains a mixture of those phosphates which exist in urine, 
and which ought to render it more valuable as a manure. The gas 
liquor yields a sulphate which is blackened by coal tar — a substance 
which, while not injurious to vegetation, is said to be noxious to the 
insects that infest our corn fields. In any of these economical forms this 
salt has been found to promote vegetation; but accurate experiments 
are yet wanting to show in what way it acts — whether in promoting the 
growth of the green parts or in filling the ear, or in both — to what kind 
of crops it may be applied with the greatest advantage — and what 
amount of increase may be expected from the application of a given 
weight of the salt. It is from the rigorous determination of such points 
that the practical farmer will be able to deduce the soundest practical 
precepts, and at the same time to assist most in the advancement of 
theoretical agriculture. 

The crystallized sulphate of ammonia is soluble in its own weight of 
water. 100 lbs. contain about 35 lbs. of ammonia, 53 lbs. of acid, and 
12 lbs. of water. It may be applied at the rate of from 30 lbs. to 60 lbs. 
per acre. 

b. Sal-Ammoniac or Muriate of Ammonia. — This salt, in the pure 
state in which it is sold in the shops, is too high in price to be economi- 
cally employed by the practical farmer. An impure salt might, how- 

• Lehre von den mineralischen Dunginitleln, p. 25 (1833). 

t I have been informerl by Dr. Play fair that a number of experiments with a soluble 
silicate of soila, manufactured at Manchester, have this summer (1842) been made at his 
suggestion, the results of which will, no doubt, prove very interesting. 



350 SAL-AMMONIAC AND CARBONATE OF AMMONIA. 

ever, be prepared from the gas liquor, which could be sold at a sufficiently f 
cheap rate to admit of an extensive application to the land.* The only 
numerical results from the use of this salt with which I am acquainted, 
are those given by Mr. Fleming, who applied it at the rate of 20 lbs. i 
per acre to wheat on a heavy loam, and to winter rye, on a tilly clay, ■ 
both after potatoes, and obtained the following increase of produce per 



acre 



Rye, undressed . 
Do. dressed . . 


Grain. 
14 bushels. 
19 do. 


each 
each 


Straw. 
36i CWt. 
43^ do. 


Increase . . . 

Wheat, undressed 

Do. dressed . 


5 bushels. 
25 bushels, 
26^ bushels. 


7 CWt. 

61 lbs. 

62 lbs. 


Increase . . . 


Ij bushels. 





I 



The increase of these experiments was not very large, but the quan- 
tity of sal-ammoniac employed was probably not great enough to pro- 
duce a decided effect. Itis a valuable fact for the farmer, however, and 
not uninteresting in a theoretical point of view, that a part of the same 
wheat field, dressed with Ih cwt. of common salt per acre, gave a prO' 
duce of 40 bushels of grain (see Appendix, No. II.) 

c. Carbonate of Ammonia — is obtained in an impure form by the dis- 
tillation of horns, hoofs, and even bones. In this impure form it is not 
generally brought into the market, but in this state it might possibly be 
afforded at so low a price as to place it within the reach of the practical 
farmer. It is supposed by some that this carbonate is too volatile — or 
rises too readily in the form of vapour — to be economically applied to 
the land. In the form of a weak solution, however, put on by a water 
cart, or in moist showery weather simply as a top-dressing, especially 
to grass lands and on light soils, it may be safely recommended where 
it can be cheaply procured. 

d. Ammoniacal Liquor. — This is proved by the success which has in 
many localities been found to attend the application of the ammoniacal 
liquor of the gas works. This liquid holds in solution a variable quan- 
tity of sulphate of ammonia and of sal-ammoniac, f but in general it is 
richest in the carbonate of ammonia. 

The strength of the liquor varies in different gas works; chiefly ac- 
cording to the kind of coal employed for the manufacture of the gas. 
One hundred gallons may contain from 20 lbs. to 40 lbs. of ammonia, 
in one or other of the above states of combination. No precise rule, 
therefore, can be given for the quantity which ought to be applied to the 
acre of land, but as the application of a larger quantity can do no harm, 
provided it be sufficiently diluted with water, one hundred gallons may 
be safely put on at first, and more if experience should afterwards prove 
it to be useful. 

On grass and clover, upon a heavy moist loam, Mr. Bishop applied 

• By mixing, for example, the waste muriatic acid, or the waste chloride of calcium, with 
gas liquor, and evaporating the mixture to dryness. 

t Each gallon of the ammoniacal liquor of the Manchester gas-works is said to contain 2 
ounces of Sal- Ammoniac. In these works the Cannel ccal of Wigan is employed. 



SPECIAI, ACTION OF THE SULPHATE AND NITRATE. 351 

105 gallons an acre, diluted with 500 gallons of water, and obtained, of 
hay, from the 

Undressed ... | lb. per square yard, or 20^ cwt. per acre. 

Dressed .... li lb. do. or 61* cwt. do. 



Increase ... 1 lb. do. or 41 cwt.* do. 

The increase here is so very great that further trials with this li(|uor — 
hitherto, in most country towns at least, allowed to run to waste — cannot 
be too strongly recommended. On the dressed part, according to Mr. 
Bisbop, the Timothy grass was particularly luxuriant. 

These experiments with the gas liquor show, as I have said, that im- 
pure carbonate of ammonia may be safely apphed to the land without 
any previous preparation. If it is wished, however, to fix it or to ren- 
der it less volatile — which in warm and dry seasons may sometimes be 
desirable — this may be effected by mixing it with powdered gypsum, in 
the proportion of 1 lb. to each gallon of the ammoniacal liquor, or by 
adding directly sulphuric acid, or the waste of muriatic acid of the al- 
kali works. f 

e. Nitrate of Ammonia. — If it be correct that those substances act 
most powerfully as manures which are capable of yielding the largest 
quantity of nitrogen to plants, the nitrate of ammonia ought to promote 
vegetation in a greater degree than almost any other saline substance we 
could employ. According to the experiments of Sir H. Davy,} how- 
ever, this does not appear to be the case, though Sprengel has found 
it more efficacious than the nitrates either of potash or of soda. This 
question as to the relative action of the nitrate of ammonia is very in- 
teresting theoretically, but it directly concerns practical agriculture very 
little, since the high price of this salt is likely to prevent its being ever 
employed in the ordinary operations of husbandry. 

f. Special action of the different Salts of Ammonia. — The theory of 
the action of ammonia itself upon vegetation I have in a former lecture 
(Lee. VIII., § 6) endeavoured to explain to you. But the special action of 
the several saline compounds of ammonia above described will depend 
upon the qualities of the acid with which it may be in combination. 

The sulphate will partake of the action of the sulphates of potash, 
soda, or lime (gypsum), — in so far as it may be expected to exhibit a more 
marked effect upon the leguminous than upon the corn crops, and upon 
the produce of grain than on the growth of the leaves and the stem. 
This special action may be anticipated from the sulphuric acid it con- 
tains. And if this reasoning from analogy be correct, we should expect 
the sulphate of ammonia to rank among the most useful of manures — 
since the one constituent (ammonia) will promote the general growth of 
the plant, while the other will expend its influence more in the filling 
of the ear. 

The nitrate again has been found to act more upon the crops of corn 
than upon thelegumiuous plants and clovers (Sprengel) — a result which 

* Prize Essays of the Highland Society, xiv., p. 359. 

1 100 gallons thus saturated with acid will convey to the soil about 100 lbs. of sulphate of 
ammonia or of sal-ammoniac. 

t Davy's Agricultural Chemistry, Lecture Yll. 
30 



352 MIXTURE OF NITRATE WITH SULPHATE OF SODA. 

is to be explained by the absence of sulphuric acid, which appears tdii 
aid especially in the development of the latter class of plants. 

On this subject, however, experiments are too limited in number, 
in general too inaccurately made, and our information in consequence 
too scanty to enable us as yet to arrive at satisfactory conclusions. 

12°. Mixed Saline Manures. — The principle already so frequently 
illustrated, that plants require for their rapid and perfect development a 
sufficient supply of a considerable number of different inorganic sub- 
stances, will naturally suggest to you that in our endeavours to render a 
soil productive, or to increase its fertility, we are more likely to succeed 
if we add to it a mixture of several of those substances, than if we dress 
it or mix it up with one of them only. This theoretical conclusion is 
confirmed by universal experience. 

Nearly all the natural inanures, whether animal or vegetable, which 
are appHed to the land, contain a mixture of saline substances, each of 
which exercises its special effect upon the after-crop — so that the final 
increase of produce obtained by the aid of these manures, must be as- 
cribed not to the single action of one of their constituents, but to the joint 
action of all. An important practical problem, therefore, propounded 
by scientific agriculture in its present state, is — what mixtures of saline 
eubstances are most likely to be generally useful, what others specially 
useful to this or to that crop? The complete solution of this problem 
will require the joint aid of chemical theory and of agricultural experi- 
ment,— of experiments often varied and probably long continued. But 
that we may finally expect to solve it, will appear from what has al- 
ready been accurately observed in regard to the effect of certain artifi- 
cial mixtures upon some of our cultivated crops. Thus — 

a. Mixture of Nitrate with Sulphate of Soda. — If, instead of dressing 
young potatoes with nitrate or with sulphate of soda alone (page 331), 
we employ a mixture of the two, the growth of the plant is much more 
promoted and the crop of potatoes much more largely increased. Thus 
Mr. Fleming (in 1841) applied to his potato crop a mixture of equal 
weights of nitrate and of dry sulphate of soda in the proportion of 200 
lbs. of the mixture to the imperial acre, with the following remarkable 
result : — 

Undressed, . , . Q6 bolls, each 5 cwt., per acre. 
Dressed, . . . .107 bolls. 

Increase, . . . 41 bolls,* or 10 tons per acre ! 

The stems also were six and seven feet high. The addition of nitrate 
of soda to a portion of the same field gave a produce of only 80 bolls. 
Similar effects, of which, however, I have not yet obtained the numeri- 
cal results, have been observed on the same crop in various localities 
during the present season (1842). 

The effect of this one artificial mixture holds out the promise of much 
good hereafter to be obtained by the judicious trial of other mixtures — 
probably of a greater number of substances — upon all the crops we are 
in the habit of raising for food. 

h. Wood ashes. — This opinion is strengthened by the effects which 

* See Appendix, No. HI. 



COMPOSITION OF WOOD ASHES, AND USE AS A MANURE. 353 

have almost universally been found to follow the use of wood ashes and 
of the ash of other vegetables in t[ie cultivation of the land. 

The quality of the ash left by plants when burned varies, as we have 
already had occasion to remark (Lee. X., § 4), with a variety of circum- 
stances. It always consists, however, of a mixture in variable propor- 
tions of carbonates, silicates, sulphates, and phosphates of potash, soda, 
lime, and magnesia, with certain other substances present in smaller 
quantity, yet rriore or less necessary, it may be presumed, to vegetable 
growth. Thus, according to Sprengel, the ash of the red beech, the oak, 
and the Scotch fir {pinus sylvestris), consists of 

Tj ^ Tj I rv K Scotch Pitch Pine. 

Red Beech. Oak. pj^. (Berihier) 

Silica 5-52 26-95 659 750 

Alumina 233 

Oxide of I-on 3 77 814 1703 1110 

Oxide of Manganese . . 3-85 — ' ' — 2-75 

Lime 2500 1738 23-18 1360 

Magnesia 500 1-44 5 02 435 

Potash 2211 16-20 220 1410 

Soda 3-32 6-73 222 2075 

Sulphuric Acid .... 7-64 3-36 223 3-45 

Phosphoric Acid .... 562 1-92 275 0-90 

Chlorine 184 241 2-30 

Carbonic Acid 1400 1547 36-48 1750 

100 100 100 960 

The composition of these different kinds of ash is very unlike — that 
of the pitch pine, for example, being greatly richer in potash and soda» 
and poorer in lime and phosphoric acid, than that of the Scotch fir — 
while the beech is richer than any of the others in potash and litrie and 
in the sulphuric and phosphoric acids. The several effects of different 
kinds of wood ashes when applied to the land will therefore be different also. 

In this country wood ashes are largely employed in many districts, 
mixed with bone dust, as a^manure for turnips, and often with great 
success. As much as 15 bushels {7^ cwt.) of ashes are drilled in per 
acre with 15 bushels (6 cwt.) of bones. The large quantity of alkali 
present in the turnip crop {Lee. X., § 3) may be supposed to explain 
the good effects which wood ashes have upon it, and may lead us to ex- 
pect that they would in a similar degree increase the produce of the 
carrot and of the potatoe.* 

The immediate hene^toH wood ash is said to be most perceptible upon 
leguminous plants (Sprengel) such as lucerne, clover, peas, beans, and 
vetches. As a top-dressing to grass lands it roots out the moss and pro. 
motes the growth of white clover. Upon red clover its effects will be 
more certain if previously mixed with one fourth of its weight of gyp- 
sum. In small doses of two or three hundred weight (4 to 6 bushels) 
it may be safely applied even to poor and thin soils, but in large and 
repeated doses its effects will be too exhausting unless the soil be either 
naturally rich in vegetable matter, or be mixed from year to year with 
a sufficient quantity of animal or vegetable manure. 

• This inference has been verified by Mr. Wharton, of Drybnrn, who ha? obtained an ex- 
cellent crop of potatoes from newly ploughcd-out land by manuring with wood ashes only. 



354 SPONTANEOUS COMBUSTION OF WOOD ASHES. 



I 



In so far as the immediate effect of wood ashes is dependent upon 
the soluble saline matter they contain, their effect may be imitated by 
a mixture of crude potash with carbonate and sulphate of soda, and a 
little common salt. The wood ash of this country contains only about 
one-fifteenth of its weight of soluble matter (Bishop Watson), so that 
the following quantity of such a mixture would be nearly equal in effi- 
cacy to the saline matter of one ton of wood ash. 

Crude Potash 60 lbs. at a cost of 15s. 

Crystallized Carbonate of Soda . 60 " " " 7s. 

Sulphate of Soda 20 '♦ ? .^ ,, 

Common Salt 20 " ^ 

160 243. 

"Where the wood ash costs only a shilling a bushel (or c£2 a ton), it 
would obviously be more economical to employ this mixture, were the 
efficacy of wood ashes dependent solely upon the soluble saline matter 
they are capable of yielding on the first washing with water. But they 
contain also a greater or less quantity of imperfectly burned carbon- 
aceous matter, the effect of which upon vegetation cannot be precisely 
estimated, and a large proportion — nine-tenths, perhaps, of their whole 
weight — of insoluble carbonates, silicates, and phosphates of potash, 
lime, and magnesia, which are known more permanently to influence 
the fertility of the land to which they are applied.* 

c. Washed or lixiviated wood-ashes. — In countries where wood ashes 
are washed for the manufacture of the pot and pearl ash of commerce 
(Lee. IX., § 4), this insoluble portion collects in large quantities. It is 
also present in the refuse of the soap makers, where wood ash is em- 
ployed for the manufacture of soft soap. The composition of this inso- 
luble matter varies very much, not only with the kind of wood from 

* Some discussion has lately arisen in America (Silliman^s Journal, xlii. p. 165, and xliii. 
p. 80), in regard to the fact, in itself sufficiently interesting, that wood ashes, when thrown 
together in heaps, not unfrequently take fire, becoming red hot throughout their whole mass, 
and sometimes occasioning serious accidents. Such ashes always contain a quantity of 
minutely divided carbonaceous matter, which, like the impalpable charcoal powder of the 
gunpowder manufactories, may have the property of absorbing much air into its pores, and 
of thus undergoing a spontaneous elevation of temperature. I throw it out, however, as a 
more probable conjecture, that during the combustion of the wood a portion of the potash 
has been decomposed by the charcoal, and converted into potassium (potash consisting of 
potassium and oxygen, Lee. IX., § 4). When exposed to the air and to moisture this potas- 
sium gradually absorbs oxygen and spontaneously burns, again forming potash. That* such 
a decomposition may lake place where wood or other vegetable matter is burned with little 
access of air will readily be granted, but it is not so obvious that it can take place in an open 
fire. But even in an open fire, or in an open capsule, particles of potassium may remain in 
the pores of the unburned charcoal, or more frequently may be covered over with a glaze of 
melted potash, by which further combustion will be prevented. That this really does hap- 
pen any one must have satisfied himself who has been in the habit of burning vegetable 
substances for the purpose of determining the propoi-fion of ash they leave. The glaze of 
melted alkaline matter often renders the complete combustion a very difficult and tedious 
matter. That potassium is formed during this process is rendered further probable by the 
observation that the quantity of potash obtained from wood or other vegetable ash is less 
when the wood has been burned at a high than at a low temperature. The potassium, which 
is volatile, may have been dissipated in vapour. 

It is probable that a spontaneous combustion similar to that observed in America may oc- 
casionally take place in the heaps of ashes left to stand upon our fields after paring and 
burning — and hence probably has arisen the practical rule, to spread the ashes as soon as 
possible after the burning is finished. If allowed to remain, they are said '■'•to take hold of the 
land," and when it is of clay, to burn it into brick. An instance of such combustion is mrn- 
tloned as having occurred at Chatteris, in the Isle of Ely, where an entire common was 
burned 16 or 18 inches deep, down to the very gravel.— See British Husbandrr/, II., p. 350. 



COMPOSITIOX OF LIXIVIATED WOOD ASHES. 353 

whicli the ash is made, but also with the temperature it is allowed to at- 
tain in burnina;. The former fact is illustrated by the following analysis 
made by Berthier, of the insoluble matter left by the ash of five differ- 
ent species of wood carefully burned by himself: — 





Oak. 


Lime. 


Birch. 


Pitch Pine. 


Scotch Fir. 


Beech, 


Silica 


3-8 


20 


55 


130 


4-6 


5-8 


Lime 


54-8 


51-8 


52-2 


27-2 


423 


42-6 


Magnesia . 


0-6 


2-2 


30 


8-7 


10-5 


70 


Oxide of Iron . 


— 


01 


05 


22-3 


01 


1-5 


Oxide of Mano:anese — 


06 


3-5 


55 


0-4 


4-5 


Phosphoric Acid 


0-8 


2-8 


43 


1-8 


10 


5-7 


Carbonic Acid . 


39G 


39-8 


310 


21-5 


360 


32-9 


Carbon. . 


— 


— 


— 


— 


4-8 


— 



99-6 100 100 100 997 100 

The numbers in these several columns differ very much from each 
other, but the constitution of the insoluble part of the ash he obtained 
probably differed in every case from that which would have been left 
by the ash of the same wood burned on the large scale, and in the open 
air. This is to be inferred from the total absence of potash and soda in 
the lixiviated ash — while it is well known that common lixiviated wood 
ash contains a notable quantity of both. This arises from the high tem- 
perature at which wood is commonly burned, causing a greater or less 
portion of the potash and soda to combine with the silica, and to form 
insoluble silicates, which remain behind along with the lime and other 
earthy matter, when the ash is washed with water. It is to these sili- 
cates as well as to the large quantity of lime, magnesia, and phosphoric 
acid it contains, that common wood ash owes the more permarient effects 
upon the land, which it is known to have produced. When the rains 
have washed out or the crops carried off the more soluble part from the 
soil, these insoluble compounds still remain to exercise a more slow and 
enduring influence upon the after-produce. 

Still from the absence of this soluble portion, the action of lixiviated 
wood ash is not .so apparent and energetic, and it may therefore be safely 
added to the land in much larger quantity. Applied at the rate of two 
tons an acre, its effects have been observed to continue for 15 or 20 years. 
It is most beneficial upon clay soils, and is said especially to promote 
the growth of oats. 

I am not aware that in any part of the British Islands this refuse ash 
is to be obtained in large quantity, but in North America much of it is 
thrown away as waste, which might be advantageously restored to the 
land on which the wood had grown. 

d. Kelp is the name given in this country* to the ash left by marine 
plants when burned. It used to be extensively prepared in the Western 
Islands, but the low price at which carbonate of soda can now be manu- 
factured has so reduced the price and the demand for kelp as almost to 
drive it from the market. As a natural mixture, however, which can 
now be obtained at a cheap rate (about <£3. a ton), and which has been 
proved to be useful to vegetation in a high degree,f it is very desirable 

• In Brittany and Normandy it is called varec, while that of Spain -is known by the name 
of barilla. 

t Prize Essays of the IL'gh'.and Society, vol.". 1 and 4. 

30* 



356 



COMPOSITION AND USE OF KELP. 



that accurate experiments should be instituted with the view of deter- 
mining the precise extent of its action, as well as the crops and soils to 
which it can be most advantageously and most economically applied. 

Like wood ashes, kelp varies in composition with the species and age 
of the marine plants (sea weeds) from which it is prepared, and like 
them also it consists of a soluble and insoluble portion. Two samples 
from different localities in the Isle of Sky, analyzed by Dr. Ure,* con- 
sisted of — 



Soluble Portion. 
Carbonate of Soda with Sulphuret of Sodium 

Sulphate of Soda 

Common Salt 

Chloride of Potassium .... 



Insoluble Portion 
Carbonate of Lime . 
Silica .... 
Alumina and Oxide of Iron 
Gypsum .... 
Sulphur and loss 







Normandy, 


Heisker. 


Ron a. 


Gay-Lussac. 


8-5 


55 


— 


80 


190 


— 


: 36 5 


375 


(56.0 
)25.0 


530 


620 




240 


100 


__ 


8-0 


— 


— 


90 


100 


— 


— 


9-5 


— 


60 


8-5 


— 



100 



100 



Besides these constituents, however, the soluble portion contains iodide 
of potassium or sodium in variable quantity, and the insoluble more or 
less of potash and soda in the state of silicates. 

Kelp may be applied to the land in nearly the same circumstances as 
wood-ash — but for this purpose it would probably be better to burn the 
sea weed at a lower temperature than is usually employed. By this 
means, being prevented from melting, it would be obtained at once in the 
state of a fine powder, and would be richer in potash and soda. 

It might lead to important results of a practical nature, were a series 
of precise experiments made with this finely divided kelp as a manuref 
— especially in inland situations — for though the variable proportion of 
its constituents will always cause a degree of uncertainty in regard to 
the action of the ash of marine plants — yet if the quantity of chloride 
of potassium it contains be on an average nearly as great as is stated 
above in the analysis of Gay-Lussac — kelp will really be the cheapest 
form in which we can at present apply potash to the land. 

e. Straw ashes. — The ashes obtained by burning the straw of oats, 
barley, wheat, and rye, contain a natural mixture of saline substances, 
which is exceedingly valuable as a manure to almost every crop. The 
proportion of the several constituents of this mixture, however, is diffe- 
rent, according as the one or the other kind of straw is burned. Thus, 100 
parts of each variety of ash — in the samples analyzed by SprengelJ 
—consisted of— 



• Dictionary of Arts and Manufactures, p. 726. 

t For some other suggestions on thi.^ subject. I beg to refer the reader to the Prize Essays 
arul Transaclions of the Highland arid Agricultural Society, xiv., p. 508. 

t sprengel, Chemie II. t 



SOILS ON WHICH STRAW ASH MAY BE USED. 



357 





Oats. 


Barley. 


Wheat. 


Rye. 


Rape. 


Potash . 


15'2 


34 


0-6 


1-2 


18-8 


Soda . . . . 


trace. 


0-9 


0-8 


04 


11-2 


Lime 


2-6 


10-5 


6-8 


6-4 


169 


Magnesia 


0-4 


1-4 


09 


0-4 


31 


Silica 


800 


735 


81-6 


82-2 


21 


Alumina 


01 


2-8 > 








Oxide of Iron . 


trace. 


0-2 > 


2G 


0-9 


23 


Oxide of Manganese 


trace. 


0-3) 








Phosphoric Acid . 


02 


^5 


4-8 


1-8 


9-9 


Sulphuric Acid 


1-4 


2-2 


10 


61 


13-3 


Chlorine 


01 


1-3 


09 


0-6 


11-4 


Carbonic Acid 


— 


— 


— 


— 


110 



100 



100 



100 



100 



100 



The most striking differences in the above table are the comparatively 
large quantity of potash in the oat straw — of lime in that of barley— 
of phosporic acid in that of wheal — of sulphuric acid in that of rye — 
and of all the saline substances in rape straw. These differences are not 
to be considered as constant, nor will the numbers in any of the above 
columns represent correctly the composition of the ash of any variety 
of straw we may happen to burn (Lee. X., § 4), but they may be safely 
depended upon as showing the general composition of such ashes as well 
as the general differences which may be expected to prevail among them. 

That such ashes should prove useful to vegetation might be inferred 
not only from their containing many saline substances which are known 
to act beneficially when applied to the land, but from the fact that they 
have actually been obtained from vegetable substances. If inorganic 
matter be necessary to the growth of wheat, then surely the mixture of 
such matters contained in the ash of wheat straw is more like!)' than any 
other we can apply to promote the growth of the young wheat plant. A 
question might even be raised whether or not in some soils, rich in vege- 
table matter, the ash alone would not produce as visible an effect upon the 
coming crop, as the direct application of the straw, either in the dry 
state, or in the form of rotted farm-yard manure. And this question 
would seem to be answered in the affirmative, by the result of many 
trials of straw ashes which have been made in Lincolnshire. In this 
county the ash of five tons of straw has been found superior in efficacy 
to ten tons of farm-yard manure.* This is perfectly consistent with the- 
ory, yet as vegetable matter appears really essential to a fertile soil, and 
as the quantity of this vegetable matter is lessened in some degree by 
every corn crop we raise, it cannot be good husbandry to manure for a 
succession of rotations with saline substances only. The richest soil by 
this procedure must ultimately be exhausted. On the other hand, where 
much vegetable matter exists, and especially what is usually called 
inert vegetable matter, it may be an evidence of great skill in the prac- 
tical farmer to apply for a titne the ashes only of his straw — or some 
other saline mixture to his land. 

The practice of burning the stubble on a windy day has been found 
in the East Riding of Yorkshire to produce better clover, and to cause 

• Survey of Lincolnshire, p. 304, quoted in British Husbandry, II,, p. 334. 



358 COMPARATIVE EFFECTS OF STRAW AND STRAW ASH. 

a larger return of wheat* — for this purpose, however, the stubble must 
be left of considerable length. In Germany, rape straw — which the 
above table shows to be rich in saline and earthy matter, and, therefore, 
exhausting to the land — is spread over the field and burned in a similar 
manner. The destruction of weeds and insects which attends this prac- 
tice, is mentioned as one of its collateral ad vantages. f 

In the United States, where, according to Capt. Barclay, the straw is 
burned merely in order that it may be got rid of,t it would cost little la- 
bour to apply the ash to the soil from which the straw was reaped, while 
it would certainly enlarge the future produce — and in Little Russia, 
where from the absence of wood the straw is universally burned for fuel, 
and the ashes afterwards consigned to the nearest river, the same prac- 
tice might be beneficially adopted. However fertile, and apparently 
inexhaustible, the soils in these countries may appear, the time must 
come when the present mode of treatment will have more or less ex- 
hausted their productive powers. 

It is not advisable, as I have already said, wholly to snbstiinte the a.'h 
for the straw in ordinary soils, or in any soils for a length of time, ^et 
that it may be partially so substituted with good effect — or that strav/ 
ashes will alone give a large increase of the corn crop, and therefi.re 
should never be wasted — is shewn by the following comparative expeii- 
ments, conducted as such experiments should be, during an entire rota- 
lion of four years. The quantity of manure applied, and the produce 
per imperial acre, were as follows : — 

15 cwt. barley 3 tons stable dung 2 tons of rotten 

No manure. straw burnecl in the straw dung, eight 

on the ground. state. months old. 

1°. Turnips, 22 lbs. 8* cwt. I8f cwt. 16 'A cwt. 

2°. Barley. 14^ bush. 301 bush. 30* bush. 36f bush. 

3°. Clover,' 8 cwt. 18 cwt. 20 cwt. 21 cwt. 

4°. Oats, 32 bush. 18 bush. 38 bush. 40 bush. 

The kind of soil on which this experiment was made is not staled, j| 
but it appears to show, as we should expect, that the effects of straw ash 
are particullarly exerted in promoting the growth of the corn plants and 
grasses which contain much silicious matter in their stems — in short, of 
plants similar to those froin which the ash has been derived. 

Theory of lite action of straw ash. — That it should especially pro- 
mote the growth of such plants appears most natural, if we consider 
only the source from which it has been obtained, but it is fully explained 
by a further chemical examination of the ash itself. The soluble mat- 
ter of wood ash in general contains but a small quantity of silica — 
while that part of the straw ash which is taken up by water contains 
very much. Thus a wheat ash analyzed b}'' Berthier contained of 

PER CENT. 

Soluble salts 19 

Insoluble matter 81 



100 



* British Husbandry, 11 , p. 333. 

t Sprengel, Lehre vom Dvvger^ p. 355- 

I Agricultural Tour in the United States, pp. 42 and 54. 

§ British Husbandry, II., p. 243. 



COMPOSITION AND USE OF DUTCH ASHES. 



'359 



and that which was dissolved by water consisted of 

PBR CENT. 

Silica 35 

Chlorine 13 

Potash and soda 50 

Sulphuric acid . - 2 

100 
so that it was a mixture of soluble silicates and chlorides with a little 
sulphate of potash and soda. These soluble silicates will find an easy 
admission into the roots of plants, and will readily supply to the young 
stems of the corn plants and grasses the silica which is indispensable to 
their healthy growth. 

/. Turf or peat ashes, obtained by the burning of peat of various 
qualities, are also applied with advantage to the land in many districts. 
They consist of a mixture in which gypsum is usually the predomi- 
nating useful ingredient — the alkaline salts being present in very small 
proportion. Of ashes of this kind those made in Holland, and generally 
distinguished by the name of Dutch ashes, are best known, and have 
been most frequently analyzed. The following table exhibits the com- 
position of some varieties of ashes from the peat of Holland and from the 
heath of Luneburg, examined by Sprengel : — 

Luneburg Ashes (reddish). 



Best 

quality 

Silica .... ... 47-1 

Alumina 4'5 

Oxide of Iron 66 

Do. of Manganese ... 10 

Lime 136 

Magnesia 4*9 



Dutch Ashes (grey). 

Worst 
quality. 



Potash 
Soda 



Sulphuric Acid 
Phosphoric Acid 



0-2 
10 

7-2 



Inferior 
quality. 
55-9 
35 
5-4 
4-3 
8-6 
1-6 
0-2 
3-9 

6-4 



20 0-8 



1-2 



Chlorine 

Carbonic Acid 4'1 

Charred Turf 66 



30 
6-4 



70.4 
41 
41 
02 
61 
3-9 
01 
0-4 

3-4 

1-3 

.0-5 
5-5 



Good 
quality. 

31-7 
51 

17-7 
0-5 

31-9 
10 
01 
01 

6-2 



Producing 

little effect. 

43-3 

9-7 

19-3 

35 

71 

46 



1-2 

01 
4-4 



Gypsum 

0-2 

Phosph.ofLime 

0-2 

Common Salt 

01 

120 



1000 1000 1000 1 1000 1000* 

In the most useful varieties of these ashes it appears, from the above 
analyses, that lime abounds — partly in combination with sulphuric and 
phosphoric acids, forming gypsum and phosphate of lime — and partly 
with carbonic acid, forming carbonate. These compounds of lime, 
therefore, may be regarded as the active ingredients of peat ashes. 

Yet the small quantity of saline matter they contain is not to be con- 
sidered as wholly without effect. For the Dutch ashes are often ap- 
plied to the land to the extent of two tons an acre — a quantity which, 



* Sprengel Lehre vom Dunger, p. 363 e< seq. 



360 COMPOSITION AND USE OF COAL ASHES. 



^ 



even when the proportion of alkali does not exceed one per cent., will 
contain 45 lbs. of potash or soda, equal to twice that weight of sulphates 
or of common salt. To the minute quantity of saline matters present 
in them, therefore, peat ashes may owe a portion of their beneficial 
influence, and to the almost total absence of such compounds from the 
less valuable sorts, their inferior estimation may have in part arisen. 

In Holland, when applied to the corn crops, they are either ploughed 
in, drilled in with the seed, or applied as a top dressing to the young 
shoots in autumn or spring. Lucerne, clover, and meadow grass are 
dressed with it in spring at the rate of 15 to 18 cwt. per acre, and the 
latter a second time with an equal quantity after the first cutting. In 
Belgium the Dutch ashes are applied to clover, rape, potatoes, flax, and 
peas — but never to barley. In Luneburg the turf ash which abounds 
in oxide of iron is applied at the rate of 3 or 4 tons per acre, and by this 
means the physical character of the clay soils, as Avell as their chemical 
constitution, is altered and improved. 

In England peat is in many places burned for the sake of the ashes 
it yields. Among the most celebrated for their fertilizing ([ualities are 
the reddish turf ashes of Newbury, in Berkshire. The soil from beneath 
which the turf is taken abounds in lime, and the ashes are said to con- 
tain from one-fourth to one-third of their weight of gypsum.* They 
are used largely both in Berkshire and Hampshire, and are chiefly 
applied to green crops, and especially to clover.f 

g. Coal ashes are a mixture of which the composition is very variable. 
They consist, however, in general, of lime often in the state of gypsum, 
of silica, and of alumina mixed with a quantity of bulky and porous 
cinders or half-burned coal. The ash of a coal from St. Etienne, in 
France, after all the carbonaceous matter had been burned away, was 
found by Berthier to consist of 

PER CENT. 

Alumina, insoluble in acids 62 

Alumina, soluble 5 

Lime 6 

Magnesia 8 

Oxide of Manganese 3 

Oxide and Sulphuret of Iron 16 

• 100 

Such a mixture as this would no doubt benefit many soils by the 
alumina as well as by the lime and raaenesia it contains ; but in the 
English and Scotch coal ashes a small quantity of alkaline matter, 
chiefly soda,t is generally present. The constitution of the ash of our 
best coals, therefore, may be considered as very nearly resembling that 
of peat ash, and as susceptible of similar applications. When well 
burned, it can in many cases be applied with good effects as a top- 
dressing to grass lands which are overgrown with moss ; while the 



British Husbandry^ II., p. 334. 

50 bushels per acre (at 3it. a bu 
h.— Morton " On Soils," p. 170. 

I From the common salt with which our coal is so often impregnated. 



t 50 bushels per acre (at 3il. a bushel, or 12s. 6d. an acre) increase the clover crop fuilv one 
fifth.— Morton " On Soils," p. 170. 



CANE ASHES. — CRUSHED AND DECAYED TRAl'S AND LAVAS. 361 

admixttire of cinders in the ash of the less perfectly burned coal pro- 
duces a favourable pliysical change u]:)on strong clay soils. 

h. Cane Ashes. — I may allude here to the advantage which in sugar- 
growing countries may be obtained from the restoration of the cane ash 
to the fields in which the canes have grown. After the canes have been 
crushed in the mill they are usually employed as fuel in boiling down 
the syrup, and the ash, which is not unfrequently more or less melted, 
is, 1 believe, almost uniformly neglected — at all events is seldom ap- 
plied again to the land. According to the principles I have so often 
illustrated in the present Lectures, such procedure must sooner or later 
exhaust the soil of those saline substances which are most essential to 
the growth of the cane plant. If the ash were applied as a top-dressing 
to the young canes, or put into the cane holes near the roots — having 
been previously mixed with a quantity of wood-ash, and crushed if it 
happen to have been melted — this exhaustion would necessarily take 
place much more slowly. 

i. Crushed Granite. — We have already seen that the felspar existing 
in granite contains much silicate of potash and alumina. It is, in fact, 
a natural mixture, which in many instances may be beneficially ap- 
plied, especially to soils which abound in lime. It is many years since 
Fuchs proposed to manufacture potash from felspar and mica by 
mixing them with quicklime, calcining in a furnace, and then washing 
with water. By this means he said felspar might be made to yield 
one-fifth of its weight of potash.* Mr. Prideaux has lately proposed to 
mix up crushed granite aud quicklime, to slake them together, and to 
allow the mixture to stand in covered heaps for some months, when it 
may be applied as a top-dressing, and will readily give out potash to 
the soil. Fragments of granite are easily crushed when they have been 
previously heated to redness, and there can be little doubt, I think, that 
such a mixture as that recommended by Mr. Prideaux would unite 
many of the good effects of wood ashes and of lime. 

k. Crushed Trap. — I need not again remind you of the natural fer- 
tility of decayed trap soils (Lee. XII., §4) and of the injprovement which 
in many districts may be effected by applying them to the land. When 
granite decays, the potash of the felspar is washed out by the rains, and 
an unproductive soil remains — when trap decays, on the other hand, the 
lime by which it is characterised is not soon dissolved out, so that the 
soil which is produced is not only fertile in itself, but is capable of being 
employed as a fertilizing mixture for other soils. Thus when itismuch 
decayed it is dug out from pits both in Cornwall and in Scotland, and 
is applied like marl to the land. 

I. Crushed Lavas. — Of the fertile and fertilizing nature of the crushed 
or decayed lavas I have also already spoken to you (Lee. XII., § 4). 
In St. Michael's, one of the Azores, the natives pound the volcanic mat- 
ter and spread it on the ground, where it speedily becomes a rich mould 
capable of bearing luxuriant crops. At the foot of Mount Etna, when- 
ever a crevice appears in the old lavas, a branch or joint of an Opuntia 
{Cactus Opuntia — European Indian-Fig) is stuck in, when the roots in- 

* Journal of the Royal Institution^ I., p. 184. 

t DecandoUe quoted in the Quart. Journ. of Agr., IV. p. 737. 



362 EXPERIMENTS WITH MIXED MANURES. 

sinuate themselves into every fissure, expand, and finally break up the 
lava into fragments. These plants are thus not only the means of pro- 
ducing a soil, but they yield also much fruit, which is sold as a refresh- 
ing food throughout ail the towns of Sicily. f 

These are all so many natural mineral mixtures of which we may 
either directly avail ourselves, or which we may imitate by art. 



Experiments with mixed manures. 

Note. — As a valuable appendix to the preceding observations on 
mixed manures, I am permitted to insert the following very interesting 
resuhs obtained during the present season, 1842, from experiments made 
on the estate of Mr. Burnet, of Gadgirth, near Ayr. The crop to which 
the several manures were applied was wheat of the eclipse \aviety, sown 
on the 29th of October, 1841, and reaped on the 15th of August last. 
The soil is a loam with subsoil of clay, tile drained and trenched plough- 
ed. It had been in beans the previous year, and gave six quarters per 
acre, which were sold at 46s. a quarter. No manure had been applied 
with the bean crop, and except a good dose of lime before sowing the 
wheat, nothing but the saline mixtures mentioned below was applied 
with this latter crop. 

PRODUCE. 100 lbs. of grain 

Application per imperial acre. , ' ^ Weight per produced of 

Straw. Grain. bushel. fine flour. 

cwt. bush. lbs. lbs. lbs. 

Sulphate Of Ammonia, 2 cwt.*) 35 3^ ^^ g^ gg 

Wood-ashes, 4 cwt. ... J * * 

Sulphate of Ammonia, 2 cwt. 
Sulphate of Soda, 2 cwt. . 
Wood-ashes, 4 cwt. . . . 
Sulpnate of Ammonia, 2 cwt. 
Common Salt, 2 cwt. . . 
Wood-ashes, 4 cwt. . . . 
Sulphate of Ammonia, 2 cwt. 
Nitrate of Soda, 1 cwt. . . 
AVood-ashes, 4 cwt. . . . 
No Application ' . 29| 31 38 61 1 ^6l 

The reader will observe here that though the first mixture produced 
a large increase both of straw and grain, a still larger additional increase 
was caused by mixing with the substances of which it consisted either com- 
mon salt or sulphate of soda or nitrate of soda. Each of these three substan- 
ces produced nearly the same effect. The soda, therefore, more than the 
acid with which it was combined, must in these cases have acted bene- 
ficially. The comparatively small proportion of fine flour yielded by 
the nitrated wheat, and the comparatively large proportion obtained 
from that to which no application was made, are also highly deserving 
of notice. 

Mr. Burnet has transmitted to me samples of the flour from these 
several growths of wheat, with the view of determining the relative 

* The sulphate of ammonia was prepared from urine, and, therefore, contained other ad- 
mi.xtures (page 349). Tlie straw was strongest, coarsest, and longest in ripening, where 
this sulphate was applied. The two guanos produced little luxuriance, but the lots to which 
they were applied were soonest ripe. 



44| 49 6 60 63J 

45 49 60 65| 
> 

44i 48 20 59 54| 



IMPORTANCE OF SUCH EXPERIMENTS. 363 

proportions of gluten they contain. The result of this examination, 
which cannot fail to be interesting, will be given in a succeeding Lec- 
ture—before which, however, I hope the whole of Mr. Burnet's experi- 
ments will be laid before the public. 

It will be observed that Mr. Burnet has exercised a sound discretion 
in making and trying mixtures not hitherto specifically recommended. 
It is by the result of such varied experimental trials, made by intelli- 
gent practical men, on different soils and crops, and with mixtures of 
which the constitution is exactly known, that we shall be able hereafter to 
correct our theoretical principles— as well as to simphfy and render 
more sure our general practice.* 

• While this sheet is going through the press, I am informed that the silicate of potash. 
referred to at page 349, is now manufactured by the Messrs. Dymond, of London, and 
may be obtained from the London dealers at 56s. a cwt. I expect also, that asilicate of soda 
will soon be brought into the market by the Messrs. Cookson's, of the Jarrow Alkali Works, 
at a much lower price. The probable efficacy of these substances, as manures, has, no 
doubt, been extolled too highly by some-their real efficacy, however, is well deservmg of 
inves(\-ation. I shall insert in the Appendix No. VII, therefore, some suggestions for experi- 
ments with these substances, in the hope that during the ensuing spring, 1843, some experi- 
ments oa the subject may be made. 



31 



LECTURE XVII. 

Use of lime as a manure. Value of lime in improving the soil. Of the composition of com- 
mon and magnesian lime-stones. Burning and slaking of lime. Changes which slaked 
lime untiergoes by exposure to the air. y-dUoMS natural states in which carbonate of lime 
is applied to the land. Marl — shell and coral sand, — lime stone sand and gravel.— crushed 
lime stone. Chemical composition of various marls, and shell and limestone sands. 
Their effects on the soil. Use of chalk. Is lime necessary to the soil? Exhausting ef- 
fect of lime. Analogy between this action of lime and that of wood-ashes. Quantity of 
lime to be applied. Effects of an overdose. Form in which it may be most prudently 
used. When it ought to be applied in reference to the season — to the rotation — and to the 
application of manure. Its general and special effects on different soils and crops. Cir- 
cumstances which influence its action. Length of time during which its effects are per- 
ceptible. Theory of the action of lime. Necessity and nature of the exhaustion which 
it sometimes produces. Sinking of lime into the soil. Wliy the application of lime must 
be repeated. Action of lime on living animals and vegetables. Suggestions of theory. 
Use of silicate of lime. 

Having explained to you the action of the most important saline and 
mixed mineral substances which are or may be beneficially applied to 
the soil, I have now to draw your attention to the use of lime — the most 
valuable and the most extensively used of all the mineral substances 
that have ever been made available in practical agriculture. It has, and 
with much reason, been called " the basis of all good husbandry" — it well 
deserves, therefore, your most serious attention as practical men, and on 
my part the application of every chemical light by which its usefulness 
may be explained and your practice guided. This consideration also 
will justify me in dwelling upon it with some detail, and in illustrating 
separately the various points, both of theory and practice, which present 
themselves to us, when we study the history of its almost universal ap- 
plication to the soil. 

§ 1. Of the composition of common and magnesian lime-stones. 

1°. Common lime-stones. — Lime is never met with in nature except 
in a state of chemical combination (Lee. I., § 5,) with some other 
substance. That which is usually employed in agriculture is met with 
in the state of carbonate. 

Carbonate of lime, or common lime-stone, consists of lime and car- 
bonic acid, and when perfectly pure and dry, in the following propor- 
tions : — 

"^5?^;} per cent. 

Carbonic acid, 43-7 ^ 

or one ton of pure dry carbonate of 
lime contains \\\ cwts. of lime. 
100 J 
Limestones, however, are seldom pure. They always contain a sensi- 
ble quantity of other earthy matter, chiefly silica, alumina, and oxide 
of iron, with a trace of phosphate of litTie, sometimes of potash and soda, 
and often of animal and other organic matter. In lime-stones of the 
best ([uality tlie foreign earthy matter or impurity does not exceed 5 per 
cent, of the whole — while it is often very much less. The chalks and 



Lime, . . . 56*3 



COMMON AND MAGNESIAN LIME-STONES. 



365 



mountain lime-stones are generally of tliis kind. In those of inferior 
quality it may amount to ] 2 or 20 per cent., while many calcareous beds 
are met with in which the proportion of lime is so small that they will 
not burn into agricultural or ordinary building lime — refusing to slake or to 
fall to powder when moistened with water. Of this kind is the Irish caljy 
and the lime-stone nodules which are burned for the manufacture of 
hydraulic limes or cements.* It is easy to ascertain the quantity of 
earthy matter contained in lime-stone, by simply introducing a known 
weight of it into cold diluted muriatic acid and observing or weigh- 
ing the part which, after 12 hours, refuses to dissolve or to exhibit any 
effervescence. It is to the presence of these insoluble impurities that 
lime-stones in general owe their colour, pure carbonate of lime being 
perfectly white. 

2°. Magnesian lime-stove. — Though often nearly white, the mag- 
nesian lime-stones of our island are generally of a yellow colour. They 
cannot by the eye be distinguished from common lime-stones of a similar 
colour, but they are chai'acterised by containing a greater or less pro- 
portion of carbonate of magnesia, which is more or less easily detected 

by analysis. Pure carbonate of magnesia consists of 
per cent. 
Carbonic acid, 51*7 "j 
Magnesia . 48-3 I or one ton of pure dry carbonate of mag- 

j nesia contains 9| cwts. of magnesia. 

100 J 
It contains, therefore, a considerably larger proportion of carbonic 
acid than is present in carbonate of lime. 

Magnesian lime-stone is very abundant, is indeed the prevailing rock 
in many parts of England (Lee. XL, sec. 4), but the proportion of car- 
bonate of magnesia it contains is very various in different localities. 
Even in the same quarry difTerent beds contain very unlike proportions 
of magnesia, and are therefore more or less fitted for agricultural pur- 
poses. Thus several varieties of this lime-stone, examined by myself, 
from different parts of the county of Durham, contained the two car- 
bonates in the following proportions : — 

Alumina, 
Carbonate Carb'ate Oxide of 

of of Iron,and Insoluble 

Lime. Magnesia. Phospho- matter, 
ric Acid. 
97-5 2-5 trace 
980 1-61 27 



Garmondsway 
Stony-gate . 

Fulwell . . 

Seaham (A) . 

" (B) . 
Hartlepool 



950 21 



Humbledon'Hill(A)57-9 



Ferry hill 



23 

13 

44-93 

41-8 
(B560-41 38-78 
541 44-72 



965 
950 
54-5 



03 

0-2 
0-2 
0-33 

1 

1-58 



trace Hard compact grey. 
0-12 Crystalline fine grained yellow 
n.f S Honey-combed crystalline 

) yellow, 
1 Hard fine-grained compact. 
35 Hard porous brown. 
0-24 Oolitic yellow. 
028 Perfect encrinal columns. 
081 Consisting in part encrinal col. 
46 Yellowish compact. 



Some of these varieties, as we see, contain very little carbonate of 



* Thns that of Aberfhaw contains about 86 of carbonate of lime and 11 of clay, &c. ; that 
of Yorksliire 62 of carbonate of lime and 34 of clay ; of Slieppy 66 of carbonate of lime 
and 32 of clay. Tliese limestones are burned, and then crushed to an impalpable powder, 
which sets almost immediately when mixed up with water. 



366 OF THE BURNING AND SLAKING OF LIME- 

magnesia, and, therefore, are found to produce excellent lime for agri- 
cultural purposes — while in others this substance forms nearly one-half 
of the whole weight of the rock. Similar differences are found to pre- 
vail in almost every locality. 

This admixture of magnesia in greater or less quantity is not confined 
to the lime-stones of the magnesian lime-stone formation properly so |j 
called. It is found in sensible quantity in certain beds of lime-stone in • 
nearly every geological formation, and there are few natural lime-stones 
of any kind in which traces of it may not be discovered by a carefully 
conducted chemical examination. 

The simplest method of detecting magnesia in a limestone is to dis- 
solve it in diluted muriatic acid, and then to pour clear lime water into 
the filtered solution. If a light white powder fall, it is magnesia. The 
relative proportions in two lime-stones may be estimated pretty nearly 
by dissolving an equal weight of each, pouring the filtered solutions into 
bottles which can be corked, and then filling up both with lime water. 
On subsiding, the relative bulks of the precipitates will indicate the 
respective richness of the two varieties in magnesia. 

§ 2. Of the burning and slaking of lime. 

Burning. — When carbonate of lime or carbonate of magnesia is 
heated to a high temperature in the open air the carbonic acid they 
severally contain is driven off, and the lime or magnesia remains in the 
caustic state. When thus heated the carbonate of magnesia parts with 
its carbonic acid more S2)eedily and at a lower temperature than car- 
bonate of lime. 

On the large scale this burning is conducted in lime kilns, one ton good 
lime-stone yielding about 11 cwts. of burned, shell, quick, or causticlime. 

Slaking. — When this shell or quick-lime, as it is taken from the 
kiln, is plunged into water for a short time and then withdrawn, or when 
a quantity of water is poured upon it, heat is developed, the lime swells, 
cracks, gives off much watery vapour, and finally falls to a fine, bulky, 
more or less white powder. These appearances are more or less rapid 
and striking according to the quality of the lime, and the time that has 
been allowed to elapse after the burning, before the water was applied. 
All lime becomes difficult to slake when it has been for some time 
exposed to the air. When the slaking is rapid as in the rich limes, the 
heat produced is sufficient to kindle gunpowder strewed upon it, and the 
increase of bulk is from 2 to 3i times that of the original lime shells. If 
the water be thrown on so rapidly or in such quantity as to chill the 
lime or any part of it, the powder will be gritty, will contain many little 
lumps which refuse to slake, Avill also be less bulky and less minutely 
divided, and therefore will be less fitted either for agricultural or for 
building purposes. 

When quick-lime is left in the open air, or is covered over with sods 
in a shallow pit, it gradually absorbs water from the air and from tlie 
soil, and falls, though much more slowly, and with little sensible deve- 
lopment of heat, into a similar fine powder. In the rich limes the 
increase of bulk may be 3 or 3i times, in the poorer, or such as contain 
much earthy matter, it may be less than twice. 

Hydrate of Lime. — When quick-lime is thus slaked it combines with 



FURTHER CHANGES UNDERGONE BY SLAKED LIME. 367 

the water which is added to it, and becomes converted into a milder or 
less caustic compound, which among chemists is known by the name of 
hydrate of lime. This hydrate consists of 
per cent. 
Lime . . . 76 ? or one ton of pure burned lime becomes 
Water . . 24 ^ nearly 25 cwts. of slaked lime. 



100 
It is rare, however, that lime is so pure or so skilfully and perfectly 
slaked as to take up the whole of this proportion of water, or to increase 
quite so much as one-fourth part in weight. 

Hydrate of Magnesia. — When calcined or caustic magnesia is slaked, 
it also combines with water, but without becoming so sensibly hot as 
quick-lime does, and forms a hydrate, which consists of 
per cent. 
Magnesia 69-7 ? or one ton of pure burned magnesia be- 
Water . . 30-0 \ comes 28| cwts. of hydrate. 



100 

When magnesian lime is slaked, the fine powder which is obtained 
consists of a mixture of these two hydrates, in proportions which depend 
of course upon the composition of the original lime-stone. 

An important difference between these two hydrates is, that the hy- 
drate of magnesia will harden under water or in a wet soil in about 8 
days — forming a hydraulic cement. Hydrate of lime will not so 
harden, but a mixture of the two in the proportions in which they exist 
in the Hartlepool, Humbledon, and Ferryhill lime-stones (page 365), 
will harden under water, and form a solid mass. In the minute 
state of division in which lime is applied to the soil the particles, if it 
be a magnesian lime, will, in wet soils, or in the event of rainy weather 
ensuing immediately after its application, become granular and gritty, 
and cohere occasionally into lumps, on which the air will have little 
effect. This property is of considerable importance in connection with 
the further chemical changes which slaked limes undergo when exposed 
to the air or buried in the soil. 

§ 3. Changes which the hydrates of lime and magnesia undergo hy pro- 
longed exposure to the air. 

When the hydrates of lime or magnesia obtained by slaking are ex- 
posed to the open air, they gradually absorb carbonic acid from the at- 
mosphere, and tend to return to the state of carbonate in which they 
existed previous to burning. By mere exposure to the air, however, 
they do not attain to this state within any assignable time. In some 
walls 600 years old, the lime has been found to have absorbed only one- 
fourth of the carbonic acid necessar}'^ to convert the whole into carbon- 
ate; in others, built by the Romans 1800 years ago, the proportion ab- 
sorbed has not exceeded three-fourths of the quantity contained in natu- 
ral lime-stones. In damp situations the absorption of carbonic acid 
proceeds most slowly. 

1°. Change undergone hy pure lime during sjyontaneous slaking. — In 
consequence, however, of the strong tendency of caustic lime to absorb 
carbonic acid, a considerable quantity of the hydrate of lime first formed, 
31* 



368 OF CALCINED AND SLAKED MAGNESIA. 

during spontaneous slaking, becomes changed into carbonate during the 

slaking of the rest. But, when it has all completely fallen, the rapidity 

of the absorption ceases, and the fine slaked lime consists of 

Carbonate of lime 57*4 

Tj I . c ^' S lime . . 32*4 ) ' An a 

Hydrate of lime < ^ m r» ^ 42*6 

•^ I water, . 10-2 \ 



100 
or, a ton of lime, left in the open air till it has completely fallen to pow- 
der, contains about 8i cwt. in the state of hydrate. If left to slake in 
large heaps, the lime in the interior of those heaps will not absorb so 
much carbonic acid till after the lapse of a very considerable time. 
More caustic lime (hydrate) also will be present if it be left to slake, as 
is often done for agricultural purposes, in shallow pits covered with sods, 
to defend it from the air and the rains. 

After the lime has attained the state above described, and which is a 
chemical compound* of carbonate with hydrate of lime, the further ab- 
sorption of carbonic acid from the air proceeds very slowly, and is only 
completely effected after a very long period. 

2°. When slaked in the ordinary way lime falls to powder, without 
having absorbed any notable quantity of carbonic acid. Numerous 
small lumps also remain, which, though covered with a coating of hy- 
drate, have not themselves absorbed any water. The absorption of car- 
bonic acid by this slaked lime is at first very rapid, — so that where the 
full effect of caustic lime upon the soil is required, it ought to be 
ploughed in as early as possible, — but it gradually becomes more slow, 
a variable proportion of the compound of carbonate and hydrate above 
described is formed, and even when thinly scattered over a grass-field, 
an entire year may pass over without effecting the complete conversion 
of the whole into carbonate. 

3°. Calcined or burned magnesia^ whether in the pure state or'mixed 
with quick-lime, as in the magnesian limes, absorbs carbonic acid more 
slowly— 'and by mere exposure to the air will probably never return to 
its original condition of carbonate. 

When allowed to slake spontaneously, three-fourths of it become ul- 
timately changed into carbonate, and form a compound of hydrate and 
carbonate which is identical with the common uncalcined magnesia of 
the shops. This compoundf consists of — 

Carbonate of Magnesia 69*37 

Hydrate of Magnesia 16-03 

Water 14-60 



100 
and it undergoes no further change by continued exposure to the air. 

But if slaked by the direct application of water, magnesia, like lime, 
forms a hydrate only, without absorbing any sensible quantity of car- 

* This compound consists of one atom of carbonate of lime (CaO -J- COg) combined with 
one of hydrate (CaO + HO), and is represented shortly by Ca C -f CaH— in which Ca de- 
notes calcium (Lee. IX., §4), CaO or (Ja oxide of calcium or lime, COg or C carbonic acid 
(Lee. III., § I), and H O or H water (Lee. II., § 6). 

t It is represented by the formula 3 (Mg C -f H) -}- Mg K. 



STATES IN WHICH LKME IS APPLIED. 369 

bonic acid. The hydrate thus produced is met with in the form of 
mineral deposits on various parts of the earth's surface, and this mineral 
is not known to undergo any change or to absorb carbonic acid though 
exposed for a great length of time to the air. Wlien magnesian limes 
are slaked by water, therefore, the magnesia they contain may remain 
in whole or in part in the caustic state (of hydrate), which will change 
but slowly even when exposed to the air. When it is left to sponta- 
neous slaking, one-fourth of it at least will always remain in the caustic 
state, however long it may be exposed to the air. 

Should a lime be naturally of such a kind, or be so mixed with the 
ingredients of the soil as to form a hydraulic cement or an ordinary 
mortar, which will solidify when rains come upon it, or when the natu- 
ral moisture of the soil reaches it — the absorption of carbonic acid will 
in a great measure cease as it becomes solid, and a large proportion of 
tlie lime will remain caustic for an indefinite period. 

§ 4. States of chemical combination in which lime may he applied to 

the land. 

There are, therefore, four distinct states of chemical combination, in 
which pure lime may be artificially applied to the land. 

]°. Quick-lime or lime shells, in which the lime as it comes from the 
kiln is uncombined either with water or with carbonic acid. 

2°. Slaked lime or hydrate of lime, in which by the direct application 
of water it has been made to combine with about one-fourth of its weight 
of water. 

In both these states the lime is caustic, and may be properly spoken of 
as caustic lime. 

3°. Spontaneously slaked lime, in which one-half of the lime is com- 
bined with water and the other half with carbonic acid. In this state 
it is only half caustic. 

4°. Carbonate of lime — the state in which it occurs in nature, and to 
which burned lime, after long exposure to the air, more or less perfectly 
arrives. In this state lime possesses no caustic or alkaline (Lee. III., 
§ 5, note) properties, but is properly called mild lime. 

5°. ^i-carbonate of lime may be adverted to as a fifth stale of com- 
bination, in which, as I have previously explained to you (Lee. III., 
§ 1), nature usually applies lime to the land. In this state it is com- 
bined with a double proportion of carbonic acid, and is to a certain ex- 
tent readily soluble in water. Hence, springs are often impregnated 
with it, and the waters that gush from fissures in the lime-stone rocks 
spread it through the soil in their neighbourhood, and sweeten the land. 

I shall hereafter speak of these several states under the names of 
quick-lime, hydrate of lime, spontaneously slaked lime, carbonate of 
lime, and Bi-carbonate of lime. By adhering to these strictly correct 
names, we shall avoid some of that confusion into which those who have 
hitherto treated of the use of lime as a manure have unavoidably fallen. 
The term mild, you will understand, applies only to that which is en- 
tirely in the state of carbonate. 

Magnesia, in the magnesian limes, may in like manner be either in 
the state of calcined magnesia, of hydrate of magnesia, of spontaneously 
slaked — meaning by this the compound of hydrate with carbonate — of 



370 



VARIOUS NATURAL FORMS OF CARBONATE OF LIME. 



carbonate, or of Bi-carbonate of magnesia, the latter of which is soluble \ 
in water to a very considerable extent.* * 

§ 5. Of the various natural forms in which carbonate of lime is 
applied to the land. 

In the unburned or natural state, lime is met with on the earth's sur- 
face in numerous forms — in many of which it can be applied largely, 
easily, and with economy to the land. 

1°. Marl. — Of these forms that of marl occurs most abundantly, and 
is most extensively used in almost every country of Europe. By the 
term marl, is understood, as I explained to you when treating of soils 
(Lee. XL, § 3), an earthy mixture, which contains carbonate of lime, and 
effervesces more or less sensibly when an acid (vinegar or diluted mu- 
riatic acid — spirit of salt) is poured upon it. Generally, also, the tena- 
cious marls, when introduced into water, lose their coherence, and gra- 
dually fall to powder. This test is often employed to distinguish between 
marly and other clays, yet the falling asunder, though it afford a pre- 
sumption, is not an infallible proof that the substance tried is really a 
marl. 

Marls are of various colours, white, grey, yellow, blue, and of various 
degrees of coherence, some occurring in the form of a more or less fine, 
loose, sandy powder, others being tenacious and clayey, and others, 
again, hard and stony. These differences arise in part from the kind 
and proportion of the earthy matters they contain, and in part, also, from 
the nature of the locality, moist or dry, in which they are found. The 
hard and stony varieties are usually laid upon the land, and exposed to 
the pulverising influence of a winter's frost before they are either spread 
over the pasture or ploughed into the arable land. Some rich marls 
consist in part or in whole of broken and comminuted shells, which 
clearly indicate the source of the calcareous matter they contain. 



COMPOSITON OF MARLS FROM 

Weser- 
Luneburg. Osnabruck. Magdeburg. Brunswick, marsh. 



duaitz-Sand & Silica 

Alumina 

Oxides of Iron 
Do. of Magnesia . . 
Carbonate of Lime . 
Do" of Magnesia . . 
Sulphuretof Iron . 
Potash & Soda, com- > 
bined with Silica. ) 
Common Salt 
Gypsum .... 
Phosphate of Lime } 
(bone earth] ) 
Nitrate of Lime . . 

Organic Matter , . 



powdery. 

5-6 

0-4 

4-2 
trace 
85-5 

1-25 



stony. 

230 

100 

1-9 

trace 

350 

09 

— 73 

005 trace 



003 
OOG 

28 

001 

0-6 
100 



trace 
0-9 

05 



carbon 
20-5 



100 



clayey. 

58-4 

8-4 

6-7 

- 0-3 

18-2 
3-8 

1-6 

trace 
21 

05 



100 



loamy. 

734 
1-9 
3-2 
0-3 

181 
15 

0-8 

trace 
01 

0-7 



100 



powdery. 
78-9 
31 
3-8 
0-3 
8-2 
3-0 

0-9 

01 
05 

1-2 



Bruns- 
wick. 
stony. 

711 
40 
65 
11 

133 
26 



0-2 

trace 
trace 



1-2 



100 



100 



* It dissolves in 48 times its weight of water— or a gallon of water will dissolve 5 ounces 
of the Bi-carbonate containing 1 3-5 ounces of magnesia. 



UMLIKE EFFECTS OF DIFFERENT MARLS. 



371 



The characterislic property of true marls of every variety is, I have 
said, the presence of a considerable per centaj^e of carbonate of lime iu 
the state of a fine powder, and, in general, diffused uniformly through 
the entire mass. To this calcareous matter the chief efficacy of these 
marls is no doubt to be ascribed, yet as they always contain other chemi- 
cal compounds to which the special efficacy of certain varieties has 
sometimes been ascribed, it may not be improper to direct your attention 
to the preceding table, in which the constitution of several marls, from 
different locaHties, is represented, after the analyses of Sprengel. 

Several reflections will occur to you on looking at these tables — such as 

First — that marls differ very much in composition, and therefore 
must differ \^ery much also in the effects which they are capable of pro- 
ducing when applied in the same quantity to the same kinds of land. 

Second — that, among other differences, the proportion of carbonate of 
lime is very unlike — in some varieties amounting to 85 lbs. out of every 
hundred, while in others as little as 5 lbs. are present in the same weight. 
You will understand, therefore, how very diiFerent the quantity applied 
to the land must be, if these several varieties are to produce an equal 
liming or to add equal quantities of lime to the soil. You will see that 
each of three persons may be adopting the best practice with his own 
marl — though the one add only 12 to ^0 tons per acre, while the second 
adds 50 to 60, and the third 100 to 120 tons. 

Third — that the proportion of phosphate of lime (bone-earth) is in 
some marls considerably greater than in others. Thus with every ton 
of the first of the above marls you would la}'- on the soil 52 lbs. of bone 
earth — about as much as is contained in a cwt. of bone-dust — while with 
the second you would only add 11 lbs. In so far as their effects upon the 
land depend, or are influenced by the presence of this substance, there- 
fore, they must also be very different. And 

Fourth — that the mechanical affects of these marls upon the soil to 
which they are added must be very unlike, since some contain 70 or 80 
lbs. of sand in every hundred — while others contain a considerable 
quantity of clay. The opening effects of the one marl, and the stiffen- 
ing effects of the other, when they are laid on in large quantities, con- 
not fail to produce very different alterations in the physical characters of 
the soil. 

2°. Shell Sand. — The sands that skirt the shores of the sea are found 
in many localities to be composed, in large proportion, of the fragments 
of broken aud comminuted shells. These form a calcareous sand, 
mixed occasionally with portions of animal matter, and, when taken 
fresh from the sea-shore, with some saline matter derived from the sea. 

Such is the case in many places on the coast of Cornwall. From 
these spots the sand is transported to a distance of many miles into the 
interior for the porpose of being laid upon the land. It has been esti- 
mated* that seven millions of cubic feet are at present employed every 
year in that county for this purpose. 

On the western coast of Scotland also, and on the shores of the island 
of Arran and of the Western Isles, this shell sand abounds, and is 
applied extensively, and with remarkably beneficial effects, both to the 

' De la Beche's Geological Report on Cornwall, ^c, p. 480.^ 



372 COMPOSITION OF SHELL AND CORAL LANDS. 

pasture lands and to the peaty soils that cover so large an area in this 
remote part of Scotland. It is chiefly along the coasts that it has hith- 
erto been extensively employed, and it is transported by sea to a dis- 
tance of 80 or 100 miles. "In the island of Barray alone, there are 
four square miles of shells and shell sand of the finest quality and of an 
indefinite depth."* When covered with a dressing of this shell sand the 
peaty surface becomes covered with a sward of delicate grass — and the 
border of green herbage that skirts the shores of these islands in so 
many places is to be ascribed either to the artificial application of such 
dressing or to the natural action of the sea winds in strewing the fine 
sand over them, when seasons of storm occur. 

The coasts of Ireland is no less rich in such sand in many parts both 
of its northern and southern coasts. A century and a half a;;0, it is 
known to have been used for agricultural purposes in the north of Ireland 
— and nearly as longago to have been brought over to the opposite (Gal- 
loway) coast of Scotland with a view of being applied to the land (Mac- 
donald). In the south, according to Mrs. Hall,f the coral sand raised 
in Bantry Bay alone produces c€4000 or c£5000 a-year to the boatmen 
who procure it and to the peasants who convey it up the country. 

On the coast, of France, and especially in Britany, opposite to Corn- 
wall, on the other side of the English channel, it is obtained in large 
quantity, and is in great demand.} It is applied to the clay soils and to 
marshy grass lands with much advantage, and is carried far inland for 
this purpose. It is there called trez, and is laid on the land at the rate 
of 10 to 15 tons per acre. On the southern coasts of France, where shell 
sand is met with, it is known by the name oftanque or tangue. 

The shell sand of Cornwall contains from 40 to 70 per cent, of carbo- 
nate of lime, with an equally variable small admixture of animal mat- 
ter and of sea salt. The rest is chiefly siliceous sand. Other varieties 
have a similar composition. Two specimens of iangue from the south 
of France, analysed by Vitalis, and one of shell sand from the island 
of Isla, partially examined by myself, consisted of 

Tangue from the Shell Sand 

South of France. from Isla. 

Sand, chiefly siliceous .... 20*3 40 ? m « * oc « 

A 1 • ^ r\ ■^ c T A c A a t ' 1'7 tO 65-7 

Alumina and Oxide of Iron . . . 4*6 4-6 ^ 

Carbonate of Lime 66-0 47-5 28 to 34 

Phosphate of Lime ? ? 0-3 

Water, and loss 9-1 7-9 — 



100 100 100 

3°. Coral sand is similar in its nature to the shell sand with which it 
is often intermixed on the sea-shore. It is collected in considerable 
quantities, however, by the aid of the drag — being torn up by the fisher- 
men in a living state — on the coasts of Ireland (Bantry Bay and else- 
where), and on the shores of Britany, especiallv near the mouths of the 
rivers. In this fresh state it is preferred by the farmer, probably because 
it contains both more saline and more animal matter. This animal 

* '^l-i.cilonaAiVs Agricultural Survey of the Hebrides^ p. 401. 

t Mrs. Hall's Ireland. 

X Payen ^nJ Boussin^ault. Annates de Chim. et de Phys., third series, in., p. 92. 



USE OF LIME-STONE SAND AND GRAVEL. 373 

matter enables it to unite in some measure the beneficial effects which 
follow from the application of marl and of a small dressing of farm- 
yard or other valuable mixed manure. 

Payen and Boussingault ascribe the principal efficacy of the shell 
and coral sands to the small quantity of animal matter which is present 
in them. These chemists estimate the relative manuring powers of 
different substances applied to the land by the quantitiesof nitrogen which 
they severally contain, and thus, compared with farm-yard manure, 
attribute to the shell and coral sands the following relative values : — 

Contain of Relative 

Nitrogen. values. 

100 lbs. of Farm-yard Manure 0-40 lbs. 100 

do. of Coral Sand (Merl) 0-512 lbs. 128 

do. of Shell Sand {Trez) 0-13 lbs. 32^* 

That is to say, that, in so far as the action of these substances is de- 
pendent upon the nitrogen they contain, fresh coral sand is nearly one- 
third more valuable than farm-yard manure, while fresh shell sand is 
only equal in virtue to one- third of its weight of the same substance. 

Though, as I have already had frequent occasion to observe to you, 
much weight is not to be attached to such methods of estimating the 
relative values of manuring substances by the proportions of any one 
of the ingredients they happen to contain — yet the fact, that so much 
animal matter is occasionally present in the living corals, accounts in a 
satisfactory manner for the immediate effects of this form of calcareous 
application. This animal matter acts directly and during the first year ; 
the carbonate of lime begins to shew its beneficial influence most dis- 
tinctly when two or three years have passed. 

4°. Lime-stone Sand and Gravel. — In countries which abound in 
lime-stones, there are found scattered here and there, in the hollows and 
on the hill sides, banks and heaps of sand and gravel, in which rounded 
particles of lime-stone abound. These are distinguished by the names of 
lime-stone sand and gravel, and are derived from the decay or wearing 
down of the lime-stone and other rocks by the action of water. Such 
accumulations are frequent in Ireland. They are indeed extensively 
diffused over the surface of that island, as we might expect in a country 
abounding so much in rocks of mountain lime-stone. In the neighbour- 
hood of peat bogs these sands and gravels are a real blessing. They 
are a ready, most useful, and largely employed means of improvement, 
producing, upon arable land, the ordinary effects of liming, and, when 
spread upon boggy soils, alone enabling it to grow sweet herbage and to 
afford a nourishing pasture. The proportion of carbonate of lime these 
sands and gravels contain is very variable. I have examined two va- 
rieties from Kilfinane, in the county of Cork(?). The one, a yellow 
sand, contained 26 per cent, of carbonate of lime — the residue, being a 
fine red sand, chiefly siliceous ; the other, a fine gravel of a grey colour, 
contained 40 per cent, of carbonate of lime in the form chiefly of rounded 
fragments of blue lime-stone, the residue consisting of fragments of 
sand-stone, of quartz, and of granite. 

The application of such mixtures must not only improve the physical 
characters of the soil, but the presence of the fragments of granite, 

• Annalesde Chim. etdePhys., third series, in., p. 103. 



374 CRUSHED L^JIE-STONES. EFFECTS OF MARLS. 

con(ainin.£( undecom posed felspar and mica (Lee. XII., § 1), must con- 
tribute materially to aid the fertilizing action of the lime-stone with 
which they are mixed. 

5°. Crushed Lime-stone. — The good effects of calcareous marls and 
of lime-stone gravels naturally suggest the crushing of lime-stones as a 
means of obtaining carbonate of lime in so minute a state of division 
that it may be usefully applied to the soil. Lord Kames was, I believe, 
the first who in this country endeavoured to bring this suggestion into 
practical operation. He is said to have caused machinery to be erected 
for the purpose in one of the remotest districts of Scotland, but from 
some cause the plan seems never to have obtained a proper trial. 

One of the results which, as we have already seen, follows from the 
burning of rich lime is this, that it naturally falls to a very fine powder 
as it slakes. Where coal or other combustible is cheap, therefore, it 
may possibly be reduced to a fine powder by burning, at a less Cost than 
it could be crushed. 

Yet there are two cases or conditions in which crushing might be re- 
sorted to with equal advantage and economy. 

First, where coal is dear or remote, while lime-stones and water power 
are abundant. There are many inland districts in each of the three 
kingdoms where these conditions exist, and in which, therefore, the 
erection of cheap machinery might afford the means of greatly fertiliz- 
ing the land; and 

Second. — There are in many localities rocks rich in calcareous matter, 
which are nevertheless so impure, or contain so much other earthy mat- 
ter, that they cannot be burned into lime. Yet, if crushed, these same 
masses of rock would form a valuable dressing for the land. Many 
lime-stones of this impure character, which are really useless for build- 
ing purposes — which do not fall to powder when burned, and which 
have, therefore, been hitherto neglected as useless — might, by crushing, 
be made extensively available for agricultural purposes. The siliceous 
lime-stones (corn-stones) of the old red sand-stone, the earthy beds of 
the mountain lime-stone, and many of the calcareous strata of the Silu- 
rian system might thus be made to improve more extensively the lo- 
calities in which they are severally met with. The richer limes now 
brought from a great distance, and at much expense — as on the Scottish 
borders — might be in a great measure superseded by the native produce 
of the district. 

§ 6. Effects of marl and of the coral, shell, and lime-stone sands^ upon 

the soil. 

The effects which result from the application of the above natural 
forms of carbonate of lime are of two kinds. 

1°. TheAr physical effect in altering the natural texture of the soils to 
which they are added. This effect will necessarily vary with the nature 
of the earthy matter associated with the lime. Thus the clay marls 
will improve, by stiffening, such soils as are light and sandy — the; 
shell sands and lime-stone-gravels, by opening and rendering more free] 
and easier worked such soils as are stiff", intractable, and more or lessj 
impervious — while either will impart solidity and substance to such as 
are of a peaty nature or over-bound with other forms of vegetable matter. 



OBSERVED EFFECTS OF MARLS. 375 

2'^. Their chemical effect in actually rendering the soil productive of 
larger crops. This effect is altogether independent of any alteration in 
the physical properties of the soil, and is nearly the same in kind, what- 
ever be the variety of marl, <5cc., we apply. It differs in degree, chiefly 
according to the proportion of calcareous matter which each variety 
contains. This action of the pure carbonate of lime they contain is 
supposed to be modified in some cases by the proportion of phosphate of 
lime, (fee. (p. 370) with which it may be mixed — it is certainly modified 
by the animal and saline matters which are present in the recent corals 
and shell sands. 

The several effects of marls and calcareous sands being dependent 
upon circumstances so different, it is not surprising that the opinions of 
practical men should, in former times, have been divided in regard to the 
action of this or that marl upon their respective soils. In no two localities 
was the substance applied to the land exactly alike, and hence unlike re- 
sults must necessarily have followed, and disappointment been occasion- 
ally experienced from their use. And yet the importance of rightly under- 
standing the kind and degree of effect which these manuring substances 
ought to produce may be estimated from the fact, that a larger surface of 
the cropped land in Europe is improved by the assistance of calcareous 
marls and sands — than by the aid of burned lime and of farm-yard ma- 
nure put together. 

It is not easy in any case to estimate with precision what portion of 
the effect caused by a given marl is due to its chemical and what to its 
physical action. Even the pure limes, when applied in large doses, 
produce a change in the texture of the soil, wliich on stiff" lands is bene- 
ficial, and on light or sandy fields often injurious. In all cases, there- 
fore, the action of lime applied in any form may be considered as partly 
physical and partly chemical — the extent of the chemical action in 
general increasing with the proportion of lime which the kind of cal- 
careous matter employed is known to contain. 

The observed effects of marls and shell sands, in so far as they are 
chemical, are very analogous to those produced by lime as it is generally 
applied in the quick or slaked state in so many parts of our islands. 

They alter the nature and quality of the grasses when applied to 
pasture — they cover even the undrained bog with a short rich grass— 
they extirpate heath, and bent, and useless moss — they exterminate 
the weeds which infest the unlimed corn fields — they increase the 
quantity and enable the land to grow a better quality of corn — they ma- 
nifest a continued action for many years after they have been applied — 
like the purer limes they act more energetically if aided by the occa- 
sional addition of other manure — and like them they finally exhaust* 
a soil from which the successive crops are reaped, without the requisite 
return of decaying animal or vegetable matter. 

But to these and other effects I shall have occasion to draw your 
attention more particularly in a subsequent part of the present lecture. 

§ 7. Of the use of chalk as a manure. 
Chalk is another form of carbonate of lime which occurs very abun- 

• Of shell marl the same quantity exhausts sooner than clay marl (Karnes). This is owing 
chiefly to the larger proportion of hme contained in the former. 
32 



376 OF THE USE OF CHALK AS A MANURE. 

dantly in nature, and which, from its softness, has in many parts of 
Enfi;land been extensively applied to the land in an unburned state. 

The practice of chalking prevails more or less extensively in all that 
part of England (Lee. XI., § 8), over which the chalk formation ex- 
tends. It is usually dug up from pits towards the close of the autumn 
or the beginning of winter, when full of water, and laid upcn the land 
in heaps. During the winter's frost the lumps of chalk fall to pieces, 
and are readily spread over the fields in spring. The quantity laid on 
varies with the quality of the soil and of the chalk itself, and with the 
more or less perfect crumbling it undergoes during the season of winter, 
and with the purpose it is intended to serve. It gives tenacity and 
closeness to gravelly soils,* opens and imparts freeness to stifFcIays, and 
adds firmness to such as are of a sandy nature. 

If a physical improvement of this kind be required, it is laid on at the 
rate of from 400 to 1000 bushels an acre. But some chalks contain 
much more clay than others, and are employed, therefore, in smaller 
proportions. 

For the improvement of coarse, sour, marshy pasture, it is applied at 
the rate of 150 to 250 bushels an acre, and speedily brings up a sweet 
and delicate herbage. It is also said to root out sorrel from lands that 
are infested with this plant. 

These effects are precisely such as usually follow from the applica- 
tion of marl, and, like marl, the repetition of chalk exhausts the land, if 
manure be not afterwards added to it in sufficient quantity. 

But the chalking of the Southern Downs and of the Wolds of Lin- 
colnshire and Yorkshire would appear to differ in some respects from 
ordinary marling. On the thin soils immediately resting upon the 
chalk, experience has shown that repeated dressings of chalk re- 
cently dug up, may be applied with much benefit. To a stranger, 
also, it appears singular that an admixture of that chalk which 
lies immediately beneath the soil is not productive of the same ad- 
vantage. Even the chalk of an entire district is, in some cases, rejected 
by the farmer, and he will rather bring another variety from a consi- 
derable distance, than incur the less expense of laying on his land that 
which is met with on his own or on his neighbours' farms. Thus the 
Suffolk farmers prefer the chalk of Kent to lay on their lands, and are at 
the cost of bringing it across the estuary of the Thames, though chalk 
rocks lie alnnost every where around and beneath them. 

The cause of the diversities which thus present themselves in the 
practice of experienced agriculturists is, partly at least, to be sought for 
in'the qualities of the different varieties of chalk employed. Careful 
analyses have not yet shown in what respects these chalks differ in che- 
mical constitution, and until this is ascertained we must remain in some 
measure in the dark, both as to the way in which a dressing of chalk 
acts in improving a soil already rich in chalk, and why chalk from one 
locality should act so much more beneficially than another. 

With one thing, however, we are familiar, that the upper beds of 
chalk abound in flint, and where they form the surface support a thin 
and scanty herbage — while the under chalks are more tenacious and 

* Mr. Gawler, North Hampshire, states that a gravel thus stiffened, instead of 12 to 16 
bushels of wheat, j-ielded afterwards 24 to 30 bushels.— British Husbandry, i., p. 260. 



EFFECTS OP CHALK ON THE WOLDS. 27'f 

apparently more rich in clay, and support e^enerally a soil which yields 
valuable crops of corn. An admixture of the lower, therefore, ought to 
improve the soils of the upper; and as the chalks of Kent consist of 
these lower beds, we can understand why the practical farmer in Suffolk 
should prefer them to the upper chalks of his own neighbourhood. Still 
we cannot, as yet, give the scientific reasons why the one chalk should 
be better than the other. A. rigorous chemical analysis can alone deter- 
mine with certainty why the one should produce a different efTect from 
the other. 

Chalks may diflTer in the proportion of clay or of organic matter with 
which they are associated — in the quantity of silica (the substance of 
flints) or of silicates they contain, — in the amount of magnesia or of 
phosphate of lime which can be detected in them — or of saline matter 
which a careful examination will discover, — and they may even differ 
physically in the fineness of the ultimate particles of which the substance 
of the chalk is composed.* All such differences may modify the action 
of the several varieties in such a way as, when accurately investigated, 
to enable us to account for the remarkable preference manifested by 
practical men for the one over the other. Until such an investigation 
has been carefully made, it is unfair hastily to class among local preju- 
dices what may prove to be the results of long practical experience. 

On the chalk Wolds of Lincolnshire and Yorkshire the practice of 
chalking even the thin soils is now comparatively old in date. The 
lowest chalks are there also much preferred, — they are laid on at the rate 
of 60 to 80 cubic yards per acre, and they cause a great improvement, 
especially upon the deep lands, as they are called, where the soil is 
deepest. Corn does not yield so well, nor ripen so early, on these deep 
soils, as where a thinner covering rests upon the chalk. It is naturally 
also unfit for barley or turnips, the latter plant being especially infested 
with the disease called fingers and toesf (Strickland). But a heavy 
chalking removes all the above defects of these deep soils, and for a 
long period of time. The corn ripens sooner, is larger in quantity, and 
better in quality, and the turnips grow perfectly free from disease. 

These, however, are to be regarded as only the usual effects of a large 
addition of lime to a soil in which previously little existed. It is a fact 
which will naturally strike you as remarkable, that soils which rest 
upon chalk, as well as upon other lime-stone rocks, even at the depth of 
a few inches only, are often, and especially when in a state of nature, 
so destitute of lime that not a particle can be detected in them. That 
lime in any form should benefit such soils is consistent with uniform 
experience. I shall presently have an opportunity of directing your 
attention to the two concurring causes by the joint operation of which 
lime is sooner or later wholly removed from the soil, even where, as in 
the Wolds, it rests immediately upon the chalk. 

§ 8. Is lime indispensable to the fertility of the soil ? 
It is the result of universal experience wherever agriculture has been 

* Ehrenberor has discovered (hat chalk is in a great; measure composed of the skeletons, 
shells, or other exuvial (spoils) of n\arine microscopic animals. 

f BriCish Husbandry, iti., p. 124. 



378 I.I ME tVLWAYS PRESE^'T IIS FERTILE SOILS. 

advanced to the state of an art, that the presence of lime is useful to 
the soil. 

Not only is this fact deduced from the result of innumerable applica- 
tions of this substance to lands of every quality, but it is established also 
by a consideration of the known chemical constitution of soils which are 
naturally possessed of unlike degrees of fertility. 

Thus sandy or siliceous soils are more or less barren if lime be ab- 
sent — while the addition of this substance in the form of marl or other- 
wise renders them susceptible of cultivation. So clay soils, in which 
no lime can be detected, are often at once changed in character by a 
sufficient liming. Felspar soils contain no lime, and they are barren — 
and the same is true of such as are derived immediately from the de- 
gradation of the serpentine rocks. 

Trap soils, on the other hand — such as are derived from decayed 
basalts or green-stones — are poor in proportion as felspar abounds in 
them. Where augites and zeolites are present in large proportion in 
the trap from which they are formed, the soils are rich, and may even 
be used as marl. The only difference in this latter case is, that lime is 
not deficient (Lee. XII., § 4), — and to this difference the greater fertility 
may fairly be ascribed. 

But let it be conceded that lime is useful to or benefits the soil in 
•which it exists, you may still ask — is lime indispensable to the soil ? — 
is it impossible for even an average fertility to be manifested where 
lime is entirely absent ? 

There are two different considerations, from each of which we may 
deduce a more or less satisfactory answer to this question. 

1°. The results of all the analyses hitherto made of soils naturally 
fertile show that lime is universally present. The per-centage of lime 
in a soil may be very small, yet it can always be detected when valua- 
ble and healthy crops will grow upon it. Thus the fertile soil of the 

Marsh lands in Holstein contains 0*2 per cent, of carbonate of lime. 

Salt Marsh in East Friesland 0-6 " " 

Rich pasture near Durham . 1-31 " " 

But though the per centage of lime in these cases appears small, the 
absolute quantity of lime present in the land is still large. Thus sup- 
pose the first of these soils, which contains the least, to be only six 
inches in depth, and each cubic foot to weigh only 80 lbs. — it would 
contain about 3500 lbs. of carbonate of lime, upwards of a ton and a 
half, in every acre. And this lime would be intimately mixed with the 
whole soil, in which state it is always most effective in its operation. It 
may also be inferred with safety that if the upper six inches contained 
this proportion of lime, the under soil would probably be richer still, 
since lime tends not so much to diffuse itself through, as to sink down- 
wards into the soil. 

2°. The results of all the chemical examinations hitherto made in 
regard to the nature of the inorganic matter contained in the sap and 
substance of plants indicate, — if not the absolute necessity of lime to the 
growth of plants, — at least that in nature all cultivated plants do ab- 
sorb it by their roots from the soil, and make use of it in some way in 
aid of iheir growth. In so far as our practice is concerned, this is very 
much the same as if we could prove lime to be absolutely indispensable. 



STATE IN WHICH LIME EXISTS IN THE SOIL. 379 

The ash of the leaf and bulb of the turnip or potatoe, of the grain 
and straw of our corn-bearins; plants, and of the stems and seeds of our 

A 1 

grasses, all contain lime whenever and wherever they are grown. And 
most of them attain high health and luxuriance only where lime is 
easily attained. 

Grant, then, that lime appears to be, perhaps virtually is, a necessary 
food of plants, without which their natural health cannot be maintained, 
nor functions discharged, — still the quantity which must be present in 
the soil to supply this food is not necessarily large. Even in favour- 
able circumstances we have seen (Lee. X., § 3) that the average crops 
during an entire rotation of four years may not carry off more than 250 
lbs. of lime from the acre of land, a quantity which even the marsh 
soils of Holstein would be able to supply for half a century, could the 
roots readily make their way into every part of the soil. 

Still we may safely hold, 1 think, that this quantity of lime at least 
is indispensable — if cultivated plants are to flourish and ripen. So 
much, at least, must in practice be every year added to cultivated land 
in one form or another, where the crops are in whole or in part carried 
otfthe land. Where it is not added either artificially or by some natu- 
ral 'process, infertility must gradually ensue. We shall presently see 
that lime has other functions to perform in the soil, and that there are 
natural causes in constant operation in our climate which render a 
larger addition than this desirable at least, if not indispensable to con- 
tinued fertility. 

§ 9. State of combination in which lime exists in the soiU 

This lime, which we have concluded to be an indispensable constitu-^ 
ent of fertile soils, may be present in several distinct states of combina- 
tion. 

1°. In that of chloride of calcium. — This compound, as we have al- 
ready seen (Lee. IX., § 4), is very soluble in water, and is not unfre- 
quently to be detected in the sap, especially of the roots of plants. Its 
solubility, however, exposes it to be readily washed out of the soil by 
the rains, and perhaps for this reason it is not one of those forms of com- 
bination in which lime is recognised as a uniform or necessary consti- 
tuent of the soil. Its presence may be detected by boiling half a pound 
of the soil in distilled water, filtering and evaporating the solution to 
dryness. If the dry mass become moist on exposure to the air, and if, 
after being dissolved in water, it give a white precipitate with oxalate 
of ammonia, and after being rendered sour by a few drops of nitric acid, 
a white precipitate again with nitrate of silver, it may be inferred to 
contain chloride of calcium. 

2=*. In that of sulphate of lime or gypsum. — In this state also it is not 
a constant, and in a few cases only an abundant, constituent of the soil. 
Its presence may be detected by the deposition of minute crystals on the 
sides of the vessel during the evaporation of the solution obtained by 
boiling the soil in distilled water. Or, its presence may be inferred if, 
after observing that oxalate of ammonia causes a precipitate in one 
small portion of the solution, it be found that nitrate of baryta also 
throws down a white precipitate from another small portion, 
32* 



380 HUMATE OF LIME IN THE SOIL. 

3°. In the state of phosphate. — This compount! is probably present, 
though always in small proportion, in every soil which is capable of 
raising a nutritious vegetation. It may be readily detected by treating 
500 grains of the dry soil for 12 hours with dilute muriatic acid, and oc- 
casio^nally stirring. If to the fihered solution^caustic ammonia be add- 
ed, a brownish precipitate will usually fall. If this precipitate be se- 
parated, and treated with acetic acid (vinegar), it will all dissolve if no 
phosphoric acid be present. If this experijHreiTt^be carefully performed, 
and a residue remain undissolved, the presence of phosphoric acid in 
the solution, and of phosphate of Hme in the soil, may be safely in- 
ferred. 

4°. In the state of silicate, lime rarely exists in the soil in any con- 
siderable quantity. It is chiefly in such as are derived from the decay 
of the trap rocks or of some varieties of granite (Sienite), that silicate of 
lime is to be expected to occur. 

If, after being treated with dilute sulphuric acid, as above described, 
the soil be digested for some hours at a gentle heat with concentrated 
muriatic acid — a solution will be obtained from which ammonia will 
again throw down a brown precipitate. If oxalate of ammonia now 
cause a white precipitate of oxalate of lime, and if, on evaporating to 
dryness, the solution leave a portion of silica insoluble in acids, we may 
infer that the soil most probably contains some lime in the state of sili- 
cate. 

5°. In the state of carbonate, lime is generally supposed most usually 
to exist, and most abundantly in all soils. If on pouring dilute muri- 
atic acid upon a soil, a visible effervescence or escape of minute bubbles 
of gas manifest itself, or if, when the experiment is made in a tube 
closed at one end, and inverted over water or mercury, bubbles of gas 
collect in the upper end of the tube — the soil contains some carbonate. 
If after ammonia has been added to the solution, oxalate of ammonia 
throws down a white precipitate of oxalate of lime — the soil contains 
carbonate of lime. 

G°. In the state of humate. — In combination with humic acid (Lee. 
XIII., § 1,) lime exists most frequently in soils which abound in vegetable 
matter — in peaty soils, for example, to which quick-lime or marl of any 
kind have been added for the purpose of agricultural improvement. 
The presence of lime in the state of humate is only to be detected by 
carefully determining the relative weights of the carbonic acid given off 
during the action of dilute muriatic acid upon the soil, and of the lime 
contained in the solution thus obtained.* If for every 100 grains of 
carbonic acid there be more than 77-24 grains of lime, the remainder or 
excess has existed in the soil in combination with humic or some analo- 
gous organic acid.f 

Few investigations have as yet been made in regard to the proportion 
of lime which exists in the soil in the state of humate. It has generally 
been taken for granted — either that a soil was destitute of lime if it exhi- 

• Bee Appendix. 

t To such analogous acids belong the crenic and apocrenic acids (Lee. XIIL, § 1.). The 
existence of these acids in the soil is by no means problematical. According to Professor 
Hermann, of Moscow, they exist in the rich black soil (Tchornoi Zem.) of Little Russia, to 
the amount of 4 per cent. ... 



QUANTITY OF LIME TO BE APPLIED TO THE SOIL. 381 

bited no sensible effervescence with dilute muriatic acid, — or when tur- 

iher research was made, and the quantity of lime taken up by this acid 

rigorously determined, that the whole of this lime must have existed in 

tlfe soil in the state of carbonate. That this is not necessarily the case, 

however, appears to be proved by some recent examinations of certain 

soils in Normandy, which contain as much as 14 to 15 per cent, of lime, 

and yet exhibit no effervescence, and contain no carbonate. The whole 

of the lime is said to be in the state of humate. 

M. Dubuc, who has published the analyses of these soils, attributes 

much of their fertility to the presence of the humate of lime. Thus he 

says that the soils of 

Containing per cent. 
Of Cdrbonate. Of Humate. Yields of Wheat. 

Lieuvin, Neubourg, and Sistot, 18 to 20 12 to 15 fold. 

Pavilli 5 8 to 10 " 

BleviUe 24 8 to 10 " 

Clay of Ouche 1 4 to 5 " 

The first two yielding a wheat crop every second year, the third only at 
longer intervals. 

Whatever degree of influence on the fertility of the soil it may ap- 
pear proper to attribute to the existence of lime in the soil in the state 
of humate, it is manifestly of some importance that its presence in this 
state of combination should be more frequently and more carefully- 
sought after. 

The only one of the above compounds which is usually added to the 
land, for the purpose of producing the ordinary effects of lime, is the 
carbonate. Gypsum is applied only in small quantity for certain spe- 
cial purposes, and does not always produce a sensible effect. It is inca- 
pable, therefore, of performing those purposes in the soil which are 
served either by quick-lime or by the carbonate. The humate of lime 
is probably formed in our lime composts, especially when much vegetable 
matter is contained in them, and may thus be not unfrequently applied 
directly to the land. 

§ 10. Of the quantity of lime which, ought to be added to the soil. 

The quantity of lime which ought to be added to the soil is dependent 
upon so many circumstances, that it is impossible to state any general 
rule by which, in all cases, the practical man can safely regulate his 
procedure. 

1°. To soils which contain no lime, or to which it is added for the first 
time, a larger dose must be given. 

We have seen that a certain rninimum portion of lime is indispensable 
to a productive soil. If we suppose this smallest quantity to be no 
greater than in the surface of the marsh lands of Holstein (p. 378), — 
tlien with a soil six inches in depth — which contains no lime, we ought to 
mix a ton and a half, say 40 bushels of slaked lime, and by successive 
yearly additions to supply the annual waste. 

But to mix this feeble dose of lime intimately with the soil to a depth 
of six inches would obviously require an expenditure of labour which 
the practical farmer could rarely afford. It would be greater economy, 
therefore, in most cases to add a dose several times larger, and this not 



382 MORE OUGHT TO CE LAID ON CLAY, WET, AND MARSHY SOILS, 

only because the same amount of labour would diffuse it more generally 
throuf^h the whole soil, but because this larger liming would render less 
necessary the immediate addition of new supplies to repair the una- 
voidable waste. 

But there is reason to believe that the proportion of lime which the soil 
ought to contain, if it is to be successfully subjected to arable culture, 
ought to be much larger than is above assumed as the smallest or mini- 
mum quantity. If we suppose one per cent, to be necessary, then 
eight tons of lime-shells, or upwards of 300 bushels of slaked lime, must 
be mixed with a soil six inches in depth, to impart to it this proportion — 
or half the quantity if it be kept within three inches of the surface. 
Even a very large dose of lime, therefore, does not, if it be well mixed, 
materially alter the constitution of the soil. 

2°. But experience has proved that the quantity of lime which a 
skilful farmer will add to his land will vary with many other circumstan- 
ces besides the depth of his soil, and the proportion of lime it already 
contains. Thus — 

a. On clay lands more lime is necessary than on light and sandy soils. 
This may be partly ascribed to the physical effect of the lime in opening 
and loosening the stiff' clay — but independent of this action the parti- 
cles of lime are liable to be coated over and enveloped by the fine clay, 
and thus shut out from the access of the air. These particles, therefore, 
must be more numerous in such a soil if as many of them are to be ex- 
posed to the air as in lighter land, through which the atmospheric air 
continually permeates. 

h. On wet and marshy soils, a larger application still may be made 
whh safety, and partly for the same reason. 

The moisture surrounding the lime shuts out the air, without the 
ready access of which lime cannot perform its important functions. 
The same moisture tends to carry down the lime and lodge it more 
speedily in the subsoil. The continued evaporation also keeps such soils 
too cold (Lee. II., § 7), to allow the chemical changes, which lime in 
favourable circumstances produces, to proceed with the requisite degree 
of rapidity. The soluble compounds which are formed as the conse- 
quence of these changes are, in wet and marshy soils, dissolved by the 
moisture, and so diluted as to enter in smaller quantity into the roots of 
plants. And lastly, in certain cases, new compounds of the lime witJi 
the earthy and stony matters of the soil are formed, which may either 
harden into visible lumps of mortar and cement, or into smaller particles 
of indurated matter, in which the lime is no longer in such a state as ta 
be able to act in an equal degree as an improver of the soil. 

In cold and wet clays, in which all these evil conditions occasionally 
meet, it is not surprising, therefore, that large doses of lime should some- 
timeshave been added without producing any sensible benefit whatever.* 

c. Again, when the soil is also rich in vegetable matter, lime may be 
still more abundantly applied. Thus, when a field is at once wet or 
marshy, and full of vegetable matter, as our peat bogs are, lime may be 
laid on more unsparingly than under any other circumstances. For in 

• "An instance is mentioneri in the Nottingham Report of 720 bushels having been laid 
on an acre of clod clay land without any benefit whatever." — British Husbandri/, i., p. 295. 



AND SUCH AS ARE RICH IN VEGETABLE MATTER. 383 

this case, besides the action of the access of water, as above explained, 
the vegetable matter combines with and masks the ordinary action of a 
considerable quantity of the lime. By this combination, no part of the 
ultimate influence of the whole lime upon the soil is necessarily lost ; 
in most cases the immediate effect only is lessened, which the same 
quantity applied to other soils would have been seen to produce. In 
favourable circumstances ils action is retarded and prolonged, the com- 
pounds it forms with vegetable matter decomposing slowly, and, there- 
fore, remaining long in the soil. 

To the exact chemical constitution of the compounds thus formed, 
as soon as lime is mixed up with a soil rich in vegetable matter, and to 
the chemical changes which these compounds gradually undergo, it will 
be necessary to direct our attention when we come to study the theory 
of the action of lime, as an improver of the soil. 

d. Not only the natural depth of the soil, as already stated, but also 
the depth to which it is usually ploughed, and to which it is customary 
to bury the lime, will materially affect the quantity which can be safely 
applied. A dose of lime which would materially injure a soil into 
which the plough rarely descends beyond two or three inches, might be 
too small an application where six or eight inches are usually turned 
over by the plough. When new soil, also, is to be brought up, which 
may be supposed to contain no lime, or in which noxious substances are 
present, a heavier dose of lime must necessarily be laid upon the land. 

3°. Such are the circumstances in which large applications of lime 
may be usefully applied to the land. In soils of an opposite character 
not only will smaller quantities of lime produce an equally beneficial 
effect, but serious injury would often be inflicted by spreading it too 
lavishly upon your fields. 

The more dry and shallow the soil, the more light and sandy, the 
less abundant in vegetable matter, the more naturally mild its locality, 
and the drier and warmer the climate in which it is situated — the less 
the quantity of lime which the prudent farmer will venture to mix with 
it. It is to the neglect of these natural indications that the exhaustion 
and barrenness that have occasionally followed the application of lime 
are to be ascribed. It is only in rare cases, such as the presence of 
much noxious mineral matter in the soil, that these indications can be 
safely neglected. 

§ 11. Ought lime to be ajjjjlied in large doses at distant intervals, or in 
smaller quantities more frequently repeated? 

The quantity of lime which ought to be applied to the land must, as 
we have seen, vary with its quality, and with the conditions in which it 
is placed. Hence the practice in this respect necessarily varies in every 
country and in almost every district. 

But a difference of opinion also prevails among practical men, as to 
whether that quantity of lime which land of a given kind may require 
ought to be applied in large doses at long intervals, or in small quantities 
frequently repeated. The indications of theory in reference to this point 
are clear and simple. 

A certain proportion of lime is indispensable in our climate to the 
production of the greatest possible fertility. Let us suppose a soil to be 



384 OUGHT LIME TO BE APPLIED IN LARGE OR SMALL DOSES. 

wholly destitute of lime — the first step of the improver would be to add 
to this indispensable proportion. This would necessarily be a large 
quantity, and, therefore, to land limed for the first time theory indicates 
the propriety of adding a large dose. 

Every year, however, a certain variable proportion of the lime is re- ' 
moved from the soil by natural causes. The effect of this removal in a 
few years becomes sensibly apparent in the diminished productiveness 
of the land. After the lapse of five or six years, during which it has 
been gradually mixing with the soil, the beneficial effects of the lime 
is generally the most striking— after this they gradually lessen, till at the 
end of a longer or shorter period, the land reverts to its original condition. 
To keep land in its best possible state^ therefore^ the natural waste ought 
from time to time to be supplied by the addition of smaller doses of lime 
at shorter intervals. 

Such is obviously the most natural coiirsd df prddedure, and he who 
farms his own estate, dnd has therefore no strong inducement to do 
otherwise,'wiil, on the fifst breaking Lip of new land, give it a heavy 
liming, and whether he afterwards retain it in arable culture or lay it 
down to grass, will at intervals of 4 to 6 years give it a new dose of one- 
fourth to one-eighth of the original quantity. But local circumstances 
and customs interfere in many well-farmed districts with this most na- 
tural treatment of the soil. In the county of Roxburgh, for example, 
on entering upon his farm, which holds on a lease cf 19 or 21 years, the 
tenant begins by liming that portion of his land which is in fallow, or 
in preparation for turnips, at the rate of 240 to 300 bushels of quick-lime 
per acre. A similar liming is given to the other portions as they come 
into fallow, so that at the end of his first rotation (4 or 5 years) the whole 
of his land has been limed at the same rate. He now continues crop- 
ping for three or four rotations (14 to 16 years), when if he is sure of re- 
maining on his farm he begins to lime again with the same quantity as 
before. If he is to quit, however, he takes the best crops he can get, 
but incurs no further outlay in the addition of lime. His successor fol- 
lows the same course — begins by expending perhaps 6£lOOO in lime, and 
before he leaves at the end of his lease, has, by continued cropping, 
brought back his land nearly to the same state in which he found it. 

In the district of Kyle and other parts of Ayrshire, again, lime is laid 
on^often when preparing for the wheat crop, either by ploughing in the 
second furrow, or by harrowing in with the seed — at the rate of 40 bushels 
of shells an acre, and this dose is of course repeated every 4 or 6 years, 
according to the length of the rotation. If we consider the probable dif- 
ference in the soil and climate, the proportion of lime added in the two 
districts does not materially differ. In Ayrshire from 8 to 10 bushels, and 
in Roxburgh from 10 to 12 bushels, are added for each year.* In both 
counties, however, many farms may be met with in which the treatment 
of the land in this respect ditTers from that which is generally followed. 
In Flanders a similar difference in the practice prevails in different 
districts. In some the land is limed only once in 12 years, in others every 

* According to General Beatson (New System of Cultivation, 1820), upwards 100 bushels 
an acre, at a cost of £7. 16s., tised to be applied to the clay lands of Sussex — on the fallow, 
1 efore wheat — every four years. This was 25 bushels per acre for each year. In such 
1 nds as these the savingfln the article of lime alone, which would follow a judicious drainage, 
vould be very great, 



COMt^AllATIVE ECONOMY OF THE TWO METHODS. 385 

third, fourth, or sixth year, according to the length of the rotation. In 
tlie former case from 40 to 50 bushels are applied per acre, in the latter 
from 10 to 12 bushels every third year. In both modes of procedure 
the quantity of lime applied by the year is nearly the same — between 
3^ and 4 bushels per acre. These quantities are very much less than 
those employed in our island, but the soils are also greatly lighter, and 
the climate, as well as the general treatment of the land, very different. 

We may consider it, therefore, as a principle recognised or involved 
in the agricultural practice both of our own and of foreign countries, 
that nearly the same annual addition of lime ought to be made to the 
land, whether it be applied at long intervals or at the recurrence of each 
rotation. There is, therefore, on the whole, no saving in the cost of lime, 
whichever method you adopt. A slight consideration of the subject, 
however, may satisfy us that there is a real difference in the compara- 
tive economy or profit of the two methods. 

Let us suppose two acres of the same clay land to be limed respec- 
tively with 200 bushels each, and that the one is cropped for twenty 
years afterwards without further liming, while the other at the end of 
every five years is dressed with an additional dose of 40 to 50 bushels. 
In both cases the land would have attained the most productive con- 
dition in five or six years. Let us suppose that in this condition it pro- 
duced annually a crop of (or equivalent in nutritive value to) 30 bushels 
of wheat, and that on neither acre did a sensible diminution appear be- 
fore the end of ten years. Then during the second ten the crops would 
gradually lessen in the one acre, while, in consequence of the re- 
addition of the lime as it disappears, the amount of produce would re- 
main sensibly the same in the other acre. Suppose the produce of the 
former gradually to diminish from 30 to 20 bushels during these ten 
years, — or that while the one has continued to yield 30 bushels during 
the whole period, the other has, on an average, yielded only 25 bushels 
during the latter ten years. If now the second large dose of 200 bushels 
be added to this latter acre, the cost of liming both will have become 
sensibly the same, but the amount of produce or of profit from the two 
acres during the second ten years will stand thus — 

10 crops, of 30 bushels efich, amount to 300 bushels. 

10 crops, of 25 bushels each, amount to 250 bushels. 



Difference in favour of frequent liming, 50 bushels per acre, 
or nearly two whole crops every lease of tweiUy years. 

Thus it appears 

1°. That, according to the practice of different countries, the quantity 
of lime which ought to be added, and consequently the cost of adding it, 
is very nearly the same, whether it be applied in larger doses at longer 
intervals, or in smttler doses more frequently repeated. 

2°. That, after the first heavy liming, the frequent application of 
small doses is the more natural method — and 

3°. That it is also the most economical or profitable method. 

It is possible that other considerations, such as the tenure by which 
your land is held, may appear sufficient to induce you to depart from 
this method ; but there seems every reason to believe that it will best 
reward those who feel themselves at liberty to follow the indications at 
once of sound theory and of enlightened practice. 



386 MANURE MUST BE ADDED WHERE LIME ABOUNDS. 

One thing, however, must be borne in mind by those who, in adopting 
the best system of hming, do not wish both to injure their land and to 
meet with ultimate disappointment. Organic matter — in the form of 
farm-yard manure, of bone or rape dust, of green crops ploughed in, or 
of peat, and other composts — must be abundantly and systematically 
added, if at the end of 20 or 40 years the land in which the full supply 
of lime is kept up is to retain its original fertility. High farming is the 
most profitable — for the soil is ever grateful for skilful treatment — but 
he who farms high in the sense of keeping up the supply of lime, must 
also farm high in the sense of keeping up the supply of organic and 
other manures in the soil — otherwise present fertility and gain will be 
followed by future barrenness and loss. If this is not to be done, it 
were better to add lime at long intervals, since as the quantity of lime 
diminishes, the land begins to enjoy a little respite, and has had time in 
some measure to recover itself — the cropping in both instances being the 
same — before the new dose is laid upon its surface.* 

§ 12. Form and state of combination in ivhich lime ought to he 
applied to the land. 

The form and state of combination in which lime ought to be applied 
to the land depend upon the nature of the soil, on the kind of cropping 
to which it is subjected, and on the special purpose which the lime is 
intended to effect. The soil may be heavy or light, in arable culture, 
or laid down to grass, and each of these conditions indicates a different 
mode of procedure in the application of lime. So the lime itself may 
be intended either to act more immediately or to be more permanent in 
its action — or it may be applied for the purpose of destroying unwhole- 
some herbage, of quickening inert vegetable matter, of generally sweet- 
ening the soil, or simply of adding to the land a substance which is in- 
dispensable to its fertility. The skilful agriculturist will modify the 
form and mode of application according as it is intended to serve one or 
other of these purposes. 

From the considerations already presented to you (§ 3) in regard to 
the changes which quick-lime undergoes in the air, it appears to be 
expedient, 

1°. To slake lime quickly, and to apply it immediately upon clay, 
boggy, marshy, or peaty lands — upon such also as contain much inert 
or generally which abound in other forms of vegetable matter. 

2°. To bents and heaths which it is desirable to extirpate, it should 
be applied in the same caustic state, or to unwholesome subsoils which 
contain much iron (sulphate of iron), as soon as they are turned up by 
the plough. In both these cases the unslaked lime-dust from the kilns 
might be laid on with advantage. 

3°. Where it is to be spread over grass lands wifhout destroying the 
herbage, it is in most cases safer to allow the lime to slake spontaneous- 

* " In the neighbourhood of Taunton, in Somersetshire, and over all the soil of the new 
red sand-stone, the farmers lime their land every time it comes in course of fallow for tur- 
nips, and this produces excellent crops, even without dung." — Morton on Soils, third edition, 
p. 181. The practical reader must not consider this custom of the Somersetshire farmers as 
at all at variance with what is slated in the text ; he must conclude, rather,— if the sentence 
here quoted is meant to apply that they lime their arable land so repeatedly, and yet add no 
organic manure — that they will, sooner or later, cease to boast of its fertility. 



COMPARATIVE ECONOMY OF LIME AND MARL. 387 

1}^ and in the open air rather than in a covered pit. It is thus obtained 
in an exceedingly fine powder, which can be easily spread, and, while 
it is sufficiently mild to leave the tender grasses unharmed, it contains 
a sufficient quantity of caustic lime (p. 368) to produce those chemical 
changes in the soil on which the efficacy of quick-lime depends. 

4*^. Where lime is applied to the fallow, is ploughed in, well har- 
rowed or otherwise mixed with the soil, it is generally of little conse- 
quence in which of the above states it is laid on. The chief condition 
is, that it be in the state of a fine powder, and that it be well spread and 
intimately mixed with the soil. Before these operations are concluded 
the lime will be very nearly in the state of combination in which it ex- 
ists in spontaneously slaked lime — whatever may have been the state 
of causticity in which it has been applied. 

You will understand that the above remarks apply only to localities 
where burned lime is usually or alone used for agricultural purposes. 
There may be localities where marl also exists, or shell or lime-stone 
sand, in greater or less abundance, and in such places it may be a ques- 
tion of some importance to determine which it would be better or more 
economical to apply. In such a case you may safely proceed upon the 
principle that the lime in the marls, &c., will ultimately produce pre- 
cisely the same effects upon your land as the lime from the kiln, provi- 
ded you lay on an equal quantity, and in an equally minute state of di- 
vision. The effect will only be a little more slow, and the full fertility 
of the land a year or two longer in being brought out. You would 
therefore consider, 

1°. How much of the marl or sand must I add to be equal to a ton of 
lime-shells? This will depend on the per-centage of lime which the 
marl contains. Suppose it to contain 20 per cent., or one-fifth of its 
weight of lime,* then five tons of the marl will be equal to one ton of 
lime shells. But as the lime in the marls and sands is never in so mi- 
nute a state of division as in the slaked Hme, the same quantity of lime 
in the former cannot be so equally diffused through the soil as in the 
latter state. An allowance must therefore be made on this account, and 
an additional quantity equal to one-fourth or one-fifth of the whole added, 
for the purpose of equalizing the efTect. 

2°. Which of the two, the quick-lime or its equivalent of marl, can 
I obtain and apply at the less cost ? This will not be difficult to calcu- 
late, the proportion of lime contained in the marl being once ascertained. 

3°. This question of economy being decided, it is necessary to consi- 
der the kind and quantity of the earthy matter with which the lime in 
the marl is mixed. If it be a lime-sand or sandy marl, it may be unfit 
10 apply to light and sandy soils ; if it be a stiff' unctuous clay marl, it 
may only render stiffer and more diffi-cult to work the clay lands on 
which you may propose to spread it. In such cases as these, however 
economical the use of marls or lime-stone sands may be, the intelligent 
farmer will prefer the addition of quick-lime wherever it is readily ac- 
cessible. 

Sussex is one of those districts in which the ancient use of marl has 

* Not carbonate of lime, but of lime in the state in which it comes from the kiln. 100 lbs. 
of carbonate contain 56 lbs. quick lime, p. 36t. 

33 



388 USE AND ADVANTAGE OF THE COMPOST FORM. 

given place to the employment of burned lime (Beatson), chiefly, I be- 
lieve, from the nature of the local marl being less adapted to the stiff 
clay lands of that county. 

§ 13. Of the use and advantage of the coyniJostform. 

As there are many cases in which lime ought to be applied unmixed 
and in the caustic state, so there are others in which it is best and most 
beneficially laid upon the land in a mild state and in the form of com- 
post. 

1°. When lime is required only in small quantities, it can be more ^ 
evenly spread when previously well mixed with from 3 to 8 times its | 
bulk of soil. 

2°. On light, sandy, and gravelly soils, when of a dry character, un- , 
mixed lime will bring up much cow-wheat {inelampyrum) and red 
poppy. If they are moist soils, or if rainy weather ensue, the lime is 
apt to run into mortar, and thus to form either an impervious subsoil, or 
lumps of a hard conglomerate, which are brought up by the plough, but 
do not readily yield their lime to the soil. These bad consequences 
are all avoided by adding the lime in the form of compost. 

3°. Applied to grass lands — unless the soil be stiff clay — or much 
coarse grass is to be extirpated, — it is generally better and safer to apply 
it in the compost form. The action of the lime on the tender herbage is 
by this means moderated, and its exhausting effect lessened upon soils 
which contain little vegetable matter. 

4°. In the compost form the same quantity of lime acts more imme- 
diately. While lying in a state of mixture, those chemical changes 
which lime either induces or promotes have already to a certain extent 
taken place, and thus the sensible effect of the lime becomes apparent 
in a shorter time after it has been laid upon the land. 

5°. This is still more distinctly the case when, besides earthy matter, 
decayed vegetable substances, ditch scourings, and other refuse, are 
mixed with the lime. The experience of every practical man has long 
proved how very much more enriching such composts are, and more ob- 
vious in their effects upon the soil, than the simple application of lime 
alone. 

6°. It is stated as the result of extended trial in Flanders and in parts 
of France, that a much smaller quantity of lime laid on in this form 
will produce an equal effect. For this, one cause may be, that the rains 
are prevented from acting upon the mass of compost as they would do 
upon the open soil — in washing out either the lime itself or the saline 
substances which are produced during its contact with the earthy and 
vegetable matter with which it is mixed. 

7°. The older the compost the more fertilizing is its action. This fact 
is of the same kind with that generally admitted in respect to the action 
of marls and unmixed lime — that it is more sensible in the second year, 
or in the second rotation, than in the first. 

In conclusion, it may be stated that this form of application is espe- 
cially adapted to the lightest and driest soils, and to such as are poorest 
in vegetable matter. In this form, lime has imparted an unexpected 
fertility even to the white and barren sands of the Landes (Puvis), and 
upon the dry hills of Derbyshire it has produced an almost equal ber'^^ 



PERIOD FOR THE APPLICATION OF LIME. 389 

§ 14. iVhen ought lime to he applied? 

This question may refer either to the period in the lease, in the rota- 
tion, or of the year in which lime may most beneficially be laid upon 
the land. We have already considered this point in so far as it refers to 
the lease, while discussing the propriety of applying lime in large or 
small doses. 

In regard to the period of the year and of the rotation, there are three 
principles by which the procedure of the practical man ought chiefly to 
be directed. 

1°. That lime takes some time to jnoduce its knoivn effects upon the soil. 
— It ought, therefore, to be applied as long as possible before the crop is 
sown. That is, in the early autumn, where either winter or spring corn 
is about to be sown, — on the naked fallow where the land is allowed to 
be at rest for a year, — or on the grass fields before breaking up, where 
the pasture is to be immediately succeeded by corn. 

2^. That quick-lime expels ammonia from decomposed and fermenting 
manure. 

When such manure, therefore, is applied to the land, as it is in all our 
well-farmed districts, quick-lime should not be so laid upon the land as 
to come into immediate contact with it. If both must be applied in the 
same year, they should be laid on at periods as distant from each other 
as may be convenient, or if this necessity does not exist, the lime should 
be spread either a year before or a year after the period in the rotation at 
which the manure is usually applied. 

It is for this reason, as well as for the other already stated (1°.) that 
lime is applied to the naked fallow, to the grass before breaking up, or 
along with the winter wheat after a green crop which has been aided by 
fermented manure. When ploughed into the fallow, or spread upon 
the grass, it has had time to be almost completely converted into the 
mild state (that of carbonate), before the manure is laid on. In this 
mild slate it has no sensible eflfect in expelling the ammonia of decom- 
posing manure. Again, when it is applied in autumn along with, or im- 
mediately before the seed, the volatile or ammoniacal part of the ma- 
nure has already been expended in nourishing the green crop, so that 
loss can rarely accrue from the admixture of the two at this period of the 
rotation. 

The excellent elementary work of Professor Lowe* contains the fol- 
lowing remark : — " It is not opposed to theory that lime should be applied 
to the soil at the same time with dung and other animal and vegetable 
substances, as is frequent in the practice of farmers." This is strictly 
correct only in regard to marls, lime-sand, &:c., or to perfectly mild lime, 
any of which may be mixed, without loss, with manure in any state. 
Of quick or caustic lime it is correct only when the animal or vegetable 
matter has not yet begun to ferment. With recent animal or vegetable 
matter quick-lime may be mixed up along with earth into a compost, 
not only without the risk of much loss, but with the prospect of mani- 
fest advantage. 

3°. That quick-lime hastens or revives the decomposition of inert or-' 
ganic matter. — This fact also indicates the propriety of allowing ih© 

• Elamenls of Practical Agriculture, third edition, p- 63. ^ 



390 LIME HASTENS ORGANIC DECOMPOSITION. 

lime as much time as possible lo operate before a crop is taken from 
land in which organic matter already abounds. Or where fermenting 
manure is added, it advises the farmer to wait till spontaneous decompo- 
sition becomes languid, when the addition of lime will bring it again into 
action and thus maintain a more equable fertility. 

In a work upon soils, which I have frequently commended to your 
notice,* you will find the following observations : — " Writers on agricul- 
ture have stated that lime hastens the decay of vegetable matter, whereas 
the fact is, that it retards the process of the decomposition of vegetable 
matter. If straw or long dung be mixed with slaked lime, it will 
be preserved ; while if mixed with an equal portion of earth, the earth 
■will hasten its decay." The two facts slated in this last sentence are, 
I believe, correct, yet it is nevertheless consistent both with theor}' and 
universal observation, that lime in the soil promotes the decomposition of 
organic matters, both animal and vegetable. This will appear more 
clearly when we come to study the precise nature of the action of lime 
upon organic substances in general. 

The above remarks, in regard to the best time for applying lime, refer 
chiefly to quick-Lime, the state in which, in England, it is so extensively 
used. Marls and shell-sands can cause no loss when mixed with the 
manure, and therefore may with safety be laid on at any period of the 
rotation. The same remark applies with greater force to the lime com- 
posts. These may be used precisely in the same way as, and even in- 
stead of, the richer manures — may be laid, without risk, upon grass lands 
of any quality, and at any period — or as a lop dressing on the young 
corn in spring, when the grass and clover seeds are sown by which the 
corn crop is to be succeeded. And as the compost acts more speedily 
than lime in any other form, it is especially adapted for immediate ap- 
plication to the crop it is intended to benefit. To wet lands also, it is 
well suited, and to such as are subject to much rain, by which, while the 
surface is naked, the soluble matters produced in the soil are likely to be 
very much washed away. 

§ 15. Of the effects produced by lime. 

The effects of pure lime upon the land, and upon vegetation, are ul~ 
timately the same, whether it be laid on in a state of hydrate or of car- 
bonate. If different varieties produce unlike effects, the quantity of 
lime applied being the same, it is because in nature lime is always more 
or less mixed with other substances which are capable of modifying the 
effects which pure lime would alone produce. The special effects of 
marls, &c., when they differ from those of burned lime, are to be ascribed 
to the presence of such admixtures. In general, however, the chemical 
action of the marls and calcareous sands is precisely the same in kind as 
that of lime in the burned and slaked state, and so far the effects which 
we have already seen to be produced by marls (p. 374), represent also 
the general effects of lime in any form. 

These general effects may be considered in reference to the land on 
which it is laid, and to the crops which are, or may he, made to grow 
upon it. 

• Morton " On Soils," third edition, p. 181. 



EFrfiCTS DiF LIME UPO>' THE LAND AND CROPS. 391 

I. EFFECTS OF LIME UPON THE LAND. 

Pure lime, like the marls, produces both a mechanical and a chemi- 
cal effect upon the soil. The former is constant with all varieties of 
tolerably pure lime, and is easily understood. It opens and renders freer 
such soils as are stiff and clayey, while it increases the porosity of such 
as are already light and sandy. To the former its mechanical action is 
almost always favourable, to the latter not unfrequently the reverse. 

From its chemical action the benefits which follow the use of lime 
are chiefly derived. These benefits are principally the following: — 

1°. It increases the fertility of all soils in which lime does not already 
abound, and especially adds to the productiveness of such as are moist 
or contain much inert vegetable matter. 

2'^. It enables the same soils to produce crops of a superior quality 
also. Land which, unlimed, will produce only a scanty crop (3 or 4 
fold) of rye, by the addition of lime alone, will yield a 6 or 7 fold re- 
turn of wheat. From some clays, also, apparently unfit to grow corn, 
it brings up luxuriant crops. 

3®. It increases the effect of a given application of manure; calla 
into action that which, having been previously added, appears to lie 
dormant; and, though as we have already seen (p. 386), manure must 
be plentifully laid upon the land, after it has been well-limed, yet the 
same degree of productiveness can still be maintained at a less cost of 
manure than where no lime has been applied. 

4°. As a necessary result of these important changes, the money 
value and annual return of the land is increased, so that tracts of coun^ 
try which had let with difficulty for 5s. an acre, have in many localities 
been rendered worth 30s. or 40s. by the application of lime alone (Sir 
J. Sinclair.) 

II. — EFFECTS OF LIME ON THE PRODUCTIONS OF THE SOIL. 

l'^. It alters the natural jy^oduce of the land, by killing some kinds of 
plants and favouring the growth of others, the seeds of which had before 
lain dormant. Thus it destroys the plants which are natural to silicious 
soils and to moist and marshy places. From the corn-field it extirpates 
the corn-marigold {chrysanthemum, segetum),* while, if added in excess, 
it encourages the red poppy, the yellow cow-wheat {melampyrum pra- 
tense), and the yellow rattle {rhinanthus crista galli), and when it has 
sunk, favours the growth of the troublesome and deep-rooted coltsfoot. 

Similar effects are produced upon the natural grasses. It kills heath, 
moss, and sour and bentyf {agrostis) grasses, and brings up a sweet 
and tender herbage, mixed with white and red clovers, more greedily 
eaten and more nourishing to the cattle. Indeed all fodder, whether 
natural or artificial, is said to be sounder and more nourishing when 
grown upon land to which lime has been abundantly applied. Onbenty 
grass the richest animal manure often produces little improvement until 
a dressing of lime has been laid on. 

* Bijnninghausen. 

t In Lidfiisflale, on the Scottish border, is a large tract of land in what is there called 
flying benf, not worth more than 3s. an acre. If surface-drained and limed at a cost of £2. 
Ill jE J. an acre, this becomes worth 12s. {an acre for sheep pasture. An intelligent and expe- 
rienced border farmer assures me that such |and would never forget 40 to 60 bushels of lime 
per acre. a 

33* 



392 LIME IMrROVES THE QUALITY OF THE CROP. 

It is partly in consequence of the change which it thus produces in 
the nature of the herbage, that the appHcation of quick-lime to old grass- 
lands, some time before breaking up, is found to be so useful a practice. 
The coarse grasses being destroyed, tough grass land is opened and 
softened, and is afterwards more easily worked, while, when turned 
over by the plough, the sod sooner decays and enriches the soil. It is 
another advantage of this practice, however, that the lime has time* to 
diffuse itself through the soil, and to induce some of those chemical 
changes by which the succeeding crops of corn are so greatly benefitted. 

2°. It improves the quality of almost every cultivated crop. Thus, 
upon limed land, 

a. The grain of the corn crops has a thinner skin, is heavier, and 
yields more flour, while this flour is said also to be richer in gluten. 
On the other hand, these crops, after lime, run less to straw, and are 
more seldom laid. In wet seasons (in Ayrshire) wheat preserves 
its healthy appearance, while on unlimed land, of equal quality, 
it is yellow and sickly. A more marked improvement is said also to be 
produced both in the quantity and in the quality of the spring-sown 
than of the winter-sown crops (Puvis.) 

h. Potatoes grown upon all soils are more agreeable to the taste and 
more mealy after lime has been applied, and this is especially the case 
on heavy and wet lands, which lie still undrained. 

c. Turnips are often improved both in quantity and in quality when 
it is laid on in preparing the ground for the seed. It is most efficient, 
and causes the greatest saving of farm-yard manure where it is applied 
in the compost form, and where the land is already rich in organic mat- 
ter of various kinds. 

d. Peas are grown more pleasant to the taste, and are said to be 
more easily hailed soft. Both beans and peas also yield more grain. 

c. RajJe, after a half-liming and manuring, gives extraordinary crops, 
and the same is the case with the colsa, the seed of which is largely 
raised in France for the oil which it yields. 

/. On Jlax alone it is said to be injurious, diminishing the strength of 
the fibre of the stem. Hence, in Belgium, flax is not grown on limed 
land till seven years after the lime has been applied. 

3°. It hastens the maturity of the crop. — It is true of nearly all our 
cultivated crops, but especially of those of corn, that their full growth 
is attained more speedily when the land is limed, and that they are 
ready for the harvest from 10 to 14 days earlier. This is the case even 
with buck-wheat, which becomes sooner ripe, though it yields no larger 
a return, when lime is applied to the land on which it is grown. 

4°. The liming of the land is the harbinger of health as well as of 
abundance. It salubrifies no less than it enriches the well cultivated 
district. I have already drawn your attention (p. 310) to this as one of 
the incidental results which follow the skilful introduction of the drain 
over large tracts of country. Where the use of hme and of the drain go 
together, it is difficult to say how much of the increased healthiness of 

A compartively long period is sometime!? permitted to elapse before the grass land is 
broken up after liming. Thus at NeUierby, "lime or compost is always applied to the third 
year's pasture, which is renovated by it, and in two or three years breaks up admirably 
for oats. 



LIMK SHOULD BE KEPT NEAR THE SURFACE. 393 

the district is due to the one improvement, and how much to the other. 
The lime arrests the noxious etrluvia which tend to rise more or less 
from every soil at certain seasons of the year, and decomposes them or 
causes their elements to assume new forms of chemical combination, in 
which they no longer exert the same injurious influence upon animal 
life. How beautiful a consequence of skilful agriculture, that the health 
of the community should be promoted by the sam? methods which 
most largely increase the produce of the land ! Can you doubt that the 
All-benevolent places this consequence so plainly before you, as a stimu- 
lus to further and more general improvement — to the application of 
other knowledge still to the amelioration of the soil ? 

§ 16. Circumstances by which the effects of lime are modified. 

These effects of lime are modified by various circumstances. We 
have already seen that the quantity which must be applied to produce 
a given effect, and the form in which it will prove most advantageous, 
are, in a great measure, dependent upon the dryness of the soil, upon 
the quantity of vegetable matter it contains, and on its stiff or open tex- 
ture. There are several other circumstances, however, to which it is 
proper still to advert. Thus, 

1°. Its effects are greatest when well mixed with the soil, and kept 
near the surface within easy reach of the atmosj^here. The reason of 
this will hereafter appear. 

2°. On arable soils of the same kind and quality, the effects aro 
greatest upon such as are newly ploughed out, or upon subsoils just 
brought to day. In the case of subsoils, this is owing partly to their 
containing naturally very little lime, and partly to the presence of nox- 
ious ingredients, which lime has the power of neutralizing. In the case 
of surface soils newly ploughed out, the greater effect, in addition to 
these two causes, is due also to the large amount of vegetable and other 
organic matter which has gradually accumulated within them. It is 
the presence of this organic matter which has led to the establishment 
of the excellent practical rule — '■''that lime ought always to precede pu^ 
trescent manures ivhen old leys are broken up for cultivation.^* 

3°. Its effects are greater on certain geological formations than on 
others. Thus it produces much effect on drifted (diluvial) sands and 
clays — on the soils of the plastic and wealden clays (Lee. XL, § 8) — on 
those of the new and old-red sand-stones, of the granites, and of m.any 
slate-rocks — and, generally, on the soils formed from all rocks which 
contain little lime, or from which the lime may have been washed out 
during their gradual degradation. 

On the other hand, it is often applied in vain to the soils of the oolites 
(Lee. XL, § 8), and other calcareous formations, because of the abundance 
of lime already present in them. The advantage derived from chalking 
thin clay soils resting immediately upon the chalk rock (Lee. XL, § 
8, and page 376), is explained by the almost entire absence of lime 
from these soils. The clay covering of the chalk wolds has probably 
been formed, not from the ruins of the chalk rock itself, but from the 
deposit of muddy waters, which rested upon it for some time before 
those localities became dry land. 

4°. Lime produces a greater j^roportional improvement upon poor soils 



29-1 LAND MAT BE SATURATED WITH LIME. 

than on such as are richer (Dr. Anderson). This is also easily under- 
stood. Ii is of poor soils in their natural state of which Dr. Anderson 
speaks.* In this state they contain a greater or less quantity of organic 
inatter, but are nearly destitute of lime, and hence are in the most favour- 
able condition for being benefitted by a copious liming. Experience 
has proved that by this one operation such land may be raised in money 
value eight times, or from 5s. to 40s. per acre ; but no practical man 
would expect that arable land already worth £2. per acre could, by 
liming or any other single operation, become worth d€l6. per acre of an- 
nual rent. The greater proportional improvement produced upon poor 
lauds by lime is only an illustration, therefore, of the general truth — 
that on poor soils the efforts of the skilful improver are always crowned 
with the earliest and most apparent success. 

5°. In certain cases, ihe addition of lime, even to land in good culti- 
vation, and according to the ordinary and approved practice of the district, 
produces no effect whatever. This is sometiines observed where the 
custom prevails, as in some parts of Ayrshire and elsewhere, to apply 
lime along with every wheat crop (p. 384), and on such farms especially 
where the land is of a lighter quality. Where from 40 to 60 bushels 
of lime are added at the end of each rotation of 4 or 5 years, the land 
may soon become so saturated with lime that a fresh addition will pro- 
duce no sensible effect. Thus Mr. Cainpbell, of Craigie, informs me 
of a trial made by an intelligent farmer in his neighbourhood where al- 
ternate ridges only were limed without any sensible difference being ob- 
served. No result could show more clearly than this — that for one 
rotation at least the expense of lime might be saved, while at the same time 
the land woulfl run the less risk of exhaustion. Another fact mentioned 
by Mr. Canipbell proves the soundness of this conclusion. The lime 
never fails to produce obvious benefit where the land is allowed to be 4 
or 5 years in grass — where it is applied, that is, only once in 8 or 9 
years. The fair inference is, therefore, that in this district as well as in 
others where similar effects are observed, loo much lime is habitually 
added to the land, whereby not only is a needless expense incurred, but 
a speedier exhaustion of the soil is insured. Good husbandry, therefore, 
indicates either the application of a smaller dose at the recurrence of the 
wheat crop — or the occasional omission of lime altogether for an entire 
rotation. The practical farmer cannot have a better mode of ascertain- 
ing when his land is thus fully supplied with lime — than by making the 
trial upon alternate ridges, and marking the effect. 

6°. On poor arable lands, which are not naturally so, but which are 
worn out or exhausted by repeated liming and cropping, lime produces 
no good whateverf (Anderson, Brown, Morton). Such soils, if they do 
not already abound in lime, are, at least, equally destitute of numerous 
other kinds of food, organic and inorganic, by which health}'' plants are 
nourished, — and they are only to be restored to a fertile condition by a 

* " I never met," he says, " with a poor soil in its natural state, which was rot benefitted 
in a very great degree by calcareous matter when administered in proper quantities. But I 
liave met with several rich soils, which are fully impregnated with dung, on which lime ap- 
plied in any quantity produced not the smallest sensible effect." 

t "It is scarcely practicable to restore fertility to land, even of the best natural quality, which 
has been thus abused; and thin moorish soils, after being eihausted by lime, are not to be 
restored." (Brown). 



LIME DOES NOT BENEFIT EXHAUSTED SOILS. "395 

judicious admixture of all. This truth is confirmed by the practical ob- 
servation, that on soils so exhausted farm-yard manure along with the 
lime does not produce the same good results as in other cases. All 
that the soil requires is not supplied in sufficient abundance by these 
two substances laid on alone. 

7^. On lands of this kind, and on all in which vegetable matter is 
wanting, lime may even do harm to the immediate crop. It is apt to 
singe or burn the corn sown upon them (Brown) — an effect which is 
probably chemical, but which may in part be owing to its rendering 
more open and friable soils already by long arable culture too open al- 
ready (Morton). 

8°. A consideration of the circumstances above adverted to explains 
why, in some districts, and even in some whole provinces, the use of 
lime in any form should be condemned and even entirely given up. 
The soil has been impoverished through its unskilful application — or, 
by large admixtures of lime or marl for a series of years, the soil has 
been so changed as to yield no adequate return for new additions. Thus 
for a generation or two the practices of liming and marling are abandon- 
ed, to be slowly and reluctantly resumed again, when natural causes 
have removed the lime from the soil, and produced an accumulation of 
those other substances which, when associated with it, contribute to the 
productiveness of the land. 

§ 17. Effects of an overdose of lime. 

There are several effects which are familiar to the practical man as 
more or less observable when lime in any form is laid too lavishly upon 
the land. Thus 

1°. It is rendered so loose by an overdose as to be capable of holding 
no water (Karnes). Upon stiff clays a very large quantity indeed will 
be required to produce this effect. 

2°. By an overdose of quick-lime the land is hardened to such a de- 
gree as to be impervious to water or to the roots of plants. Several 
parts of the Carse of Gowrie are thus rendered so hard as to be unfit 
for vegetation (Kames).* This effect will be observed only in soils 
which are naturally wet and undrained, or where much rain has fallen 
and lingered on the land after the lime has been applied (p. 388). 

3°* But the most injurious effect of an over-liming, whether it be laid 
on at one or at successive periods, is the exhaustion by which it is suc- 
ceeded. "An overdose of slie'1-marl," says Lord Kames, "laid per- 
haps an inch thick, produces f)r a time large crops, but at last renders 
the soil capable of bearing neither corn nor grass, of which there are 
many examples in Scotland." The same is true of lime in any form. 
The increased fertility continues as long as there remains an adequate 
supply of organic (animal and vegetable) matter in the soil, but as that 
disappears the crops every year diminish both in quantity and in quality. 

An interesting illustration of this exhausting power of lime is afforded 
by the observed effects of long-continued marling upon certain poor soils 
in the province of Isere, in France. The marl there employed is a 
sandy marl, containing from 30 to 60 per cent, of carbonate of lime — 
very much like the lime-sand of Ireland or the shell-sand of the West- 

' Lord Karnes's Genlleman Farmer, edit. 1SC2. 



396 LEXGTH OF TIME DURING WHICH LIME ACTS. 

ern Islands already described (p. 371). A layer of this marl one-third 
of an inch thick, applied at intervals to a soil producing in its natural 
state only a three-fold return of rye every other year, causes it to yield 
for the first 10 or 12 years an eight-fold return of wheat. But after 40 
years' marling, the farmers now complain that the land will give only a 
four-fold return of wheat. But the cause of this reduction is to be found 
in the constant cropping with corn, in the growing of no green crops, 
and in the addition of no manure. Yet even with this treatment the 
land is still more productive than before the marling was commenced. 
It produces four returns instead of three, and it grows wheat where be- 
fore only rye would thrive and ripen. 

From the possession of this exhausting property has arisen the almost 
universally diffused proverb, that lime enriches the fathers but irnjwver- 
ishes the sons. The fault, however, is not in the lime, but in the improvi- 
dent fathers, who in this case, as in so many others, exhaust and incon- 
siderately squander the inheritance of their sons. If care be taken to 
keep up the supply of organic matter in the soil — by copious additions 
of manure or otherwise (p. 380) — lime may be added freely and a sys- 
tem of high farming kept up, by which both the present holder of the 
land and his successor will be equally benefitted. 

The opinion expressed by some of the highest authorities among 
practical men, that too much lime cannot be added, provided the soil 
abound sufficiently in vegetable matter, may perhaps be rather over- 
stated ; but it undoubtedly embodies the result of long-continued general 
observation — that the exhausting efTect of lime may be postponed indefi- 
nitely by a liberal managemeut of the land.* 

§ 18. Length of time during which lime acts. 

It is the fate of nearly all the superficial improvements of the soil, 
that they are only temporary in their duration. The action of lime 
ceases after a time, and the land returns to its original condition. The 
length of time which must elapse before this takes place will depend, 
among other circumstances, upon the quantity of lime added to, or orig- 
inally contained in, the soil — upon the kind of cropping to which it is 
subjected — on the nature of the soil itself — on the slope and exposure and 
natural moisture of the land, and on the climate in which it is situated. 

"We have seen that on the arable lands of the south of Scotland 20 
years is the longest period during which the doses there applied act 
beneficially upon the crops — while in other parts of the country re- 
newed applications are considered necessary at niuch shorter intervals. 
Mr. Dawson, of Frogden, who introduced the practice of liming into the 
Border counties of Scotland, observed that, when harrowed in with the 
grass seeds, its effect in improving the subsequent pasture was sensible 
for 30 years after. A heavy marling or chalking in the Southern and 
Midland counties of England is said also to last for 30 years.f and the 
same period is assigned to the sensible eflfect of the ordinary doses of 

• In Germany the necessary union of manure and marl is in the mouth of every peasant — 

Ohne mist 

1st das Geld fiir mergeln verq list. 

t Applied at a cost of 305. to 50s. per acre, according to the locality. — Mr. Pusey, Royal 
Agricultural Journal, iii., p. l>5. 



LIME NATURALLY SINKS INTO THE SOIL. 397 

lime-sand in Ireland, and of shell-sands and marls in several parts of 
France. 

The effect of the lime lessens gradually, and though at the end of an 
assignable number of years it becomes almost insensible, yet it does not 
altogether cease till a much later period. This period is in some cases 
so protracted that intelligent practical men are in many districts to be 
met with who believe — that certain grass lands would never forget a 
good dose of lime (p. 391, note). 

§ 19. Of the sinking of lime into the soil. 

One of the causes of this gradual diminution of the action of lime is to 
be found in the singular property it possesses of slowly sinking into the 
land, until it almost entirely disappears from the surface soil. It has 
been long familiar to practical men, that when grass lands, which have 
been limed on the sward, are after a time broken up, a white layer or 
band of lime is seen at a greater or less depth beneath the surface, but 
lodging, generally, where it has attained its greatest depth, between the 
upper, loose and fertile, and the lower, more or less impervious and un- 
productive soil. In arable lands the action of the plough counteracts 
this tendency in some measure, bringing up the lime again from be- 
neath, and keeping it mixed with the surface mould. Yet, through 
ploughed land it sinks at length, especially where the ploughing is shal- 
low, and even the industry of the gardener can scarcely prevent it from 
descending beyond the reach of his spade. 

The chief cause of this sinking is to be found in the extreme minute- 
ness of the particles into which slaked lime naturally falls. If a por- 
tion of slaked lime be mixed with water it forms a milky mixture, in 
which some lime is dissolved, but much more is held in suspension in 
an extremely divided state. When this milk is allowed to stand undis- 
turbed, the fine particles subside very slowly, and are easily again dis- 
turbed, but if thrown upon a filter they are arrested immediately, and 
the lime-water passes through clear. Suppose these fine particles to be 
mixed with the soil, and the rain to fall upon them, it will carry 
them downwards through the pores of the soil till the close subsoil acts 
the part of a filter, and arrests them. This tendency to be washed 
down is common not only to lime but to all minutely divided earthy 
matter of a sufficiently incoherent nature. Hence the formation of that 
more or less impervious layer of finely divided matter which so often 
forms the subsoil beneath free and open surface soils. And that lime 
should appear alone or chiefly to sink on any cultivated field, may arise 
from this circumstance — that the continued action of the rains had long 
before carried downwards the finer incoherent particles of other kinds 
which existed naturally in the soil, and therefore could find little else 
but the lime on which this action could be exercised. 

This explanation is satisfactory enough in the case of light and open 
soils, which are full of pores, but it appears less so in regard to stiff 
clays and to loamy soils, which are not only close and apparently void 
of pores, but seem themselves to consist of particles in a sufficiently 
minute state of division to admit of their being carried down by the 
rains in an equal degree with lime itself. This difficulty induced Lord 
Dundonald to suspect the agency of some chemical principle in produ- 



398 EFFKCTS OF SI^'KI^•G, AND REMEDIES FOR IT. 

cing the above eflect.* As the lime, however, is unchanged after it has 
descended, is still in a powdery state, and exhibits no appearance of 
havino; been dissolved, it is difficult to imagine any chemical action by 
which such a siiiking could have been brought about. 

It is possible that in grass lands the earth-worms, which contribute so 
much to the gradual production of a fine mould, may, by bringing up 
the other earthy matters only, contribute to the apparent sinking of the 
lime, as well as of certain other io})-dressings.f 

The effects of this sinking are to remove the lime from the surface 
soil, and to form a layer of calcareous matter which in wet or imper- 
vious bcttoms will harden and form a more or less solid bed or j^aw, 
through which the rains and roots refuse to penetrate, and which the 
subsoil plough in some districts can tear up with difficulty. On our 
stiffer soils it encourages the growth of the troublesome coltsfoot, and in 
the open ditches of the wholesome water-cress. 

The practical remedies for this sinking are of two kinds : 

1°. The ploughing of a deeper furrow, and hence one of the benefits 
which in many localities follow the use of the trench plough (p. 322). 

2°. The sowing of deep-rooted and lime-loving crops, such as lucerne 
and sainfoin, which in such soils not only thrive, but bring up in their 
stems, and restore to the surface, a portion of the lime which had pre- 
viously descended, and thus make it available to the after-crops. 

§ 20. Why liming wust he repeated. 

Lime which sinks, as above described, does not v/holly escape from 
the soil, but may by judicious management be again brought to the 
surface. Such a sinking, therefore, does not necessarily call for the ad- 
dition of a fresh dose of lime, nor does it explain the reason why in prac- 
tice the application of lime to the land must at certain intervals be every 
where repeated. 

We have already seen that the influence of the lime we have laid 
upon our fields after a time gradually diminishes — the grass becomes 
sensibly less rich year by year, the crops of corn less abundant, the kind 
of srain it will ripen less valuable. Does the lime, you might ask, ac- 
tually disappear from the soil, or does it merely cease to act ? This 
question has been most distinctly answered by an experiment of Lam- 
padius. He mingled lime with the soil of a piece of ground till it was 
in the proportion of 1-19 per cent, of the whole, and he determined sub- 
sequently, by analysis, the quantity of lime it contained in each of the 
three succeeding years. 

The first year it contained . 1-19 per cent, carbonate of lime. 

The second year .... 0-89 

The third year 0-52 •* 

The fourth year .... 0-24 " " } 

There can be no question, therefore, that the lime gradually disappears 
or is removed from the soil. 

* "In clayey and loamy soils, which areC) equally diffusible with lime, and nearly of the 
same specific gravity, the tendency which lime has to sink cannot be accounted for simply 
on meclianical principles."— Lord DundonaUl's Agricultural Chemistry, p. 45. 

t See in a subsequent lecture the remarks on laying dozen to grass; also the Author's Ele- 
ments of Agricultural Chemistry, p. 212. 

t Schiibler, Agricultural Chemie, ii., p. 141. 



WHY LIMING MUST BE REPEATED. 399 

The agencies by which this removal is effected are of several kinds. 
1°. In some cases it sinks, as we have already seen, and escapes into 
the subsoil beyond the reach of the plough or of the roots of our culti- 
vated crops. 

2°. A considerable quantity of lime is annually removed from the 
soil by the crops which are reaped from it. We have already seen 
(Lee. X., § 4,) that in a four \'ears' rotation of alternate green and corn 
crops the quantity of linie contained in the average produce of good 
land amounts to 248 lbs. This is equal to 60 lbs. of quick-lime or 
107 lbs. of carbonate of lime every year. The whole of this, however, 
is not usually lost to the land. Part at least is restored to it in the ma- 
nure into v/hich a large proportion of the produce is usually converted. 
Yet a considerable quantity is always lost — escaping chiefly in the 
liquid manure and in the drainings of the dung-heaps — and this loss 
must be repaired by the renewed addition of lime to the land. 

3°. But the rains and natural springs of water percolating through the 
soil remove, in general, a still greater proportion. While in the quick 
or caustic state, lime is soluble in pure water- Seven hundred and fifty 
pounds of water will dissolve about one pound of lime. The rains that 
fall, therefore, cannot fail, as they sink through the soil, to dissolve and 
carry away a portion of the lime so long as it remains in the caustic state- 
Again, quick-lime, when mixed with the soil, speedily attracts car- 
bonic acid, and becomes, after a time, converted into carbonate, which 
is nearly insoluble in pure water- But this carbonate, as we have 
already seen (Lee. IIL, § 1), is soluble in water impregnated with car- 
bonic acid — and as the drops of rain in falling absorb this acid from the 
air, they become capable, when they reach the soil, of dissolving an 
appreciable quantity of the finely divided carbonate which they meet 
with upon our cultivated lands. Hence the water that flows from 
the drains upon such lands is always impregnated with lime, and 
sometimes to so great a degree as to form calcareous deposits in the inte- 
rior of the drains themselves, where the fall is so gentle as to allow the 
waterto linger a sufficient length of time in the soil. 

It is impossible to estimate the quantity of lime which this dissolving 
action of the rains must gradually remove. It will vary with the amount 
of rain which falls in each locality, and with the slope or inclination of 
the land ; but the cause is at once universal and constantly operating, 
and would alone, therefore, render necessary, after the lapse of years, the 
application of new doses of lime both to our pastures and to our arable 
fields. 

4°. During the decay of vegetable matter, and the decomposition of 
mineral compounds, which take place in the soil where lime is present, 
new combinations are formed in variable quantities which are more solu- 
ble than the carbonate, and which therefore hasten and facilitate this 
washing out of the lime by the action of the rains. Thus chloride of 
calcium, nitrate of lime, and gypsum, are all produced — of which the 
two former are eminently soluble in water — while organic acids also re- 
sult from the decay of the organic matter, with some of which the lime 
forms readily soluble compounds (salts) easily removed by water. 

The ultimate resolution of all vegetable matter in the soil into carbonic 
acid and water (Lee. VIII., § 3,) likewise aids the removal of thelirae. 
34 



400 ACTION OF LIME UPON THE SOIL, AND AS THE FOOD OF PLANTS. 

For if the soil be every where impregnated with carbonic acid, the 
^•ain and spring waters that flow through it will also become charged 
Twith this gas, and thus be enabled to dissolve a larger portion of the 
Carbonate of lime than they could otherwise do. Thus theory indi- 
cates, what I believe experience confirms, that a given quantity of lime 
will disappear the sooner from afield, the more abundant the animal and 
vegetable matter it contains. 

§ 21. Theory of the action of lime. 

Lime acts in two ways upon the soil. It produces a mechanical alte- 
ration which is simple and easily understood, and is the cause of a 
series of chemical changes, which are really obscure, and are as yet 
susceptible of only partial explanation. 

In tlie finely divided state of quick-lime, of slaked lime, or of soft 
and crumbling chalk, it stiffens very loose soils, and opens the stiffer 
clays, — while in the form of limestone gravel or of shell sand, it may 
be employed either for opening a clay soil or for giving body and firm- 
ness to boggy land. These effects, and their explanation, are so obvious 
to you, that it is unnecessary to dwell upon them. 

The purposes served by lime as a chemical constituent of the soil are 
at least of four distinct kinds. 

1°. It supplies a kind of inorganic food which appears to be necessary 
to the healthy growth of all our cultivated plants. 

2°. It neutralizes acid substances which are naturally formed in the 
soil, and decomposes or renders harmless other noxious compounds which 
are not unfrequenlly within reach of the roots of plants. 

3°. It changes the inert vegetable matter in the soil, so as gradually 
to render it useful to vegetation. 

4°. It causes, facilitates, or enables other useful compounds, both or- 
ganic and inorganic, to be produced in the soil,— or so promotes the de- 
composition of existing compounds as to prepare them more speedily 
for entering into the circulation of plants. 

These several modes of action it will be necessary to illustrate in 
some detail, 

§ 22. Of lime as the food of plants. 

In considering the chemical nature of the ash of plants (Lee. X., § 3 
and 4), we have seen that lime in all cases forms a considerable pro- 
portion of its whole weight. Hence the reason why lime is regarded as 
a necessary food of plants, and hence also one cause of its beneficial in- 
fluence in general agricultural practice. 

The quantity of pure lime contained in the crops produced upon one 
acre during a four years' rotation amounts, on an average, to 242 lbs. 
which are equal to about 430 lbs. (say 4 cwt.) of carbonate of lime, in 
the state of marl, shell-sand, or lime-stone gravel. (See Lee. X., § 3.) 
It is obvious, therefore, that one of the most intelligible purposes served 
by lime, as a chemical constituent of the soil, is to supply this compara- 
tively large quantity of lime, which in some form or other must enter 
into the roots of plants. 

But the different crops which we grow contain lime in unlike propor- 



ACTS CHIEFLY UPON THE ORGANIC MATTER OF THE SOIL. 401 

lions. Thus the average produce of an acre of land under the follow- 
ing crops contains of lime — 

Grain or roots. Straw or tops. Total. 

Wheat, 25 bushels, ... 1-5 72 8-7 lbs. 

Barley, 38 bushels, ... 2-1 129 15 lbs. 

Oats, 50 bushels, .... 2-5 5-7 8-2 lbs. 

Turnips, 25 tons, . . . 458 930 138-8 lbs. 

Potatoes, 9 tons, . ... 66 2594 2660 lbs. 

Red clover, 2 tons, ... — 1260 1260 lbs. 

Rye grass, 2 tons, ... — 330 330 lbs. 

These quantities are not constant, and wheat especially contains much 
more lime than is above stated, when it is grown upon land to which 
lime has been copiously applied. But the very different quantities con- 
tained in the several crops, as above exhibited, shew that one reason why 
lime favours the growth of some crops more than others is, that some actu- 
ally take up a larger quantity of lime as food. These crops, therefore, 
require the presence of lime in greater proportion in the soil, in order 
that they may be able to obtain it so readily that no delay may occur in 
the performance of those functions or in the growth of those parts to which 
lime is indispensable. 

§ 23. The chemical action of lime is exerted chiefly upon the organic 

matter of the soil. 

There are four circumstances of great practical importance in regard 
to the action of lime, which cannot be too carefully considered in refe- 
rence also to the theory of its operation. These are — 

1°. That lime has little or no effect upon soils in which organic mat- 
ter is deficient. 

2°. That its apparent effect is inconsiderable during the first year 
after its application, compared with that which it produces in the second 
and third years. 

3°. That its effect is most sensible when it is kept near the surface of 
the soil, and gradually becomes less as it sinks towards the subsoil. 
And, 

4°. That under the influence of lime the organic matter of the soil 
disappears more rapidly than it otherwise would do, and that after it 
has thus disappeared fresh additions of lime produce no further good 
effect. 

It is obvious from these facts, that in general the main beneficial pur- 
pose served by lime is to be sought for in the nature of its chemical ac- 
tion upon the organic matter of the soil — an action which takes place 
slowly, which is hastened by the access of air, and which causes the 
organic matter itself ultimately to disappear. 

§ 24. Of the forms in which organic matter usually exists in the soiU and 
the circumstances under which its decomposition may taJce place. 

I. — The organic matter which lime thus causes to disappear is pre- 
sented to it in one or other of five different forms : 

1°. In that of recent, often green, moist, and undecomposed roots, 
leaves, and stems of plants. ' 



402 UPON THE DECOMPOSITIOrJ OF ORGANIC 31ATTER. 

2°. Ill that of dry, and still undecomposed, vegetable matter, such 
as straw. 

3°. In a more or less decayed or decaying state, generally black or 
brown in colour — and often in some degree soluble in water. 

4°. In what is called the inert state, when spontaneous decay ceases 
to be sensibly observed. And 

5°. In the stale of chemical combination with the earthy substances 
— with the alumina for example, and with the lime or magnesia — al- 
ready existing in the soil. 

Upon these several varieties of organic matter lime acts with differ- 
ent degrees of rapidity. 

II. — The final result of the decomposition of these several forms of 
organic matter, when they contain no nitrogen, is their conversion into 
carbonic acid and water only (Lee. VIII., § 3). They pass, however, 
through several intermediate stages before they reach this point — the 
number and rapidity of which, and the kind of changes they undergo 
at each stage, depend upon the circumstances under which the decom- 
position is effected. Thus the substance may decompose — 

1°. Alone, in which case the changes that occur proceed slowly, and 
arise solely from a new arrangement of its own particles. This kind of 
decomposition rarely occurs to any extent in the soil. 

2°. In the presence of water only. — This also seldom takes place in 
the soil. Trees long buried in moist clays impervious to air, exhibit the 
kind of slow alteration which results from the presence of water alone. 
In the bottoms of lakes, ditches, and boggy places also, from which in- 
flammable gases arise, water is the principal cause of the more rapid 
decomposition. 

3°. In the presence of air only. — In nature organic matter is never 
placed in this condition, the air of our atmosphere being always largely 
mixed with moisture. In dry air decomposition is exceedingly slow, 
and the changes which dry organic substances undergo in it are often 
scarcely perceptible. 

4°. In the presence of both water and air. — This is the almost uni- 
versal condition of the organic matter in our fields and farm-yards. The 
joint action of air and water, and the tendency of the elements of the or- 
ganic matter to enter into new combinations, cause new chemical 
changes to succeed each other with much rapidity. It will of course 
be understood that moderate warmth is necessary to the production of 
these effects.* 

5°. In the presence of lime, or of some other alkaline substance (pot- 
ash, soda, or magnesia). — Organic matter is often found in the soil in 
such a state that the conjoined action of both air and water are unable 
to hasten on its decomposition. A new chemical agency must then be 

* A familiar illustration of the conjoined eflBcacy of airand water in producing oxidation is 
exhibited in their action upon iron. If a piece of polished iron be kept in perfectly dry air 
it will not rust. Or if it be completely covered over with pure water in a well- stoppered 
bottle, from which air is excluded, it will remain bright and untarnished. But if a polished 
rod of iron be put into an open vessel half full of water, so that one part of ilslengih only is 
under water — then the rod will begin very soon to rust at the surface of the water, and a 
brown ochrey ring of oxide will form around it, exactly where the air and water meet. 
From this point the rust will gradually spread upwards and downwards. So it is with the 
organic matter of the soil. Wherever the air and water meet, their decomposing action 
upon it, in ordinary temperatures, soon becomes perceptible. 



INFLUENCK OF ALKALINE SUBSTANCES. 403 

introduced, by which the elements of the organic matter may again be 
set in motion. Lime is the agent which for this purpose is most largely 
employed in practical agriculture. 

§ 25. General action of alkaline substances upon organic matter. 

It is this action of alkaline matters upon the organic substances of the 
soil in the presence of air and water that we are principally to investigate. 

When organic matter undergoes decay in the presence of air and 
water only, it first rots, as it is called, and blackens, giving off water or 
its elements chiefly, and forming humus — a mixture of humic, ulmic, 
and some other acids (Lee. XIII., § 1,) with decaying vegetable fibre. 
It then commences, at the expense of the oxygen of the air and of water, 
to form other more soluble acids (malic, acetic, lactic, crenic, mudesic, 
&.C.), among which is a portion of carbonic — and, by the aid of the hy- 
drogen of the water which it decomposes, one or more of the many 
compounds of carbon and hydrogen, which often rise up, as the marsh- 
gas does, and escape into the air (Lee. VIII., § 3). 

Thus there is a tendency towards the accumulation of acid substances 
of vegetable origin in the soil, and this is more especially the case when 
the soil is moist, and where much vegetable matter abounds. The effect 
of this super-abundance of acid matter is, on the one hand, to arrest the 
further natural decay of the organic matter, and, on the other, to render 
the soil unfavourable to the healthy growth of young or tender plants. 

The general effect of the presence of alkaline substances in the soil 
is to counteract these two evils. They combine with and thus remove 
the sourness of the acid bodies as they are formed. In consequence of 
this the soil becomes sweeter or more propitious to vegetation, while the 
natural tendency of the vegetable matter to decay is no longer arrested. 

It is thus clear that an immediate good effect upon the land must fol- 
low either from the artificial application or from the natural presence of 
alkaline matter in the soil — while at the same time it will cause the 
vegetable matter to disappear more rapidly than would otherwise be the 
case. But the effect of such substances does not end here. They actu- 
ally dispose or provoke — pre-dispose, chemists call it — the vegetable 
matter to continue forming acid substances, in order that they may com-^ 
bine with them, and thus cause the organic matters to disappear more 
rapidly than they otherwise would do — in other words, they hasten for-^ 
ward the exhaustion of the vegetable matter of the soil. 

Such is the general action oi^ all alkaline substances. This action 
they exhibit even in close vessels. Thus a solution of grape sugar, mixed 
with potash, and left in a warm place, slowly forms ^^ie/asszc acid — while 
in cold lime-water the same sugar is gradually converted into another 
acid called the glucic. But in the air other acids are formed in the same 
mixtures, and the changes proceed more rapidly. Such is the case also 
in the soil, where the elements of the air and of water are generally at 
hand to favour the decomposition. 

But the nature of the alkaline matter which is present determines 

also the rapidity with which such changes are produced. The most 

powerful alkaline substances — potash and soda — produce all the above 

effects most quickly ; lime and magnesia are next in order; and the alu* 

34* 



404 ACTION OF CAUSTIC ilME DPOiN ORGAMC MATTtR 

mina of the clay soils, though much inferior to all of these, is far from 
being without an important influence. 

Hence one of the benefits which result from the use of wood-ashes 
containing carbonate of potash, when employed in small quantities, and 
along with vegetable and animal njanures, as they are in this country; 
but hence also the evil effects which are found to follow from the appli- 
cation of them in too large doses. Thus in countries where wood 
abounds, and where it is usual, as in Sweden and Northern Russia, 
to burn the forests and to lay on their ashes as manure, the tillage can 
be continued for a few years only. After one or two crops the land is 
exhausted, and must again be left to its natural produce. 

§ 26. Special effects of caustic lime upon the several varieties of 
organic matter in the soil. 

The effects of lime upon organic matter are precisely the same in 
kind as those of the alkalies in general. They are only less in degree, 
or take place more slowly, than when soda or potash is employed. 
Hence, the greater adaptation of lime to the purposes of practical agri- 
culture. 

1°. Action of caustic lime alone upon vegetable matter. — If the fresh 
leaves and twigs of plants, or blades and roots of grass, be introduced 
into a bottle, surrounded with slaked lime, and corked, they will slow- 
ly undergo a certain change of colour, but they may be preserved, it is 
said, for years, without exhibiting any striking change of texture (Mr. 
Garden). If dry straw be so mixed with slaked lime, it will exhibit 
still less alteration. In either case also the changes will be even less 
perceptible, if, instead of hydrate of lime, the carbonate (or mild lime), 
in any of its forms, be mixed with these varieties of vegetable matter. 
On some other varieties of vegetable matter, — such, for example, as are 
undergoing rapid decay, or have already reached an advanced stage of 
decomposition, — an admixture of slaked lime pioduces certain percepti- 
ble changes immediately, and mild lime more slowly, but these changes 
being completed, the tendency of lime alone is to arrest rather than to 
promote further rapid alterations. Hence, the following opinions of 
experienced practical observers must be admitted to be theoretically 
correct — in so far as they refer to the action of lime alone. 

" If straw of long dung be mixed with slaked lime it will be pre- 
served" (Morton).* 

" Lime mixed in a mass of earth containing the live roots and seeds 
of plants will not destroy them" (Morton). 

" Sir H. Davy's theory, that lime dissolves vegetable matter, is given 
up ; in fact, it hardens vegetable matter" (Mr. Pusey).f 

These opinions, I have said, are probably correct in so far as regards 
the unaided action of lime. They even express, with an approach to 
accuracy, what will take place in the interior of compost heaps of a 
certain kind, or in some dry soils ; but that they cannot apply to the ordi- 
nary action of lime upon the soil is proved by the other result of universal 
observation, that lime, so far from preserving the organic matter of the 

• On Soils, 3rd edition, p. 181. 

t Royal AgriculturcUJournal, iil., p. 212. 



IN THE PRESENCE OF AIU A>'D WATER. 405 

land to which it is applied, in reality wastes it — causes, that is, or dis- 
poses it to disappear. 

2°. Action of caustic lime on organic matter in the presence of air arid 
water. — In the presence of air and water, when assisted by a favouring 
temperature, vegetable matter, as we have already seen, undergoes 
spontaneous decomposition. In the same circumstances lime promotes 
and sensibly hastens this decomposition, — altering the forms or stages 
through which the organic matter must pass — but bringing about more 
speedily the final conversion into carbonic acid and water. During its 
natural decay in a moist and open soil, organic matter gives off a por- 
tion of carbonic acid gas which escapes, and forms certain other acids 
which remain in the dark mould of the soil itself. When quick or 
slaked lime is added to the land, its first effect is to combine with these 
acids — to form carbonate, humate, &c., of lime — till the whole of the 
acid matter existing at the time is taken up. That portion of the lime 
which remains uncombined, either slowly absorbs carbonic acid from 
the air or unites with the carbonate already formed, to produce the 
known compound of hydrate with carbonate of lime* — waiting in this 
state in the soil till some fresh portions of acid matter are formed with 
which it may combine. But it does not inactively wait; it persuades 
and influences the organic matter to combine with the oxygen of the air 
and water with which it is surrounded, for the production of such acid 
substances — till finally the whole of the lime becomes combined either 
with carbonic or with some other acid of organic origin. 

Nor at this stage are the action and influence of lime observed to 
cease. On the contrary, this result will, in most soils, be arrived at in 
the course of one or two years, while the beneficial action of the lime 
itself may be perceptible for 20 or 30 years. Hence there is much ap- 
parent ground for the opinion of Lord Kames, " that lime is as effica- 
cious in its (so called) effete as in its caustic state." Even the more 
strongly expressed opinion of the same acute observer, " that lime pro- 
duces little effect upon vegetables till it becomes effete" — derives much 
support from experience — since lime is known to have comparatively 
little effect upon the productiveness of the land till one or two years 
after its application; and this period, as I have said, is in most localities 
sufficient to deprive even slaked lime of all its caustic properties. 

Of the saline compoundsf which caustic lime thus forms, either im- 
mediately or ultimately, some, like the carbonate and humate, being 
very sparingly soluble in water, remain more or less permanently in the 
soil ; others, like the acetate of lime, being readily soluble, are either 
washed out by the rains or are sucked up by the roots of the growing 
plants. In the former case they cause the removal of both organic 
matter and of lime from the land ; in the latter they supply the plant 
with a portion of organic food, and at the same time with lime — with- 
out which, as we have frequently before remarked, plants cannot be 
maintained in their most healthy condition. 

* That compound, namely, which is produced when quicklime slakes spontaneously in 
the air. — See jiage 368. 

t Saline compounds or salts are always formed when lime, magnesia, potash, soda, &c., 
Comhini? with nci-is. 



406 ACTIOJN or CARBONATE OF LIME UPON VEGETABLE MATTER. 

§ 27. Action of mild {or carbonate of) lime upon the vegetable matter 

of the soil. 

The main utility of lime, therefore, depends upon its prolonged after- 
action upon the vegetable matter of the soil. What is this action, and 
in what consist the benefits to which it gives rise? 

In answering this question, it is of importance to observe that all the 
effects produced by alkaline matter in general — whether by lime or by 
potash — in the caustic state, are produced in kind also by the same sub- 
stances in the state of carbonate. The carbonic acid with which they 
are united is retained by a comparatively feeble affinity, and is dis- 
placed with greater or less ease by almost every other acid compound 
which is produced in the soil. With this displacement is connected an 
interesting series of beautiful reactions, which it is of consequence to 
understand. 

You will recollect that the great end which nature, so to speak, has 
in view, in all the changes to which she subjects organic matter in the 
soil, is to convert it — with the exception of its nitrogen — into carbonic 
acid and water. For this purpose it combines, at one time, with the 
oxygen of the air, while at another it decomposes water and unites with 
the oxygen or the hydrogen which are liberated, or with both to form 
new chemical combinations. Each of these new combinations is either 
immediately preliminary to or is attended by the conversion of a por- 
tion of the elements of the organic matter into one or other of those 
simpler forms of matter on which plants live. Now during these pre- 
liminary or preparatory steps, acid substances, as I have already ex- 
plained, are among others constantly produced. With these acids, the 
carbonate of lime, when present in the soil, is ever ready to combine. 
But in so combining, it gives off' the carbonic acid with which it is al- 
ready united, and thus a continual, slow evolution of carbonic acid is 
kept up as long as any undecomposed carbonate remains in the soil. 

I do not attempt to specify by name the various acid substances which 
are thus formed during the oxidation of the organic matter, and which 
successively unite wilh the lime, because the entire series of interesting 
and highly important changes, which organic substances undergo in the 
soil, has as yet been too little investigated, to permit us to do more than 
speak in general terms of the nature of the chemical compounds which 
are most abundantly produced. Of two facts, however, in regard lo 
them, we are certain — that they are simpler in their constitution than 
the original organic matter itself, from which they are derived — and that 
they have a tendency to assume still simpler forms, if they continue to 
be exposed to the same united action of air, water, and alkaline sub- 
stances. 

Hence the compounds which lime has formed with the acid substances 
of the soil, themselves hasten f()rward to new decompositions, — unite 
with more oxygen, liberate slowly portion after portion of their carbon 
in the form of carbonic acid, and of their hydrogen in the form of water, 
till at length the lime itself is left again in the stale of carbonate, or in 
union with carbonic acid only. This residual carbonate begins again 
the same round of changes through which it had previously passed. It 
gives up its carbonic acid at the bidding of some more powerful organic 
acid produced in its neighbourhood, while this acid, by exposure to the 



SUMMARY OF THE CHANGES PRODUCED BY LIME. 407 

due influences, undergoes new alterations till it also is finally resolved 
into carbonic acid and water. 

Two circumstances are deserving to be borne in mind in reference to 
these successive decompositions— ^rs/, that in the course of them more 
soluble compounds of lime are now and then formed, some of which are 
washed out by the rains, and escape from the soil, while others minister 
to the growth of plants ; — and second, that very much carbonic acid is 
produced as their final result — of which also part is taken up by the 
roots of plants, and part escapes into the air. Thus at every successive 
stage a portion of organic matter is lost to the soil. If this quantity be 
greater than that which is yearly gained in the form of roots or decayed 
leaves and stems of plants, or of manure artificially added, the soil will 
be gradually exhausted — if less, it will every year become more rich in 
vegetable matter. 

It is also to be borne in mind, that although, for the purpose of illus- 
tration, I have supposed the carbonate of lime first formed in the soil to 
be subsequently combined with other acids, which gradually decompose 
and leave it again in the state of carbonate, — yet it will rarely happen 
that the whole of the carbonate of lime in the soil will be in any of these 
new states of combination. In general a part of it only is thus at any 
one time employed in working up the acid substances produced. But it 
is necessary that it should be universally diffused through the soil in order 
that it may be every where at hand to perform the important part of its 
functions above explained. It is only where little lime is present, or 
where decaying vegetable matter is in exceeding abundance, that the 
whole of the carbonate can at one and the same time disappear (p. 380). 



The changes, therefore, which lime and organic matter, supposed to 
be free from nitrogen, respectively undergo, and their mutual action in 
the soil, may be summed up as follows : — 

1°. The organic matter, under the influence of air and moisture, 
spontaneously decomposes, and besides carbonic acid which escapes, 
forms also other acid substances which linger in the soil. 

2°. With these acids the quick-lime combines, and, either by Its union 
with them or with carbonic acid from the air, soon (comparatively) loses 
its caustic state. 

3°. The production of acid substances by the oxidation of the organic 
matter — goes on more rapidly under the disposing influence of the lime, 
whether caustic or carbonated. These acids combine with the lime, 
liberating from it, when in the state of carbonate, a slow but constant 
current of carbonic acid, upon which plants at least partly live. 

4°. The organic acid matter which thus unites with the lime continues 
itself to be acted upon by the air and water, aided by heat and light — it- 
self passes through a succession of stages of decomposition, at each of 
which it gives off water or carbonic acid, retaining still its hold of the lime, 
till at last being wholly decomposed it leaves the lime again in the state 
of carbonate, ready to begin anew the same round of change. 

During this series of progressive decompositions, certain more soluble 
compounds of lime are formed, by which plants are in part at least sup- 



408 COMPARATIVE UTILITY OF BURNED AND UNBURNED LIME. 

plied with this earth, and which with the aid of the rains carry off both 
lime and organic matter from the soil. 

And, again, the more rapid the production of the acid substances 
which result from the union of the organic matter with oxygen, the 
more abundant in general also the production of those gaseous and vola- 
tile compounds which they form by uniting with hydrogen, so that, in 
promoting the formation of the one class of bodies lime also favours the 
evolution of the other in greater abundance, and thus in a double measure 
contributes to the exhaustion of the soil. 

The disposing action of lime to this twin form of decomposition, few 
varieties of organic matter can resist, — and hence arises the well known 
efficacy of lime in resolving and rendering useful the apparently in- 
ert vegetable substances that not unfrequently exist in the soil. 

§ 28. Of the comparative utility of burned and unhurned lime. 

Is there no advantage, then, you may ask, in using caustic or burned 
rather than carbonated or unburned lime? If the ultimate effects of 
both upon the land be the same, why be at the expense of burning ? 
Among other benefits may be enumerated the following : — 

1°. By burning and slaking, the lime is reduced to the state of an im- 
palpable powder, finer than could be obtained by any available method 
of crushing. It can in consequence be diffused more uniformly through 
the soil, and hence a smaller quantity will produce an equal effect. 
This minute state of division also promotes in a wonderful degree the 
chemical action of the lime. In all cases chemical action takes place 
between exceedingly minute particles of matter, and among solid sub- 
stances the more rapidly, the finer the powder to which they can be re- 
duced. Thus a mass of iron or lead slowly rusts or tarnishes in the air, 
but if the mass of either metal be reduced to the stale of an impalpable 
powder — which can be done by certain chemical means — it will take 
fire when simply exposed to the air at the ordinary temperature, and 
will burn till it is entirely converted into oxide. By mere mechanical 
division the apparent action of the oxygen of the air upon metals is aug- 
mented and hastened in this extraordinary degree — and a similar result 
follows when lime in an impalpable state is brought into contact with 
the vegetable matter upon which it is intended to act. 

2°. The effect of burned lime is more powerful and more immediate than 
that of unburned lime in the form of chalk, marl, or shell sand. Hence 
it sooner neutralizes the acids which exist in the soil, and sooner causes 
the decomposition of vegetable matter of every kind to commence, upon 
which its efficacy, in a greater degree, depends. Hence, when it can ea- 
sily be procured, it is better fitted for sour grass or arable lands, for such as 
contain an excess of vegetable matter, and especially for such as abound 
in that dead or inert form of organic matter which requires a stronger 
stimulus — the presence of more powerful chemical affinites, that is — to 
bring it into active decomposition. In such cases, the lime has already 
done much good before it has been brought into the mild state — and re- 
maining afterwards in this state in the soil, it still serves, in a great 
measure, the same slower after-purposes as the original addition of car- 
bonate would have done. 

3°. Besides, if any portion of it, after the lapse of two or three years, 



ORGANIC MATTKK OF THE SOIL CONTAINS NITROGEN. 409 

Still linger in the caustic state (p. 368), it will continue to provoke more 
rapid changes among the organic substances in the soil, than mild lime 
alone could have done. 

4''. Further, quick-Hme is soluble in water, and hence every shower 
that falls and sinks into the soil carries with it a portion of lime, so long 
as any of it remains in the caustic state. It thus reaches acid matters 
that lie beneath the surface, and alters and ameliorates even the subsoil 
itself. 

5^. It is not a small additional recommendation of quick-lime, that by 
burning it loses about 44 percent, of its weight, thus enabling nearly 
twice the quaniity to be conveyed from place to place at the same cost 
of transport. Tliis not only causes a direct saving of money, — as when 
the burned chalk of Antrim is carried by sea to the Ayrshire coasts — 
but an additional saving of labour also upon the farm, — where the num- 
ber of hands and horses is often barely sufficient for the necessary work. 

§ 29. Action of lime on organic substances which contain nitrogen. 

I have hitherto, for the sake of simplicity, directed your attention 
solely to the action, whether immediate or remote, which is exercised 
by lime upon organic matter supposed to contain no nitrogen. Its action 
upon compounds in which nitrogen exists is no less beautiful and simple, 
perhaps even more intelligible and more obviously useful to vegetation. 

There are several well known facts which it is here of importance for 
us to consider — 

1°. That the black vegetable malter of the soil always contains ni- 
trogen. Even that which is most inert retains a sensible proportion of 
it. It exists in dry peat to the amount of about 2 per cent, of its weight, 
and still clings to the other elements of the organic matter, even after it 
has undergone those prolonged changes by which it is finally converted 
into coal. Since nitrogen, therefore, is so important an element in all 
vegetable food, and so necessary in some form or other to the healthy 
growth and maturity of plants, it must be of consequence to awaken 
this element of decaying vegetable matter, when it is lying dormant, 
and to cause it to assume a form in which it can enter into and become 
useful to our cultivated plants. 

2°. That if vegetable matter of any kind be heated with slaked lime, 
the whole of the nitrogen it may contain, in whatever state of combina- 
tion it may previously exist, will be given off in the form of ammonia. 
The same takes place still more easily if a quantify of hydrate of potash 
or of hydrate of soda be mixed with the hydrate of lime. Though it 
has not as yet been proved by direct experiment — yet I consider it to be 
exceedingly probable, that what takes place quickly in our laboratories, 
at a coiijparatively high temperature, may take place more slowly also 
in the soil, and at the ordinary temperature of the atmosphere. 

3°. That when animal and vegetable substances are mixed with 
earth, lime, and other alkaline matters, in the so-called nitre beds (Lee. 
VIII., § 5), ammonia and nitric acid are both produced, the quantity of 
nitrogen contained in the weight of these compounds extracted being 
much greate^r than was originally present in the animal and vegetable 
matter employed (Dumas). Under the influence of alkaline substances, 
therefore, even when not in a caustic state, the decay of animal and ve- 



410 ANALOGOUS DECOMPOSITIOIV OF ALL ORGANIC SUBSTANCES. 

getable matter in the presence of air and moisture causes some of the 
nitrogen of the atmosphere to become fixed in the soil in the form of am- 
monia or of nitric acid. What takes place on the confined area of a 
nitre bed, may take place to some extent also in the wider area of a well- 
limed and well-manured field. 

In the action of alkalies in the nitre bed, disposing to the production 
of nitric acid, we observe the same kind of agency, which we have al- 
ready attributed to lime, in regard to the more abundant elements which 
exist in the vegetable matter of the soil. It gently persuades all the 
elements — nitrogen and carbon alike — to unite with the oxygen of air 
and water, and thus ultimately to form acid compounds with which it 
may itself combine. 

The action of lime upon such organic matters containing nitrogen as 
usually exist in the soil, may, therefore, be briefly stated as follows:— 

1°. These substances, like all other organic matter, undergo in moist 
air — and, therefore, in the soil — a spontaneous decomposition, the gen- 
eral result of which is the production of ammonia, and of an acid sub- 
stance with which the ammonia may combine. This change is pre- 
cisely analogous to that which takes place in such substances as starch 
and woody fibre, which contain no nitrogen. In each case, one portion 
of the elements unites with oxygen to produce an acid, the other with 
hydrogen to form a compound possessed of alkaline or indifferent pro- 
perties. Thus, — 

With oxygen. With hydrogen. 

^^ . , , . . J ( Carbonic, ulmic, and { Marsh ffas or other 

Vegetable matter produces. .| other acids. J carburetted hydrogens. 

Animal matter produces . • | ^^^dTthTacids^^^^ 

If the ammonia happen to be produced in larger relative quantity 
than the acids with which it is to combine, or if the carbonic be the 
only acid with which it unites, a portion of it may escape into the 
air. This rarely happens, however, in the soil, the absorbent proper- 
ties of the earthy matters of which it consists being in most cases suffi- 
cient to retain the ammonia, till it can be made available to the pur- 
poses of vegetable life. 

When caustic (hydrate of) lime is added to a soil in which ammonia 
exists in this state of combination with acid matter, it seizes upon the 
acid and sets the ammonia free. This it does with comparative slow- 
ness, however — for it does not at once come in contact with it all — and 
by degrees, so as to store it up in the pores of the soil till the roots of 
plants can reach it, or till it can itself undergo a further change by 
which its nitrogen may be rendered more fixed (p. 411). 

Carbonate of lime, on the other hand, still more slowly persuades the 
ammonia to leave the acid substances (ulmic, nitric? &c.), with which 
it is combined, and yielding to it in return its own carbonic acid, ena- 
bles it in the state of soluble carbonate of ammonia to become more im- 
mediately useful to vegetation. 

2°. But in undergoing this spontaneous decay, even substances con- 
taining nitrogen reach at length a point at which decomposition appears 
to stop — an inert condition in which, though nitrogen be present as in 
peat, they cease sensibly to give it off in such a form or quantity as to 



AMMONIA AND NITRIC ACID FORMED. 411 

be capable of ministering to vegetable growth. Here caustic lime steps 
in more quickly, and mild lime by slower degrees, to promote the fur- 
ther decay. It induces the carbonaceous matter to take oxygen from 
the air and from water and to form acids, and the nitrogen to unite with 
the hydrogen of the water for the production of ammonia — thus helping 
forward the organic matter in its natural course of decay, and enabling 
it to fulfil its destined purposes in reference to vegetable life. 

3°. But the ammonia which is thus disengaged in the soil by decay- 
ing organic matter, though not immediately worked up, so to speak, by 
living plants, is not permitted to escape in any large quantity into the 
air. The soil, as I have already stated, is usually absorbent enough to 
retain it in its pores for an indefinite period of time. And as in nature 
and upon the earth's surface the elements of matter are rarely permitted 
to remain in a state of repose, the ammonia, though retained apparently 
inactive in the soil, is yet slowly uniting with a portion of the surround- 
ing oxygen and forming nitric acid (Lee. VIII. , § 5, note). When no 
other base is present, this nitric acid, as it is produced, unites with some 
of the ammonia itself which still remains, forming nitrate of ammonia- 
hut if potash or lime be present within its reach, it unites with them in 
preference, and forms the nitrate qfjwtash or of lime. 

But lime, if present, is not an inactive spectator, so to speak, of this 
slow oxidation of ammonia. On the contrary, it promotes this final 
change, and by being ready to unite with the nitric acid as it forms, in- 
creases and accelerates its production, at the expense of the ammonia 
which it had previously been instrumental in evolving. 

4°. One other important action of lime, by which the same com- 
pounds of nitrogen are produced in the soil, may in this place be most 
properly noticed. It is a chemical law of apparently extensive applica- 
tion, that when one elementary substance is undergoing a direct chemi- 
cal union with a second in the presence of a third, a tendency is impart- 
ed to the third to unite also with one or with both of the other two, al- 
though in the same circumstances it would not unite with either, if pre- 
sent alone. Thus, when the carbonaceous matter of the soil is under- 
going oxidation in the air — that is, combining with the oxygen of the at- 
mosphere — it imparts a tendency to the nitrogen also to unite with oxy- 
gen, which when mixed with that gas alone* it has no known disposi- 
tion to do. The result of this is the production of a small, and always a 
variable, proportion ofnitric acid during the decomposition in the soil, of or- 
ganic matter even, which itself contains no nitrogen. 

Again, it is an equally remarkable chemical law, that elementary 
bodies which refuse to combine, however long we may keep them to- 
gether in a state of mixture, will yet unite readily when presented to 
each other in what is called by chemists the nascent state — that is, at 
the moment when one or other of them is produced oris separated from 
a previous state of eombination. 

Thus when the organic matter of the soil decomposes water in the 
presence of atmospheric air, its carbon unites with the greater part 
of the oxygen and hydrogen which are set at liberty, and at the same 
time with more or less of the oxygen of the atmosphere — but at the 

* The atmosphere consisting, as you will recollect, of nitrogen and oxygen (Lee. II., § 4). 
35 



412 HOW THESE CHEMICAL CHANGES BENEFIT VEGETATION. 

eame instant the nitrogen of the atmosphere, which is everywhere pre- 
sent, seizes a portion of the hydrogen and forms ammonia. Thus a va- 
riable, and in any one limited spot, a minute, but over the entire surface 
of the globe, a large quantity of ammonia is produced during the oxi- 
dation even of the purely carbonaceous portion of the organic matter of 
the soil. 

Now in proportion as the presence of lime promotes this decay of 
vegetable and other organic matter in the soil — in the same proportion 
does it promote the production of ammonia and nitric acid, at the expense 
of the free nitrogen of the atmosphere, and this may be regarded as one 
of the valuable and constant purposes served by the presence of calca- 
reous matter in the soil. 

§ 30. How these chemical changes directly benefit vegetation. 

You will scarcely, I think, inquire how all these interesting chemical 
changes which attend upon the presence of lime in the soil are directly 
useful to vegetation, and yet it may be useful shortly to answer the 
question. 

1°. Lime combines with the acid substances already existing in the 
soil, and thus promotes the decomposition of vegetable matter which 
those acid substances arrest. The further decompositions which ensue 
are attended at every step by the production either of gaseous com- 
pounds — such as carbonic acid and light carburetted hydrogen — which 
are more or less abundantly absorbed by the roots and leaves of plants, 
and thus help to feed them — or of acid and other compounds, soluble 
in water, which, entering by the roots, bear into the circulation of the 
plant not only organic food, but that supply of lime also which healthy 
plants require. 

2°. The changes it induces upon substances in which nitrogen is 
present are still more obviously useful to vegetation. It eliminates am- 
monia from the compounds in which it exists already formed, and pro- 
motes its slow conversion into nitric acid, by which the nitrogen is ren- 
dered more fixed in the soil. It disposes the nitrogen of more or less 
inert organic matter to assume the form of ammonia and nitric acid, in 
which state experience has long shown that this element is directly fa- 
vourable to the growth of plants. 

3°. It influences in an unknown degree, the nitrogen of the atmos- 
phere to become fixed in larger proportion in the soil, in the form of nitric 
acid and ammonia, than would otherwise be the case, and this it does 
both by the greater amount of decay or oxidation which it brings about in 
a given time, and by the kind of compounds which, under its influence, 
the organic matter is persuaded to form. The amount of nitrogenous 
food placed within reach of plants by this agency of lime will vary with 
the climate, with the nature of the soil, with its condition as to drain- 
age, and with the more or less liberal and skilful manner in which it is 
farmed. 

§ 31. Why lime must he kept near the surface. 
Nor will you fail to see the important reasons why lime ought to be 
kept near the surface of the soil — since 

1°. The action of lime upon organic matter is almost nothing in the 



ACTION OF LIME UPOI^ SALII^E SUBSTANCES. 413 

absence of air and moisture. If the lime sink, therefore, beyond the 
constant reach of fresh air, its efficacy is in a great degree lost. 

2°. But the agency of the light and heat of the sun, though I have 
not hitherto insisted upon their action — are scarcely less necessary to the 
full experience of the benefits which lime is capable of conferring. The 
light of the sun accelerates nearly all the chemical decompositions that 
take place in the soil — while some it appears especially to promote. 
The warmth of the sun's rays ma}-- penetrate to some depth, but their 
light can only act upon the immediate surface of the soil. Hence the 
skilful a griculturist will endeavour, if possible, to keep some of his 
lime at least upon the very surface of his arable land. Perhaps this in- 
fluence of light might even be adduced as an argument in favour of the 
frequent application of lime in small doses, as a means of keeping a 
portion of it always within reach of the sun's rays ; and this more es- 
pecially on grass lands, to which no mechanical means can be applied 
for the purpose of bringing again to the surface the lime that has sunk. 

There are, at the same time, as you will recollect, good reasons also 
why a portion of the lime should be diffused through the body of the 
soil, both for the purpose of combining with organic acids already ex- 
isting there, and with the view of acting upon certain inorganic or min- 
eral substances, which are either decidedly injurious, or by the action 
of lime may be rendered more wholesome to vegetation. 

In order that this diffusion may be effected, and especially that lime 
may not be unnecessarily wasted where pains are taken by mechanical 
means to keep it near the surface, an efficient system of under-drainage 
should be carefully kept up. Where the rains that fall are allowed to 
flow ofT the surface of the land, they wash more lime away the more 
carefully it is kept among the upper soil — but where a free outlet is af- 
forded to the waters beneath, they carry the lime with them as they sink 
towards the subsoil, and have been robbed again of the greater part of 
it before they escape into the drains. Thus on drained land the rains 
that fall aid lime in producing its beneficial efTects, while in undrained 
land they in a greater or less degree counteract it. 

§ 32. Action of lime vpon the inorganic or mineral matter of the soil. 

Though the main general agency of lime is exerted, as w» have seen, 
upon the organic matter it meets with, yet it often also produces direct 
chemical changes upon the mineral compounds existing in the soil, which 
are of great importance to vegetation. Thus 

1^. Lime, either in the mild or in the caustic state, possesses the pro- 
perty of decomposing the sulphate of iron, which especially abounds in 
peaty soils, and in many localities so saturates the subsoil as to make it 
destructive to the roots of plants. Sprengel mentions a case where the 
first year's clover always grew well, while in the second year it always 
died away. This, upon examination, was found to be owing to the fer- 
ruginous nature of the subsoil, which caused the death of the plant as 
soon as the roots began to penetrate it. 

When salts of iron exist in the soil, a dressing with lime will bring 
the land into a wholesome state without other aid. The lime will com- 
bine with the acid, and form gypsum, if it is the sulphate of iron that 
is present, while the first 0)4ide of iron which is set free will, by expo- 



^^H 



414 LIxME DECOMPOSES SULPHATES AND SILICATES, SETS FREE 

sure to the air, be converted into the second or red oxide, in which state 
this metal is no longer hurtful to vegetation. 

When these salts are to be decomposed and removed from the sub- 
soil, lime must be aided by the subsoil plough and the drain. Unless 
an outlet beneath be provided for the surface water, by which the rains 
may be enabled to wash away slowly the noxious substances from the 
subsoil, even the addition of a copious dose of lime will only produce a 
temporary improvement. 

2°. Lime decomposes also the sulphates of magnesia and of alumi- 
na, both of which are occasionally found in the soil, and, being very so- 
luble salts, are liable to be taken up by the roots in such quantity as to 
be hurtful to the growing plants. When soils which contain any of the 
three salts I have mentioned have once been limed or marled, it is in 
vain to add gypsum in the hope of favouring the clover croj), since the 
lime, in decomposing the sulphates, has already formed an abundant 
supply of this compound for all the purposes of vegetation. 

S"^. Among the earthy constituents of the soil, we have already seen 
that there often exist fragments of felspar and of other minerals derived 
from the granitic and trap rocks, which contain potash or soda in the 
state of silicates. These silicates we know to be slowly decomposed 
by the agency of the carbonic acid of the air (Lee. X., § 1), and their 
alkali set free in a soluble state. This decomposition is said to be 
prompted by the presence of lime (p. 361). 

Again, the stalks of the grasses and the straw of the corn-bearing 
plants contain much silica in combination with potash and soda. In 
farm-3^ard manure, therefore, much of these silicates is present, and 
when mixed with the soil, there appears little reason to doubt that they 
are of much benefit to the growing crops. On these silicates, in the 
presence of carbonic acid and moisture, the lime acts as it does upon 
the mineral silicates. It aids in the liberation of the potash and soda, 
and thus promotes the performance of those important functions which 
these alkalies are destined to exercise in reference to vegetable growth 

While the alkali is set free the lime itself combines with the silica, 
and hence one source of the sihcate of lime which, as I have already 
mentioned to you (p. 380), usually exists in sensible quantity in our cul- 
tivated soils. It has been stated by Sprengel* as one reason why the 
addition of lime must be repeated so frequently upon some soils in which 
silica abounds, that an insoluble silicate of lime is formed, which is of 
no use to vegetation. But the silicates of lime are slowly decomposed 
by the agency of the carbonic acid of the air and of decaying vegetation, 
and to this cause in a previous lecture (Lee. XII., § 4), I have ascribed 
much of the fertile character of the trap and syenitic soils, and of their 
beneficial action when laid on as a manure. 

4°. Potash and soda exist to some extent in clay soils in combination 
with their alumina. The presence of lime has a similar influence in 
setting the alkalies ^ree from this state of combination also. 

5°. Alumina has the property of combining readily with many vege- 
table acids, and in the clay soils exercises a constant influence, similar 
in kind to that of lime and other alkaline substances, in persuading the 

* Lehre voin Dilngei; p. 310. 



ALKALINE SUBSTANCES, AND DECOMPOSES COMMON SALT. 415 

organic matter to those forms of decay in which acid compounds are 
more abundantly produced. Hence, clay soils almost always contain a 
portion of alumina in combination with organic matter. This organic 
matter is readily given up to lime, and by the more energetic action of 
this substance is sooner made available to the wants of new races of plants. 

6°. I shall bring under your notice only one other, but a highly im- 
portant, decomposing action, which lime exercises in soils that abound 
in vegetable matter. In the presence of decaying organic substances 
the carbonate of lime is capable of slowly decomposing common salt, 
producing carbonate of soda and chloride of calcium. It exercises also 
a similar decomposing effect, even upon the sulphate of soda, and, ac- 
cording to Berthollet,* incrustations of carbonate of sodaf are observed 
on the surface of the soil, wherever carbonate of lime and com- 
mon salt are in contact with each other. If we consider that along all 
our coasts common salt may be said to abound in the soil, being yearly 
sprinkled over it by the salt sea winds — that generally, along the same 
coasts, the application of sulphates produces little sensible effect upon 
the crops, and that, therefore, in all probability they abound in the soil, 
derived, it may be, from the same sea spray — we may safely conclude, 
I think, that the decomposition now explained must take place extensively 
in all those parts of our island which are so situated, if lime in any of 
its forms either exists naturally or has been artificially added to the land. 
The same must be the case also in those districts where salt springs oc- 
cur, and generally over the new red sand-stone formation, in which sea 
salt more especially occurs. 

And if we further consider the important purposes which the carbo- 
nate of soda thus produced may serve in reference to vegetation — that it 
may dissolve vegetable matter and carry it into the roots — that it may 
form soluble silicates, and thus supply the necessary siliceous matter to 
the stems of the grasses and other plants — and that rising, as it naturally 
does, to the surface of the soil, it there, in the presence of vegetable 
matter, provokes to the formation of nitrates, so wholesome to vegetable 
life — we may regard the decomposing action of lime by which this car- 
bonate is produced aa among the most valuable of its properties to the 
practical farmer, wherever circumstances are favourable for its exercise, 

§ 33. Action of lime on animal and vegetable life. 

It is only necessary to allude, in conclusion, to one or two other useful 
purposes which lime is said to serve in reference to animal and vegeta- 
ble life. Thus 

1"^. It is said to prove fatal, especially in the caustic state, to worms, 
to slugs,* and to many insects injurious to the farmer, and to destroy 
their eggs and larvae. In Scotland it has been found in some instances 
to check the ravages of the fly. On the other hand, in the state of car- 
bonate, it is propitious to the growth of the land snail and similar crea- 
tures which bear shells. In highly limed land the former may be seen 
crowded at the roots of the hedges, from which they make frequent in- 

* Dumas Traite de Chemie, ii., p. 334. 

t Of Trona or Natron, which is a sesqui carbonate of soda. 

t When the wheat crop is attacked by slugs above ground, nothing will do so much good 
as slaked lime, sown over the crop before sunrise.— Hillyard, Royal Agricultural Journal, 
iii., p. 302. 

35* 



416 LIME KILLS INSECTS AND SEEDS. 

cursions upon the young crops, and are, I believe, especially hurtful to 
the turnips. 

2°. It is found to prevent smut in wheat. For this purpose the seed 
is steeped in lime, and afterwards dried with slaked lime, or lime wa- 
ter is poured upon the heap of corn, which is turned over, and left for 
24 hours (Hillyard). 

3°. It is also said to prevent the rot and foot-rot in sheep fed upon 
pastures on which, before liming, the slock was liable to be affected by 
these diseases (Prideaux). 

4°. In regard to its action upon living plants, it is certain that it ex- 
tirpates certain of the coarser grasses from sour pastures and brings up a 
tenderer herbage ; but practical men appear to differ in regard to its ef- 
fects upon the roots and seeds of the more troublesome weeds. Accord- 
ing to some, the addition of lime to a compost, or to the soil, will kill 
the roots of weeds and render unproductive such noxious seeds as may 
happen to be present. According to others (p. 405), this is a mistake. 
I believe the truth to be, that lime will lead to their destruction and de- 
cay, if the circumstances are favourable or if proper pains be taken to 
effect it. But air and moisture are necessary to insure this, as they are 
to effect the rapid decay of dead organic matter. If the ingredients of 
the compost be duly proportioned, or if the dose of lime added to the 
land be sufficiently large, and if in each case the mixture be frequently 
turned, the final destruction of roots and seeds may in general be safely 
calculated upon. 

§ 34. Use of silicate of lime. 

There is one compound of lime which, though occurring occasionally 
in all soils, has not hitherto been applied to the improvement of the land 
even in localities where it most abounds. This compound is the silicate 
of lime. I have already directed j-^our attention to the presence of this 
compound in the trap rocks, and to the fertile character which it imparts 
to the soils which are formed by the naiural degradation of these rocks. 

In those districts where the smelting of iron is carried on, the first 
slag that is obtained consists in great part of silicate of lime. This slag 
accumulates in large quantities, and is employed in some districts for 
mending the roads. It is not unM'orthy the attention of the practical 
farmer — as an improver of his fields — especially where caustic lime is 
distant and expensive, or where boggy and peaty soils are met with in 
which vegetable matter abounds. On such land it may be laid in large 
quantity. It will decompose slowly, and while it imparts to the soil 
solidity and firmness, will supply both lime and silica to the growing 
crops, for a long period of time. 



I have thus drawn your attention to the most important topics connected with the use of 
lime, so efficacious an instrument in the hands of the skilful and improving farmer for ame- 
liorating the condition and increasing the productiveness of his land. If I have appeared to 
dwell long upon this subject, it is because of the value which I know to be attached by 
practical men to a correct exposition of the virtues of lime and of the theory by which 
its effects are to be explained. I believe that in the theoretical part I have been able to 
point out to you the leading chemical principles upon which its influence depends — if any 
thing is still dark, it is because our knowledge is not yet complete. A few years more, 
and we may hope to have the mists which har.g over this, as over many other branches 
of agricultural chemistry, in a great measure cleared away. 



LECTURE XVII. 

Of organic manures. — Vegetable and animal manures. — Green manuring; ploughing in of 
spurry, the white lupin, the vetch, buckwheat, rape, rye, borage. — Natural green manu- 
ring. — Improvement of the soil by laying down to gra-ss and by planting. — Use of sea- 
weed. — Dry vegetable manures : dry straw, chaff, rape dust, malt-dust, saw-dust, cotton 
eeeds, dry leaves. — Decayed vegetable matter: use of peat, tanners' bark, and com[)osts 
of vegetable matter — Charcoal powder, soot — Relative value, theoretical, and practical, 
of different vegetable manures. 

By organic manures are understood all those substances either of 
vegetable or of animal origin, which are applied to the land for the pur- 
pose of increasing its fertility. It will be convenient to consider these 
two classes of organic substances separately. 

The parts of vegetables may be applied to the soil in three different 
forms — in the green, in the dry, and in the more or less naturally de- 
cayed, fermented, or artificially decomposed state. 

§ ^- Of green manuring, or the application of vegetable matter in the 

green state. 

By green manuring is meant the ploughing in of green crops in their 
living state — or of green vegetables left or spread upon the land for the 
^turpose. 

1°. We have seen in the preceding lecture how important air and 
water are to the decomposition of organic matter. Now green vegetable 
substances contain within themselves much water, undergo decomposi- 
tion more readily, therefore, than such as have been dried, and are more 
immediately serviceable when mixed with the soil. 

2'^. In the sap of plants also there generally exist certain compounds 
containing nitrogen, which not only decompose very readily themselves, 
but have the property of persuading or inducing the elements of the 
other organic matters, with which they are in contact, to assume new 
forms or to enter into new chemical combinations. Hence, the sap of 
plants almost invariably undergoes more or less rapid decomposition 
even when preserved from the contact of both air and water. When 
this decomposition has once comiTienced in the sap it is gradually propa- 
gated to the woody fibre and to the other substances of which the mass 
of the stems and roots of plants is composed. Hence, recent vege- 
table matter will undergo a comparatively rapid decomposition, even 
when buried to some depth beneath the soil — and the elements of which 
it consists will form new compounds more or less useful to living plants, 
in circumstances where dry and where many forms even of partially 
decomposed vegetable matter would undergo no change whatever. 

3°. Further — when green vegetable matter is allowed to decay in the 
open air, it is gradually resolved more or less completely into carbonic 
acid, which escapes into the air and is so far lest. But when buried be- 
neath the surface, this formation of carbonic acid proceeds less rapidly, 
and other compounds — preparatory to the final resolution into carbonic 
acid and water — are produced in greater quantity and linger in the soil. 



418 GREEN VEGETABLES READILY DECAY, AND ENRlCfi THE SOIL. 

Thus by burying vegetable substances in his land in their green state, 
the practical man actually saves a portion of the organic food of plants, 
which would otherwise so far. run to waste. 

4°. Finally. Green vegetable substances, by exposure to the air, 
gradually give up a portion of the saline matter they contain to the 
showers of rain that fall. This more or less escapes and is lost. But if 
buried beneath the soil this saline matter is restored to the land, and 
where the green matter thus buried is in the state of a growing crop, 
both the organic and inorganic substances it contains are more equally 
diffused through the soil than they could be by any other known process. 

On one or other of these principles depend nearly all the special ad- 
vantages which are known to follow from green manuring and from the 
employment of green vegetable matter in the preparation of composts. 

§ 2. Important practical results obtained by green manuring. 

But this explanation of the principles on which the efficacy of green 
manuring depends, does not fully illustrate the important practical results 
by which, in many localities, it is uniformly followed. 

Let us glance at these results. 

1°. The ploughing in of green vegetables on the spot where they 
have grown may be followed as a method of manuring and enriching 
all land, where other manures are less abundant. Growing plants bring 
up from beneath, as far as their roots extend, those substances which are 
useful to vegetation — and retain them in their leaves and stems. By 
ploughing in the whole plant we restore fo the surface what had previ- 
ously sunk to a greater or less depth, and thus make it more fertile than 
before the green crop was sown. 

2°. This manuring is performed with the least loss by the use of 
vegetables in the green state. By allowing them to decay in the open 
air, there is, as above stated, a loss both of organic and of inorganic matter 
— if ihey be converted into fermented (farm-yard) manure, there is also 
a large loss, as we shall hereafter see; and the same is the case, if they 
are employed in feeding stock, with a view to their conversion into ma- 
nure. In no other form can the same crop convey to the soil an equal 
amount of enriching matter as in that of green leaves and stems. "Where 
the first object, therefore, in the farmer's practice is, so to use his crops 
as f.o enrich his land — he will soonest effect it by ploughing them in in 
the green state, 

3°. Another important result is, that the beneficial action is almost 
immediate. Green vegetables decompose rapidly, and thus the first crop 
which follows a green manuring is benefitted and increased by it. But 
partly for this reason also the green manuring — of corn cropped land — 
if aided by no other nianure, must generally be repeated every second 
year. 

4°. It is said that grain crops which succeed a green manuring are 
never laid — and that the produce in grain is greater in proportion to the 
straw, than when manured with fermented dung. 

6°. But it is deserving of separate consideration, that green manuring 
is especially adapted for improving and enriching soils which are poor 
in vegetable matter. The principles on which livingplants draw a part 
—sometimes a large part— of their sustenance from the air, have already 



GREEN MANURE MOST USEFUL TO POOR AND SANDY SOIL. 419 

been discussed, and I may presume that you sufficiently understand the 
principles and admit the fact. Living plants, then, contain in their sub- 
stance not only all they have drawn up from the soil, but also a great 
part of what they have drawn down from the air. Plough in these hving 
plants, and you necessarily add to the soil more than was taken from 
it — in other words, you make it richer in organic matter. Repeat the 
process w^ith a second crop and it becomes richer still — and it would be 
difficult to define the limit beyond which the process could no further be 
carried. 

Is there any soil then, in the ordinary climates of Europe, which is be- 
yond the reach of this improving process? Those only are so on which 
plants refuse to grow at all, or on which they grow so languidly as to 
extract from the air no more than is restored to it again by the natural 
decay of the organic matter which the soils already contain. 

But for those plants which grow naturally upon the soil, agricultural 
skill may substitute others, which will increase more rapidly, and pro- 
duce a larger quantity of green leaves and stems for the purpose of being 
buried in the soil. Hence, the selection of particular crops for the pur- 
pose of giving manuring — those being obviously the fittest which in the 
given soil and climate grow most rapidly, or ivhich produce the largest 
quantity of vegetable matter in the shortest time and at the smallest cost. 

§ 3. (y the plants which in different soils and climates are employed 
for green manuring. 

On this principle is founded the selection oi different plants in different 
soils and climates for the purpose of green manuring. That which 
in Italy will yield the largest produce of leaves and stems, at the least 
cost, and in the shortest time, may not do so in the North of England or 
of Germany — and that which will enrich a poor clay or an exhausted 
loam may refuse even to grow, in a heahhy manner, upon a drifting sand. 

1°. Spurry (Spergula Arvensis). — It is to poor dry sandy soils that 
green manuring has been found most signally beneficial, and for such 
soils no plant has been more lauded than spurry. It may either be 
sown in autumn on the corn stubble or after early potatoes, and 
ploughed in in spring preparatory to the annual crop, or it may be 
used "to replace the naked fallow, which is often hurtful to lands of so 
light a character. In the latter case, the first sowing may take place 
in March, the second in May, and the third in July — each crop being 
ploughed in to the depth of three or four inches, and the new seed then 
sown and harrowed. When the third crop is ploughed in, the land is 
ready for a crop of winter corn. 

Von Voght* states that by such treatment the worst shifting sands 
may be made to yield remunerative crops of rye — that the most worth- 
less sands are more improved by it than those of a better nattjral qual- 
ity — that the green manuring every other year not only nourishes suf- 
ficiently the alternate crops of rye, but gradually enriches the soil— and 
that it increases the effect of any other manure that may subsequently 
be put on. He adds, also, that spurry produces 'often as much improve- 
ment if eaten off by cattle as if ploughed in, and that when fed upon. 

• VoTtheile der griinen Bediingung. 



420 USE OF THE VETCH, BUCKWHEAT, ETC. 

this plant, either green or in the slate of hay, cows not only give more 
milk, but of a richer quality. 

2^. [Vhiie Lvpins. — In Italy, and in the south of France, the while i 
lupin is extensively cuUivated as a green manure. In Germany, also, II 
it has been found to be one of those plants by which 'unfruitful sandy 
soils may be most speedily brought into a productive stale. The supe- 
riority of this plant for the purpose of enriching the soil depends unon 
its deep, roots, which descend more than two feet beneath the surface— 
upon its being little injured by drought, and little liable to be attacked 
by insects — on its rapid growth — and upon its large produce in leaves 
and stems. Even in the North of Germany it is said to yield, in three 
and a half to four months, 10 to 12 tons of green herbage. It grows in 
all soils except such as are marly and calcareous, is especially partial 
to such as have a ferruginous subsoil, and besides enriching, also opens 
stiff clays by its strong stems and roots. 

3°. The Vetch is inferior in many of its qualities to the white lupin-^ 
yet in Southern Germany it is often sown on the stubble, and ploughed 
in after it has been touched with the frost, and has begun to decay. In 
England also the winter tare ploughed in early in spring has been found 
highly advantageous.* It is a more precarious, however, and a more 
expensive crop than either of the former, and requires a better soil for 
its successful growth. 

4°. Buck- Wheat is also too uncertain a crop, and the high price of 
its seed renders it inferior in value to spurry on sandy soils. It is su- 
perior to this latter plant, however, on poor heaths. In Southern Ger- 
many it is sown on the stubble, and ploughed in when it is 18 or 20 
inches high. 

5°. Rape can only be sown upon a soil which is already in some 
measure rich, but it has the advantage of continuing to grow very late 
in the autumn, and of beginning again very early in spring. It sends 
down deep roots also, and loosens clayey soils by its thick stems. In 
the light soils of Alsace it is sown after early peas and potatoes, and 
manures the land for the succeeding crop of wheat or rye. 

5°. .Rye is pronounced by Von Voght to be the best of all green ma- 
nures for sandy soils, but it is also the most expensive. It is a very 
stire crop and begins to grow very early in the spring, br.t it is not deep 
rooted. It has been used with advantage in Northern Italy and in Ger- 
many. 

6°. Turnips have been sown in Sussex with good effect as a stubble 
crop for ploughing in in spring, and in Norfolk and elsewhere the por- 
tions of the turnip bulbs which are left when they are eaten off by sheep 
contribute, when ploughed in, to enrich the land for the barle}^ that is to 
follow. Turnip tops are in many places ploughed in with much benefit 
to the land.f Potatoe tops also might be dug or ploughed in with equal 
advantage. 

7°. Borage has been strongly recommended in Germany, and especi- 
ally by Lampadius. It is stated by this experimenter that borage draws 
from the air ten times as much of the elements of its organic matter as 

* British Husbandry, I. , p. 407. 

t " I find no better way of manuring for wheat after turnips, than ploughing in the tops 
while still green, as soon as the turnips are taken off the land." — Mr. Campbell, of Craigie. 



1GREEN MANURING SOITABLE FOR AFTER-CROPS OF C0R:V. 421 

It does from the soil, and that therefore it is admirably fitted for enrich- 
ing the land on which it grows. 

8*^. Red Clover is often ploughed in as a manure. On the Rhine it 
is sown for this purpose, being ploughed in before it begins to flower. 
In French Flanders two crops of clover are cut, and the third ploughed 
in, and in some parts of the United States of North America the clover 
which alternates with the wheat crop is ploughed in as the only manure.* 
White Clover is not so valuable for this purpose, for neither is it so deep 
rooted nor does it yield so large a crop of stems and leaves. 

9°. Old grass. — Perhaps the most common form of green manuring 
practised in tliis country is that of ploughing up grass lands of various 
ages. The green matter of the sods serves to manure the after- crop, 
and renders the soil capable of yielding a richer return at a smaller ex- 
pense of manure artificially added. 

In regjrd to all these forms of green manuring it is to be observed that 
they enrich the soil generally, and are therefore well fitted to prepare it 
for after-cr(»ps of corn ; they will not fit it, however, for a special crop, 
such as turnips, which requires to be unnaturally forced or pushed for- 
ward at a particular period of its growth. 

§ 4. Will green manuring alone prevent land from becoming exhausted ? 

If by green manuring is meant the growing of vegetable matter upon 
one field, and ploughing it in green into another, as is sometimes done, 
it may be safely said that, when judiciously practised, land may by this 
single process be secured for an indefinite period against exhaustion. 
But if we plough in only what the land itself produces, and carry off oc- 
casional crops of corn, the time will ultimately come when any soil 
thus treated will cease to yield remunerating crops. A brief considera- 
tion of the subject will satisfy you of this. 

Suppose a loose sand to be improved by repeatedly sowing and 
ploughing in crops of spurry or white lupins, the green leaves and stems 
fix the floating elements of the atmosphere, and enrich the soil with or- 
ganic matter, while the roots, more or less deep, bring up saline matters 
to the surface, and thus supply to the plant what is no less necessary to 
its healthy growth. But the rains yearly wash away from the surface, 
and the corn crops remove a portion of this saline matter. This portion 
the crops grown for the purpose of green manuring yearly renew by 
fresh supplies from beneath. But no subsoil contains an inexhaustible 
store of those saline substances which plants require. Hence, though by 
skilful green manuring waste land may be brought to a remunerative 
: state of fertility, it will finally relapse again into a state of nature, if no 
I other methods are subsequently adopted for maintaining its productive- 
ness. The process may be a slow one, and practical men may be un- 
willing to believe in the posGibility of a result which does not exhibit it- 
I self ■'vithin the currency of a single lease, or during a single life-time— 
yet few things are more certain than that in general the soil must sooner 
I or latei rtceive supplies o^ saline manure in one form or another, or else 
I must ultimately become unproductive. It may be considered as a proof 
of this fact that, in all densely peopled countries in which agriculture 
I has been skilfully prosecuted, the manufacturing of such manures has 

' Barclay's Agricultural Tour in the United States. 



422 



OF THE PRACTICE OF GREEN MANURING. 



become an important branch of business, giving employment to many 
hands, and attordmg an mvestraent to much capital. ■ 

The following table, in addition to other particulars, exhibits the rela- 
tive proportions o^ dry organic and saline matter, capable of being added 
to the surface soil by a few of those plants which are employed for the 
purposes of remanunng : — i j ^ 



Kind of Plant. 



Spurry 
White Lupin 

Vetch 

Buck- wheat 
Rape . 



.Vverage 

produce 

per imp. 

acre. 



lbs. 
6,500 
25,000 

11,000 

8,000 

16,000 



1000 lbs. contai! 
in the green statt 



Organic 

Matter. 



lbs. 
199 

188 

233 
170 
214 



Saline 
Matter. 

lbs. 

2] 

12 

17 
10 
16 



Depth of 
Roots. 



inches. 
12 to 15 
24 to 26 

15 to 20 

12 to 15 

1 



Crops 

in a 

Year. 



2 or 3 
1 or 11 

2 

2 

1 or H 



Soil for which they are 
fitted. 



Dry, loose, sandy. 
Any except marly or 

calcareous. 
Strong soil. 

Dry, sandy, or moorish, 
-lich soil. 



§ 5. O/* the practice of green manuring. 

bearin mFJd-'^^ ^'^°P''*'° °^ ^'''" manuring it is of importance to 

l'^. That a sufficient quantity of seed must be sown to keep the 

groundwell covered, one of the attendant advantages of stubble^crips 

'o wieds ^ ^^ ^^ " ''°^ '^'"" and prevent it frL becoming a prey 

1 ^'* JJ"^' I^^ P^f."*^ ''"^^^ ^" ^^ "^ow" o'- harrowed, and at once 
ph3ughed in heforethey come into full fencer. The flow;r-leaves Ze 
off nitrogen into the air, and as this element is supposed especiallv m 
promote the growth of plants, it is desirable to retain as much of i^ n 
the plant and sod as possible. Another reason is that, if allowed to 
wrwe'eds' " '"' "'^'^ ^'^' ^"^ ^^^— ds infest thl land 

t>, ^^:i. ^^^^ *^u^ should be ploughed in to the depth of 3 or 4 inches only 
that they maybe covered sufficiently to prevent waste, and >4t be wi"hfn 
reach of the air, and of the early roots of the succeeding crop. 

§6. Of natural manuring with recent vegetable matter. 
Besides the method of ploughing in, which may be distinguished as 
ar^ficial green mantirmg -there is another mode in which refentveee' 
table matter is employed in nature for the purpose of enrichir/the soil 
The natural grasses grow and die upon a meadow or pasture field and 
though that which IS above the surface may be mowedVor hay or cron 

ttlTmaurbltaT T?"'^ -<^.g-d-"y ^^d to theTt^amhrof 
yegetaDie matter beneath. The same is the case to a greater or leJex- 
tent with all the artificial corn, grass, and leguminouf cropi we^^^^^^^ 



WEIGHT OF ROOTS LEFT IN THE SOIL. 423 

this end, but many plants, when in whole or in part eaten upon the field, 
leave enough in the soil materially (o improve the condition of the land 
— while in all cases those are considered as the least exhausting, to which 
are naturally attached the largest weight of roots. Hence, the main 
reason wh}^ poor lands are so much benefitted by being laid down to 
grass, and v/hy an intermediate crop of clover is often as beneficial to the 
after-crop of corn as if the laud had lain in naked fallow.* 

An interesting series of experiments on the relative weights of the 
roots and of the green leaves and stems of various grasses, made by 
Hlubek,f throws considerable light upon their relative efficacy in en- 
riching the soil by the vegetable matter they diffuse through it in the 
form of roots. The grasses were grown in beds of equal size (180 square 
feet), in the agricultural garden at Laybach, and mown on the fourth 
year after sowing, just as they were coming into flower. The roots were 
then carefully taken up, washed, and dried. The results were as follows : 

Weiffht of 
Produce in Produce in Roots, ^ry Roots 

Kind of Grass. f " n ,- " v to 100 lbs. 

Grass. Hay. Fresh. Dry. of Hay. 

1. Festuca Elatior— T^^Z Fescue-grass 124 lbs. 36 lbs. 56 lbs. 22 lbs. 61 lbs. 

2. Festuca Ovina — Sheep's Fescue- grass, 90 30 — 80 266 

3. Phleum Frditeiise— Timothy-grass, 90 25 56 17 60 

4. Dactylis Glomerata — Rough Cock's- 

foot, 202 67 — 22| 33 

5. Lolium Percnne — Perennial Rye- 

grass, 50 17 — 50 300 

6. Alopecurus Fx^i&nsis-Meadoiv Fox- 

tail, 106 35 — 24 70 

7. Triticum Repens — Creeping Couch 

or Quicken-grass, . . . .120 60 — 70 116 

8. Pea Annua — Annual Meadow-grass, — — — — 111 

9. Bromus Mollis and Racemosus — 

Soft and smooth Brome-grass, . — — — — 105 

10. Anthoxanthum Odoratum — Sweet- 
scented Vernal-grass, ... — — — — 93 

A mixture of white clover, of ribwort, of hoary plantain, and of couch- 
grass, in an old pasture field, gave 400 lbs. of dry roots to 100 lbs. of hay 
— and in a clover field, at the end of the s^^cond year, the fresh roots 
were equal to one-third of ihe whole weight of green clovor obtained at 
three cuttings— one in the first, and two in the second year — while in 
the dry state there were 56 lbs. of dry roots to every 100 lbs. of clover hay 
which had been carried off. 

The fourth column of the above table shows how large a quantity of 
vegetable matter some of the grasses impart to the soil, and yet how un- 
like the different gra.sses are in this respect. The sheep's-fescue and 
the perennial rye-grass — besides the dead roots, which detach them- 
selves from time to time — leave, at the end of the fouiih year, a weight 
o^ living roots in the soil which is equal to three times the produce of 
that year in hay. If we tate the mean of all the above grasses as an 
average of what we may fairly expect in a grass field — then the amount 

* If the third crop be ploughed in, the land is actually enriched. — Schwertz. 
t Erndhrung der PJlanzen, p. 466. 

36 



424 MANURING BY THE ROOTS 01* CLOVER, AND feY 

of living roots left in the soil when a four-y earmold grass field is ploughed 
up, will he equal to one-sixth more than the weight of that yearns crop. 

In an old pasture or meadow field again, when ploughed up, the 
living roots left are equal to four times the weight of that yearns hay crop. 
If a ton and a half of hay have been reaped — then about six tons of dry 
vegetable matter remain in the soil in the form of roots. 

In the case of clover, at the end of the second year the quantity of 
dry vegetable matter left in the fbrrn of roots is equal to upwards of one- 
half the weight of the whole hay which the clover has yielded. Sup- 
pose there be three cuttings, yielding 4 tons of hay, then 2 tons of dry 
vegetable matter are added to the soil in the form of roots, when the clover 
stubble is ploughed up. 

But the quantity of roots, like that of green produce, is dependent 
upon a variety of circumstances. It will sometimes, therefore, be 
greater and sometimes less than is above stated. It may be received 
as a rule — not without exceptions perhaps, yet still as a general rule — 
that whatever causes an increased produce above ground, will cause a 
corresponding increase in the growth of roots. Thus nitrate of soda, 
which gives us a larger yield of hay, makes the roots also stronger and 
deeper, and the sward tougher and more difficult to plough {Appendix, 
No. III). Hence it is that the farmer is anxious that his clover crop 
should succeed, not merely for the increased amount of green food or of 
hay it will give him, but because it will secure him also a better after- 
crop of corn. 

This burying of recent vegetable matter in the soil, in the form of 
living and dead roots of plants, is one of those important ameliorating 
operations of nature which is always to some extent going on, where- 
ever vegetation proceeds. It is one by which the practical man is often 
benefitted unawares, and of which — too often without understanding the 
source from whence the advantage comes — he systematically avails 
himself in some of the most skilful steps he takes with a view to the im- 
provement of his land. 

§ 7. Improvement of the soil by laying down to grass. 

One of the most common of these methods of improvement is that 
of laying down to grass. This may be done for two, three, or four 
years only, or for an indefinite period of time. In the latter case, the 
land is said to be laid down permanently, or to permanent pasture. 

1°. Teinporary pasture or meadoio. — If the land be sown with grass 
and clover-seeds, only as an alternate crop between two sowings of corn, 
the eflfect is fully explained by what has been already stated {§ 6). 
The roots which are left in the soil enrich the surface with both organic 
and inorganic matter, and thus fit it for bearing a better after-crop of 
corn. 

If, again, it bs left to grass for three or five years, the same efTect is 
produced more fully, and therefore this longer rest from corn is better 
fitted for soils which are poor in vegetable matter. The quantity of 
organic matter which has accumulated becomes greater every year, in 
consequence of the annual death of stems and roots, and of the soil being 
more closely covered, but tliis increase is probably never in any one 
after-year equal to that which takes place during the first. The quan- 



LAYING DOV/iV TO GRASS. — PERMANENT PASTURE. 425 

tity of roots which is produced during the first year of the young plants' 
growth must, we may reasonably suppose, be greater than can ever 
afterwards be necessary in an equal space of lime. Hence, one good 
year of grass or clover will enrich the soil more in proportion to the time 
expended, than a rest of two or three years in grass, if annually moived. 

Or, if instead of being mown, the produce in each case be eaten off 
by stock, the result will be the same. That which lies longest will be 
the richest when broken up, but not in an equal proportion to the time 
it has lain. The produce of green parts, as well as of roots, in the ar- 
tificial grasses, is generally greatest during the first year after they are 
sown, and therefore the manuring derived from the droppings of the 
stock, as well as from the roots, will be greatest in proportion during the 
first year. That farming, therefore, is most economical — where the 
land will admit of it — which permits the clover or grass seeds to occupy 
the land for one year only. 

But if, after the first year's hay is removed, the land be pastured for 
two or three years more, it is possible that each succeeding year may 
enrich the surface soil as much as the roots and stubble of the first 
year's hay had done ; so that if it lay three years it might obtain three 
times the amount of improvement. This is owing to the circumstance 
that the whole produce of the field remains upon it, except what is car- 
ried off by the stock when removed — but very much, it is obvious, will 
depend upon the nature of the soil, and upon the selection of the seeds 
being such as to secure a tolerable produce of green food during the 
second and third years. 

2°. Permanent j^cisture or meadow. — But when land is laid down to 
permanent grass it undergoes a series of further changes, which have 
frequently arrested attenlion, and which, though not difficult to be un- 
derstood, have often appeared mysterious and perplexing to practical 
men. Let us consider these changes. 

a. When grass seeds are sown for the purpose of forming a perma- 
nent sward, a rich crop of grass is obtained during the first, and per- 
haps also the second year, but the produce after three or four years les- 
sens, and the value of the pasture diminishes. The plants generally 
die and leave blank spaces, and these again are slowly filled up by the 
sprouting of seeds of other species, which have either lain long buried 
in the soil or have been brought thither by the winds. 

This first change, which is almost universally observed in fields of 
artificial grass, arises in part from the change which the soil itself has 
undergone during the few years that have elapsed since the grass seeds 
were sown, and in part from the species of grass selected not being such 
as the soil, at any time, could permanently sustain. 

b. When this deterioration, arising from the dying out of the sown 
grasses, has reached its utmost point, the sward begins gradually to im- 
prove, natural grasses suited to the soil spring up in the blank places, 
and from year to year the produce becomes greater and greater, and the 
land yields a more valuable pasture. Practical men often say that to 
this improvement there are no bounds, and that the older the pasture 
the more valuable it becomes. 

But this is true only within certain limits. It may prove true for the 
entire currency of a lease, or even for the lifetime of a single observer, 



426 THE SCIL AND GRASSES CONTIIMUALLY CHANGE. 

but it is not generally true. Even if pastured by stock only and never 
mown, the improvement will at length reach its limit or highest point, 
and from this time the value of the sward will begin to diminish. 

c. This, again, is owing to a new change which has come over the 
soil. It has become, in some degree, exhausted of those substances 
which are necessary to the growth of the more valuable grasses — less 
nutritive species, therefore, and such as are less willingly eaten by cattle, 
take their place. 

Such is the almost universal process of change which old grass fields 
undergo, whether they be regularly mown or constantly pastured only — 
provided they are left entirely to themselves. If mown they begin to 
fail the sooner, but even when pastured they can be kept in a state of 
full productiveness only by repeated top-dresoings, especially of saline 
manure — that is, by adding to the soil those substances which are neces- 
sary to the growth of the valuable grasses, and of which it suffers a 
yearly and unavoidable loss. Hence, the rich grass lands of our fathers 
are found now in too many cases to yield a herbage of little value. 
Hence, also, in nearly all countries, one of the first steps of an improv- 
ing agriculture is to plough out the old and failing pastures, and either to 
convert them permanently into arable fields, or, after a few years' crop- 
ping and manuring, again to lay them down to grass. 

But when thus ploughed out, the surface soil upon old grass land is 
found to have undergone a remarkable alteration. When sown with 
grass seeds, it may have been a stiff, more or less grey, blue, or yellow 
clay — when ploughed out it is a rich, brown, generally light and friable 
vegetable mould. Or when laid down it may have been a pale-coloured, 
red, or yellow sand or loam. In this case the surface soil is still, when 
turned up, of a rich brown colour — it is lighter only and more sandy 
than in the former case, and rests upon a subsoil of sand or loam instead 
of one of clay. It is from the production of this change that the inn- 
provement caused by laying land down to grass principally results. In 
what does this change consist ? and how is it effected ? 

If the surface soil upon stiff clay lands, which have lain long in grass, 
be chemically examined, it will be found to be not only much richer in 
organic matter, but often also poorer in alumina than the soil which 
formed the surface when the grass seeds were first sown upon it. The 
brown mould which forms on lighter lands will exhibit similar difTeren- 
ces when compared with the soil on which it rests; but the proportion 
of alumina in the latter being originally small, the difference in respect 
to this constituent will not be so perceptible. 

The effect of this change on the surface soil is in all cases to make it 
more rich in those substances which cultivated plants requirs, and there- 
fore more fertile in corn. But strong clay lands derive the further im- 
portant benefit of being rendered more loose and friable, and thus more 
easily and more economically cultivated. 

The mode in which this change is brought about is as follows: — 

1°. The roots, in penetrating, open and loosen the subjacent stiff clay. 
Diffusing themselves every where, they gradually raise, by increasing 
the bulk, of the surface soil. The latter is thus converted into a mix- 
ture of clay and decayed roots, which is of a dark colour, and is neces- 
sarily more loose and friable than the original or subjacent unmixed clay. 



AGENCY OF THE RAINS A^'D WINDS. 497 

2°. But this admixture of roots effects the chemical composition as 
well as the state of aggregation of the soil. The roots and stems of the 
grasses contain much inorganic — earthy and? saline — matter (Lee. IX., 
§ 1), which is gathered from beneath, wherever the roots penetrate, and 
is by them sent upwards to the surface. A ton of hay contains about 
170 lbs. of tills inorganic matter (Lee. X., §3). Suppose the roots 
to contain as much, and that the total annual produce of grass and roots 
together amounts to four tons, then about 680 lbs. of saline and earthy 
matters are every year worked up by the living plants, and in a great 
measure permanently mixed with the surface soil. Some of this, no 
doubt, is carried off by the cattle that feed, and by the rains that fall, 
upon the land — some remains in the deeper roots, and some is again, 
year after year, employed in feeding the new growth of grass — still a 
sufficient quantity is every season brought up from beneath, gradually 
to enrich the surface with valuable inorganic matter at the expense of 
the soil below. 

3°. Nor are mechanical agencies wanting to increase this natural 
difference between the surface and the under soils. The loosening and 
opening of the clay lands by the roots of the grasses allow the rains 
more easy access. The rains gradually wash out the fine particles of 
clay that are mixed with the roots, and carry them downwards, as they 
sink towards the subsoil. Hence the brown mould, as it forms, is slow- 
ly robbed of a portion of its alumina, and is rendered more open, while 
the under soil becomes even stiffer than before. This sinking of the 
alumina is in a great measure arrested when the soil becomes covered 
with so thick a sward of grass as to break the force of the rain-drops or 
of the streams of water by which the land is periodically visited. 
Hence the soil of some rich pastures contains as much as 10 or 12, of 
others as little as 2 or 3 per cent, of alumina. 

4°. The winds also here lend their aid. From the naked arable 
lands, when the weather 's dry, every blast of wind carries off a portion 
of the dust. This it suffers to fall again as it sweeps along the surface 
of the grass fields — the thick sward arresting the particles and sifting the 
air as it passes through them. Everywhere, even to remote districts, 
and to great elevations, the winds bear a constant small burden of earthy 
matter;* but there are few practical agriculturists who, during our high 
winds, have not occasionally seen the soil carried off in large quantities 
from their naked fields. Upon the neighbouring grass lands this soil 
falls as a natural top-dressing, by which the texture of the surface is 
gradually changed and its chemical constitution altered. 

5°. Another important agency also must not be overlooked. In grass 
lands insects, and especially earth-worms, abound. These almost 
nightly ascend to the surface, and throw out portions of finely-divided 
earthy matter. On a close shaven lawn the quantity thus spread over 
the surface in a single night often appears surprising. In the lapse of 
years the accumulation of the soil from this cause must, on old pasture 
fields, be very great. It has often attracted the attention of practical 

* It has been observed that on spots purposely sheltered frem the wind and rain on every 
side, the quantity of dust that is collected, when pressed down, is in 3 years equal to one line, 
or in 36 years to one inch in thickness, — Sprengel, Lehre vom Dilnger, p. 443. 

36* 



428 WHY ARTIFICIAL PASTURES DETERIORATE. 

men,* and so striking has it appeared to some, that they have been in- 
clined to attribute to the slow but constant labour of these insects, the 
entire formation of the fertile surface soils over large tracts of country. f 

I have directed your attention to these causes chiefly in explanation 
of the changes which by long lying in grass the surface of our stifTclay 
lands is found to undergo. But they apply equally to other soils also — 
the only difference being that, in the case of such as are already light 
and open, the change of texture is not so great, and therefore does not so 
generally arrest the attention. 

Upon this subject I may trouble you further with two practical remarks : 

1°. That the richest old grass lands — those which have remained 
longest in a fertile condition — are generally upon our strongest clay soils 
(the Oxford and Lias clays, Lee. XL, § 8). This is owing to the 
fact that such soils naturally contain, and by their comparative imper- 
meability re-tain, a larger store of those inorganic substances on which 
the valuable grasses live. When the surface soil becomes deficient in 
any of these, the roots descend further into the subsoil and bring up a 
fresh supply. But these grass lands are not on this account exempt 
from the law above explained, in obedience to which all pastured lands, 
when left to nature, must ultimately become exhausted. They must 
eventually become poorer ; but in their case the deterioration will be 
slower and more distant, and by judicious top-dressings may be still 
longer protracted. 

2'^. The natural changes which the surface soil undergoes, and espe- 
cially upon clay lands when laid down to grass, explain why it is so dif- 
ficult to procure, by means of artificial grasses, a sward equal to that 
which grows naturally upon old pasture lands. As the soil changes 
upon our artificial pastures, it becomes better fitted to nourish other spe- 
cies of grass than those which we have sown. These naturally spring 
up, therefore, and cover the soil. But these intruders are th^m^selves 
not destined to be permanent possessors of the land. The soil under- 
goes a further change, and new species again appear upon it. We can- 
not tell how often different kinds of grass thus succeed each other upon 
the soil, but we know that the final rich sward which covers a grass field 
when it has reached its most valuable condition, is the result of a long 
series of natural changes which time only can bring about. 

The soil of an old pasture field, which has been ploughed up, is made 
to undergo an important change both in texture and in chemical constitu- 
tion, before it is again laid down to grass. The same grasses, therefore, 
which previously covered it will no longer flourish, even when they are 
sown. Hence the unwillingness felt by practical men to plough up 
their old pastures — but hence, also, the benefit which results from the 
breaking up of such as are old, worn out, or covered with unwholesome 
grasses. When again converted into pasture land, new races appear, 
and a more nourishing sward is produced.} 

' The permanence of a fine carpeting of rich sweet grass upon a portion of his farm is as- 
cribed (by Mr. Purdie) to " the spewings of the worms, apparently immenGely numerous, 
which incessantly act as a rich top-dressing." — Prize Essays of the Highland Society, I., p. 191. 

t Geological Transactions. 

X For an excellent article on the snperior feeding qualities of recent artificial grasses over 
many old pasture lands, by Mr. Buswell, of Kingcaussie, see the Quarterly Journal of Agri- 
culture, N , p. 783. 



IMPROVEMENT OF THE SOIL BY PLANTING OF TREES. 429 

§ 8. Improvement of the soil by the planting of trees. 

It has long been observed by practical men, that when poor, thin, un- 
productive soils have been for some time covered with wood, their quality 
materially improves. In the intervals of the open forest, they will pro- 
duce a valuable herbage — or when cleared of trees they may for some 
time be made to yield profitable crops of corn. 

This fact has been observed in almost every country of Europe, but 
the most precise observations upon the subject with which I am ac- 
quainted are those which have been made in the extensive plantations of 
the late Duke of Athol. These plantations consist chiefly of white 
larch {Larix Europcea). and grow upon a poor hilly soil, resting on 
gneiss, mica-slate, and clay-slate (Lee. XL, § 8). In six or seven years 
the lower branches spread out, become interlaced, and completely over- 
shadow the ground. Nothing, therefore, grows upon it till the trees are 
24 years old, when the spines of the lower branches beginning to fall, 
the first considerable ttiinning takes place. Air and light being thus 
re-admitted, grasses (chiefly holcus mollis and lanatus) spring up, and a 
fine sward is gradually produced. The ground, which previously was 
worth only 9d. or Is. per acre as a sheep pasture, at the end of 30 years 
becomes worth from 7s. to 10s. per acre. 

The soil on this part of the Duke's estate is especially propitious to 
the larch — and, therefore, this tree both thrives best and in the greatest 
degree improves the soil. Thus in oak copses, cut every 24 years, the 
soil becomes worth only 5s. or 6s. per acre, and this during the last six 
years only. Under an ash plantation, the improvement amounts to 2s. 
or 3s. per acre; under Scotch fir, it does not exceed 6d. an acre — while 
under spruce and beech the land is worth less than before.* 

The main cause of this improvement, as of that which is produced by 
laying down to grass, is to be found in the natural manuring with recent 
vegetable matter, to which the soil year by year is so long subjected. 
Trees differ from grasses only in this, that while the latter enrich the 
soil both by their roots and by their leaves, the former manure its surface 
only by the leaves which they shed. 

The leaves of trees, like those of grasses, contain much inorganic mat- 
ter, and this when annually spread upon the ground slowly adds to the 
depth as well as to the richness of the soil. Thus the leaves of the fol- 
lowing trees, when dried in the air, contain respectively of inorganic 
matterf : — 

April. 

Oak . . . . — 

Ash . . , . — 

Beech .... — 

Birch . . . . — 

Elm .... — 

Willow . . . — 
White Larch . . 6 J. per cent. 

Scotch Fir . . . — " If " — «< 

In looking at the differences among these numbers — especially in the 

* Mr. Stephens in the Transactio7is of ike Ilighkmd Society, xi., p. 189; aU'O Loqcioji's 
^nci/clopadia of Agriculture, p. 1346. 
t Sprengel, Che7nie far Landtcir!he, n.,Y)a.ssim, 



August. 


November. 


5 per cent. 


4^ 


per cent 


6i 


— 


(( 


7 


64 


u 


5 <' 




<< 


m '^ 


— . 


« 


8i « 


-^ 


«? 


<£ 




C( 



430 RELATIVE EFrECTS OF DIFFERENT KINDS OF TREES. 

case of tlie elm and of the Scotch fir— one would naturally suppose that 
the diversity of their effects in improving the land is in some measure 
to be ascribed to the quantity and kind of the inorganic matter which 
the leaves of these several trees contain. And to this cause, no doubt, 
some effect is to be ascribed in localities where all the trees thrive 
equally . 

But upon the quantity of leaves produced, as much in general will 
depend, as upon the relative proportions of organic and inorganic mat- 
ter which these leaves may respectively contain. And as the quantity 
of leaves is always greatest where the tree flourishes best or finds a most 
propitious soil— the improvement of the soil itself, by any particular 
tree, will be always in a great measure determined by its fi'tness to pro- 
mote the growth of that kind of tree. 

On the soil planted by the Duke of Athol, the larch shot up luxuri- 
antly, while the Scotch fir lingered and languished in its growth. Thus 
the quantity of leaves produced and annually shed by the former was 
vastly greater than by the latter tree. Had the Scotch fir thriven better 
than the larch, the reverse might have been the case, and the value of 
the soil might have been increased in a greater proportion by planta- 
tions of the former tree. 

Other special circumstances also will account for the relative degrees 

of improvement produced by the larch and by some of the other trees 

for example, the oak. In the oak copse the soil in 16 years become 
worth 6s. or 8s. an acre. If, therefore, instead of being cut down for 
their bark at the end of 24 years, the trees had been allowed to grow up 
into an oak forest, the permanent improvement of the pasture, even on 
this soil, would probably have been at least as great as under the larch. 
The above experiments, therefore, are in reality not so decisive in re- 
gard to the relative iinproving jwiver of the several species of trees as 
they at first sight appear, the most rational natural rule by which 
our practice should be guided seems to be contained in these three pro- 
positions — 

1°. That the soil will be most improved by those trees which thrive 
best upon it. 

2°. Among those which thrive equally, by such as yield the largest 
produce of leaves, and — 

3°. Among such as yield an equal weight of leaves, by those whose 
leaves contain the largest proportion of inorganic matter— which bring 
up from beneath, that is, and spread over the surface in largest quantity, 
the materials of a fertile soil. 

The mode in which the lower branches of the larch spread out and 
overshadow the surface is not without its influence upon the ultimate 
improvement which the soil exhibits. All vegetation being prevented, 
the land, besides receiving a yearly manure of vegetable mould, is made 
to lie for upwards of 20 years in uninterrupted naked fallow. It is 
sheltered also from the beating of the rain drops, which descend slowly 
and gently upon it, bearing principles of fertility instead of washing out 
the valuable saline substances it may contain. 

Beneath the overshadowing branches of a forest, the soil is also pro- 
tected from the wind, and to this protection Sprengel attributes much 
of that rapid improvement so generally experienced where lauds are 



MANURING WITH SEA-WEED. 431 

covered with wood. The winds bear along particles of earthy matter* 
which they deposit again in the still forests; and thus gradually form a 
soil even on the most naked places. This slow general cause of accu- 
mulalion may not be without its effect, and should not be forgotten, but 
it evidently affords no explanation why, in the same range of country, 
the soil which is covered by forests of one kind should improve more 
rapidly than those which are sheltered by trees of another species. 

§ 9. Of the use of sea-weed as a manure. 

Among green manures of great value and extensive application there 
remains to be noticed the sea-weed or sea-ware of our coasts. The 
marine plants of which it consists differ from the green vegetables grown 
upon land, — 

1"^. By the greater rapidity with which they undergo decay. When 
laid as top-dressings upon the land they melt down, as it were, and in a 
short time almost entirely disappear. Mixed with soil into a compost 
or with quick-lime, they speedily crumble down into a black earth, in 
which little or no trace of the plant can be perceived. 

2°. By the greater proportion of saline or other inorganic matter 
which these plants, in their dry state, contain. It is these substances 
which are obtained in the form of kelp when dry sea-weeds are burned 
in the air. 

We have seen (Lee. X., §3), that the quantity of ash left by 1000 lbs. of 
our more usually cultivated grasses, in the dry state, varies from 5 to 
nearly 10 per cent., but the fucus vesiculosus, which is reckoned the 
most valuable for the manufacture of kelp, gives upwards of 160 lbs. of 
ash from 1000 lbs. of the dry plant. This ash, according to Fagerstrom, 
consists of — 

Gypsum 63-4 lbs. 

Carbonate of Lime 34*1 " 

Iodide of Sodium '2'7 " 

Other Salts of Soda 29-9 " 

Silica, Oxide of Iron, and earthy Phosphates, 31-1 " 



161-2f 

This ash contains less potash, but more soda and gypsum, than those 
of the grasses (Lee. X., §3), and hence, as you will readily understand, 

* See note, p. 427. 

+ Berzelius Arsberdtfelse, 1824, p. 225. — If we compare the composition of this ash with 
that of the several varieties of kelp, given in page 356, it will be seeni to differ from them very 
considerably. But kelp is always manufactured from a mixture of different plants in vary- 
ing proportions, and hence one cause of the diversity of composition among different sam- 
ples of this substance. 

Sprengel states {Lehre vom Diivger, p. 277), that the fucus vesiculosus contains only 16 

Fer cent, of water. I do not know whether this is the result of experiments of his own, but 
have not introduced it inlo the text, because it appears to me inconsistent with the remark- 
able manner in which sea-weed shrivels up when dried, and with its little permanence as a 
manure. " If an acre of land is completely covered with it, after a few days of dry weather, 
the whole would not weigh 500 lbs. The fibrous parts reduced to mere threads alone re- 
main — so that it is like manuring land witli cobioebs" (Dr. Walker). This would seem to 
imply the presence of a larger quantity of water in fresh sea-weed than in green grass, and 
consequently a less efficacy as a manure when applied in equal weights. According to 
Boussingault, the fucus digitatus contains 40 per cent, of water, and the fucus sacchariims 
76 per cent, when newly taken from the sea, and 49 per cent, after being dried in the air. 



432 MODE IN WHICH SEA-WKED IS APPLIED. 

may be expected to exercise a somewhat diflTerent influence upon vege- 
tation. 

It is of importance, however, to bear in mind that the saline and other 
inorganic matters which are contained in the sea-weed we lay upon our 
fields, form a positive addition to the land. If we plough in a green 
crop where it grew, we restore to the soil the same saline matter only 
which the plants have already taken from it during their growth, while 
the addition of sea-weed imparts to it an entirely new supply. It 
brings back from the sea a portion of that which the rivers are constant- 
ly carrying into it, and is thus valuable in restoring, in some measure, 
what rains and crops are constantly removing from the land. 

Sea-weed is collected along most of our rocky coasts — and is seldom 
neglected by the farmers on the borders of the sea. In the Isle of 
Thanet, it is sometimes cast ashore by one tide and carried off by the 
next ; — so that after a storm the teams of the farmers may be seen at 
work even during the night in collecting the weed, and carrying it be- 
yond the reach of the sea.* In that locality, it is said to have doubled 
or tripled the produce of the land. On the Lothian coasts, a right of 
way to the sea for the collection of sea-ware increases the value of the 
land from 25s. to 30s. an acre.f In the "Western Isles it is extensively 
collected and employed as a manure J — and on the North-east coast o' 
Ireland, the farming fishermen go out in their boats and hook it up from 
considerable depths in the sea.§ 

It is applied either immediately as a top-dressing, especially to grass 
lands — or it is previously made into a compost with earth, with lime, or 
with shell-sand. Thus mixed with lime, it has been used with advan- 
tage as a top-dressing for the young wheat crop ;|| and with shell-sand, it 
is the general manure for the potatoe crop among the Western island- 
ers. IT It may also be mixed with farm-yard manure or even with peat 
moss, both of which it brings into a more rapid fermentation. In some 
of the Western Isles, and in Jersey, it is burned to a light, more or less 
coaly powder, and in this form is applied successfully as a top-dressing 
to various crops. There is no reason to doubt that the most econcmical 
method is to make it into a compost with absorbent earth and lime, or to 
plough it in at once in the fresh state. 

In the Western Islands one cart load of farm-yard manure is consid- 
ered equal in immediate effect — upon the first crop, that is — to 2^ of fresh 
sea -weed, or to 1^ after it has stood two months in a heap. The sea- 
weed, however, rarely exhibits any considerable action upon the second 
crop. 

Sea-weed is said to be less suited to clay soils, while barren sand has 
been brought into the state of a fine loam by the constant apj)licaiion of 
sea-weed alone, for a. long series of years.** 

Conflicting opinions are given by different practical men, in regard to 
the crops to which it is best suited. But the explanation of most of 

* British Husbandry, IT., p. 418. 
t Kerr's Berwickshire, p 377. 

J " Sea weeds constitute one-half of Hebridean manures, and nine-tenths of those of the 
remoter Islands " — Macdonald's Agriculture of the Hebrides, p. 401. 
§ Mrs. Hall's Irelaytd. 
11 British Husbandry, II., p. 419. 

T Transactions of the Highland Society, 1S42-3, p. 766. 
'" Macdonald's ire6rides, p. 407. 



I 



t:SE OF STRAW AS A MANURE. 433 

ihese and similar discordances is to be found in the answers to the three 
following questions — what substances does the crop specially require? — 
how many of these abound in the soil? — can the manure we are about 
to use supply all or any of the remainder? If it can, it may be expected 
to do good. Thus simply and closely are the kind of crop, the kind of 
soil, and the kind of manure, in most cases, connected together. 

§ 10. Of manuring with dry vegetable substances. 

The main general difference between vegetable matter of the same 
Jcindf and cut at the same age, when applied as a manure in the green 
and in the dry state, consists in this — that in the former it decomposes 
more rapidly, and, therefore, acts more speedily. The total effect upon 
vegetation will probably in either case be very nearly the same. 

But if the dry vegetable matter have been cut at a more advanced 
age of the plant or liave been exposed to the vicissitudes of the weather 
while drying, it will no longer exhibit an equal efficacy. A ton of dry 
straw, when unripe, will manure more richly titan a ton of the same straw 
in its ripe state — not only because the sap of the green plant contains 
the materials from which the substance of the grain is afterwards formed 
— but, because, as the 'plant ripens, the stem restores to the soil a por- 
tion of the saline, especially of the alkaline, matter it previously con- 
tained (Lee. X., § 5). After it is cut, also, every shower of rain that 
falls upon the sheaves of corn or upon the new hay, washes out some of 
the saline substances which are lodged in its pores, and thus diminishes 
its value as a fertilizer of the land. These facts place in a still stronger 
light the advantages which necessarily follow from the use of vegetable 
matter in the recent state, for manuring the soil. 

1°. Dry straw. — It is in the form of straw that dry vegetable matter is 
most abundantly employed as a manure. It is only, however, when 
already in the ground in the state of stubble, that it is usually ploughed 
in without some previous preparation. When buried in the soil in the 
dry state, it decomposes slowly, and produces a less sensible effect upon 
the succeeding crop; it is usually fermented, therefore, more or less com- 
pletely, by an admixture of animal manure in the farm-yard before it is 
laid upon the land. During this fermentation a certain unavoidable 
loss of organic, and generally a large loss of saline matter, also takes 
place.* It is, therefore, theoretically true of dry, as it is of green, ve- 
getable matter, that it will add most to the soil, if it be ploughed in with- 
out any previous preparation. 

Yet this is not the only consideration by which the practical man 
must be guided. Instead of a slow and prolonged action upon his crops, 
he may require an immediate and more powerful action for a shorter 
time, and to obtain this he may be justified in fermenting his straw with 
the certainty even of an unavoidable loss. Thus the disputed use of 
short and long dung becomes altogether a question of expediency or of 
practical economy. But to this point I shall again recur when treating 
of farm-yard manure in the succeeding lecture. 

2°. Chaff partakes of the nature of straw, but it decomposes more 
slowly when buried in the soil in the dry state. It is also diflScult to 

• See in the succeeding lecture the section upon mixed animcU and vegetaJble manures. 



434 ACTION OF RAPE-DUST ON WHEAT AND BEANS. 

bring into a state of fermentation, even when mixed with the liquid ma- 
nure of the farm -yard. 

3°. Rape-dust. — When rape seed is exhausted of its oil, it comes 
from the press in the form of hard (rape) cakes, which, when crushed 
to powder, form the rape-dust of late years so extensively employed as 
a manure. It is occasionally mixed with farm-yard dung, and applied 
to the turnip crop, hut its principal employment has hitherto been, I be- 
lieve, as a top-dressing for the wheat crop, either harrowed in with the 
seed in October or applied to the young corn in spring. 

Rape-dust requires moisture to bring out its full fertilizing virtues; 
hence it is chiefly adapted to clay soils or to such as rest upon a stiflf 
subsoil. It is seldom applied, therefore, to the barley crop, and even 
upon wheat it will fail to produce any decidedly good effect in a very 
dry season. Several interesting circumstances have been experimen- 
tally ascertained in regard to the action of rape-dust, to which it is pro- 
per to advert: — 

a. That in very dry seasons it may produce little benefit upon tur- 
nips, potatoes, and other crops, while in the same circumstances the ef- 
fect of guano may be strikingly beneficial. Thus in one experiment, 
made in 1842, upon unmanured land sown with turnips — 

16 cwt. of rape-dust gave 3| tons of bulbs per acre. 
2 cwt. of guano gave 5 do. 

Unmanured gave . 3^ do. i 

And in another, in the same season, upon unmanured land — 
1 ton of rape-dust gave 141 tons of bulbs per acre. 
3 cwt. of guano gave 23^ do. 

UnmanUred gave 12|* do. 

Again, upon potatoes, planted without other manure, in 3 experi- 
ments the produce per acre, in tons, was as follows: — 

Unmanured. 1 ton Rape-dust. 3 cwt. Guano. 4 cwt. Guano. 
Whiet Don Potatoes . — 12^ 18^ — 

Red Don Potatoes . . 6f 10 — I4i 

Connaught Cups . . 5| 13 — 13| 

In none of the above experiments did the action of the large quantity 
of rape-dust equal that of the comparatively small quantity of guano — 
though, from being buried in the soil, the difference was less striking in 
the case of the potatoe crops. 

b. Rape-dust may actually cau.se the crop to be less than the land 
alone would naturally produce — if in a dry season it be laid on in any 
considerable quantity. 

Thus in 1842, in an experiment upon Oats, made at Lennox Love— 
16 cwt. of rape-dust gave 45 bushels. 

2 cwt. of guano gave 68 do. 
Unmanured soil gave 49 do. 
In this property of injuring the crop, when rain does not happen to 
fall, rape-dust resembles very much those saline substances which, as 
we have seen, may often be applied with much advantage to the land. 

c. Yet it would appear to exercise less of this evil influence upon 
wheat and beans, even in similar circumstances. Thus in the same 

• See Appendix, No. VIII. 



THE qUANTlTY MUST NOT BE TOO GnEAT. 435 

season, 1842, and in the same locality, Lennox Love, a crop of wheat, 
with — 

16 cwt. of rape-dust gave 51 bushels per acre. 

2 cwt. of guano gave 48 do. 

Unmanured gave A7^ do. 

And a crop of beans, with — 

16 cwt. of rape-dust gave 38 bushels. 

2 cwt. of guano gave 35|^ do. 
Unmanured gave 30 do. 

In both of these cases, notwithstanding the drought, the rape-dust 
improved the crop, and though not sufficiently so to pay the cost of the 
application, yet to a greater extent than the same quantity of guano. 
It is deserving of investigation, therefore, whether rape-dust be more 
especially adapted to wheat and beans. Even in favourable seasons it 
may possibly prove more economical than guano as a manure for these 
two crops.* 

d. But even in favourable seasons, and to the wheat crop, there is 
reason to believe that rape-dust cannot be economically applied in more 
than a certain, perhaps variable, quantity per acre. Thus four equal 
plots of ground (nearly half an acre each), sown with wheat, were top- 
dressed with rape-dust in different proportions with the following results : 

With 7 cwt. the produce was 26 bushels of market corn. 

With 10 cwt. the produce was 28 do. 

With 15 cwt. the produce was 29i do. 

With 26 cwt. the produce was 27j do. 

Unmanured the produce was 22if do. 

In this experiment not only was the crop diminished when more than 
15 cwt. was added, but the increased produce was not sufficient to defray 
the additional cost of the application, when more than 7 cwt. of rape-dust 
was put on. 

e. It may be noticed as another curious fact, that the action of rape- 
dust is dependent upon the presence or absence of certain other substan- 
ces in the soil. Common salt and sulphate of soda, when mixed with it 
under certain circumstances, lessen the effect which it would produce 
alone, and the same will probably happen when it is applied, without 
admixture, to soils in which these saline com pounds happen to be already 
present. Some remarks upon this interesting point will be found in the 
Appendix, No. VIII. 

4°. Linlseed, poppy-seed, cotton-seed, and cocoa-nut cakes. — The cake 
which is left when other oils are extracted from the seeds or fruits in 
which they exist is also, in almost every case, useful as a manure. Thus 
the seeds of the cotton plant yield an oil and leave a cake which is now 
used as a manure in the United States, though little known as yet, I be- 
lieve, in England. The cocoa-nut cake is employed in Southern In- 
dia partly in feeding cattle and partly as a manure for the cocoa-nut tree 
itself. Some trials have recently been made with it among ourselves, 
but I am ignorant of the precise results. In this country lintseed cake 
is made in large quantity, but as it is relished by cattle, is fattening, and 

• See Appendix, No. VITI. 
t British Husbandrt/, I., p. 412. 
37 



436 USE OF MALT-DUST, DRY LEAVES, AND PEAT, AS MANURES. 

enriches the droppings of the stock fed upon it, it is seldom applied di- 
rectly to the land. In France and some parts of Belgium, where the 
poppy is largely cultivated for the oil yielded by its seeds, the cake 
which these seeds leave is highly esteemed as a manure. 

5°. Malt-dust. — When barley is made to sprout by the maltster, and 
is afterwards dried, the small shoots and rootlets drop off, and form the 
substance known by the name of malt-dust. One hundred bushels of 
barley yield 4 or 5 bushels of this dust. It is sold at the rale of from 5s. 
to 8s. a quarter, and has been applied with success as a top-dressing to 
the barley and wheat crops. It may also be drilled in with turnips or 
dusted over the young grass in spring. 

6°. Saw-dust is usually rejected by the agriculturist, in consequence 
of the difficulty which is generally experienced in bringing itinto a state 
of fermentation. It decomposes slowly when ploughed into the soil in | 
its dry state, but it nevertheless gradually benefits the land, and should f 
not, therefore, be permitted in any case to run to waste. It forms an 
excellent absorbent also for liquid manures of any kind, which it pre- » 
serves from sinking too rapidly when they are to be applied to porous, | 
sandy, or chalky soils, while these liquids again hasten the decomposition 
of the saw-dust and augment irs immediate effect upon (he land. In lo- 
calities favourable for the collection of sea-weed, it may also be more 
rapidly fermented by an admixture with this substaKce. Saw-dust 
forms an ingredient in some of the mixed manures which have recently 
come into use (see Appendix, No. VIII., Exp. B.) 

7°. Dry leaves may either be dug into the land at once, or may be 
laid up in heaps, when they will gradually decay, and form, in most 
cases, an enriching manure. They gradually improve the soil (as we 
have already seen, p. 429), on which they annually fall, but the same 
quantity of leaves will do more good if collected and immediately dug 
in, or if made into a compost heap, than if left to undergo a slow natural 
decay on the surface of the land. 

§ 12. Of the use of decayed vegetable matter as a manure. 

The most abundant forms of partially decayed vegetable matter 
which come within the reach of the practical farmer, are peat and tan- 
ner's bark. 

1°. Peat. — To soils which are deficient in vegetable matter, it is 
clear that a judicious admixture of peat must prove advantageous, be- 
cause it will supply some at least of those substances which are neces- 
sary to the production of a higher degree of fertility. But peat decays 
very slowly in the air, and hence its apparent effect when mixed with 
the soil is very small. It may gradually ameliorate its quality, espe- 
cially if the soil be calcareous, but it will not immediately prepare the 
land for the growth of any particular crop. But if the obstacles to its 
further decomposition be removed — that is, if by artificial means its de- 
cay be promoted — then its immediate and apparent effect upon the soil 
is increased, and it becomes an acknowledged fertilizing manure. Dif- 
ferent methods have been successfully practised for bringing it into this 
more rapid state of decay or fermentation. 

a. The half-dried peat may be mixed with from one-fourth to one- 
half of its weight of fermenting farm-yard manure — the whole heap be- 



i 



FERMENTATION OF PEAT AND TANNEr's BARK. 437 



ing carefully covered over with a layer of peat to prevent the escape of 
fertilizing vapours. By this method — first introduced to public notice 
by the late Lord Meadowbank — the entire mixture is gradually brought 
into an equable state of heat and fermentation, and as a manure for the 
turnip crop, is said to be as efficacious as an equal weight of unmixed 
farm-yard manure. 

b. Or the liquid manure of the farm-yard may be employed for the 
same purpose, either in whole or in part. If the heap of mixed peat 
and dung be watered occasionally whh the liquid manure, the fermen- 
tation will be more speedily effected, and at a less expense of common 
farm-yard dung. Or the half-dried peat may be used unmixed, as an 
absorbent for the liquid of the farm-yard, by which, without other aid, 
it will be brought into a state of fermentation whh comparative 
rapidity. 

c. Or instead of the litiuid manure, the ammoniacal liquor of the gas- 
works may be employed, with less prominent benefit certainly, but still 
with great advantage. 

d. Or the peat may be mixed whh from one-sixth to one-fourth of its 
bulk of fresh sea-weed, the rapid decay of which will gradually reduce 
the entire heap into a fertilizing mass.* 

e. Or rape-dust in the proportion of 1 ton to 30 cubic yards may be 
mixed with the half-dried peat from two to six weeks before the time of 
sowing the turnip crop. The fermentation of the rape-dust takes place 
so quickly, that this short time is usually sufficient to convert the whole 
into a uniform and rapidly decaying mass. 

In short, it is only necessary to mix half-dried peat with any sub- 
stance which undergoes rapid spontaneous decomposition — when it will 
more or less speedily become infected with the same tendency to decay, 
and will thus be rendered capable of ministering to the growth of culti- 
vated plants. 

2°. Tanner's hark is still more difficult to reduce or to bring into a 
rapid state of decomposition. Any of the methods above recommended 
for peat, however, will to a certain extent succeed also with the spent 
bark of the tan pits. But in the case of substances so solid and refrac- 
tory as the lumps of bark are, the admixture of a quantity of lime and 
earth, so as to form a compost heap, is perhaps the most advisable 
mode of procedure. The way in which lime promotes the decay of 
woody fibre in such heaps has already been explained (see p. 382.) 

§ 13. Use of charred vegetable matters as a manure. 

Soot and charcoal are the principal substances of this class which 
have been more or less extensively emploj'ed for the purpose of increas- 
ing the productiveness of the land. 

1°. Soot is a complicated and variable mixture of substances pro- 
duced during the combustion of coal. Its composition, and consequent- 
ly its effects as a manure, vary with the quality of the coal, with the 
wa}' in which the coal is burned, and with the height of the chimney in 
which it is collected. 

• British Husbandry, II , p. 417- 



438 COMPOSITION OF SOOT — ITS EFFECTS UPON Rt£-GRASS. 

Soot has not been analyzed since the year 1826, when a variety ex- 
amined by Braconnot was found by him to consist in a thousand parts of 

Ulmic acid 7 (a substance resembling that portion of the vegetable 
matter of the soil which is soluble in caustic potash — (see Lee. 

XIII., § 1) . . . . 3020 

A reddish brown soluble snbstance, containing nitrogen, and yield- 
ing ammonia when heated 2000 

AsboUne 5*0 

Carbonate of lime, with a trace of magnesia (probably derived in 

part from the sides of the chimney) 1466 

Acetate of lime 565 

Sulphate of lime (gypsum) 500 

Acetate of magnesia . . 5*3 

Phosphate of lime, with a trace of iron 150 

Chloride of potassium 3*6 

Acetate of potash 41*0 

Acetate of ammonia 2*0 

SiUca(sand) . . .* 9-5 

Charcoal powder . . 38*5 

Water 1250 



1000* 
The earthy substances which the soot contains are chiefly derived 
from the walls of the chimney, and from the ash of the coal, part of 
which is carried up the chimney by the draught. These, therefore, 
must be variable, being largest in quantity where the draught is strong- 
est and where the earthy matter or ash in the coal is the greatest. The 
quantity of gypsum present depends upon the sulphur contained in the 
coal, — that which is freest from sulphur will give a soot containing the 
least gypsum. The ammonia and the soluble substance containing ni- 
trogen will vary with the quantity of nitrogen contained in the coal and 
with certain other causes — so that the composition of different samples 
of soot may be very unlike, and their influence upon vegetation there- 
fore very unequal. The consequence of this must be, that the results 
obtained in one spot, or upon one crop, are not to be depended upon, as 
indicative of the precise effect which another specimen of soot will pro- 
duce in another locality, and upon another crop even of the same kind. 
And thus it happens that the use of soot is more general, and is attended 
with more beneficial effects, in some districts than in others. 

a. In general it may be assumed that where ammonia or its salts 
will benefit the crop, soot also will be of use, and hence its successful 
application to grass lands. From its containing gypsum it should also 
especially benefit the clover crops. Yet Dr. Anderson says, " 1 have 
used soot as a top-dressing for clover and rye-grass in all proportions, 
from one hundred bushels per acre to six hundred, and I cannot say that 
ever I could perceive the clover in the least degree more luxuriant than 
in the places where no soot had been applied. But upon rye-grass its 
effects are amazing, and increase in proportion to the quantity so far as 
my trials have gone."f And his general conclusion is, that soot does 
not affect the growth of clover in any way, while it wonderfully promotes 

* Annates de Chimie et de Physique, xxxi., p. 37. 
t Dr. Anderson's Essays (odit. 1800), ii.. p. 30i. 



ACTION OF SOOT UPOI* WHEAT A?(D OATS. 439 

that of rye-grass. Will any of you, by experiment, ascertain if such 
be really the case with the soot of your own neighbourhood ? 

h. The presence of ammonia in soot causes it, when laid in heaps, to 
destroy all the plants upon the spot ; and Dr. Anderson adds the inter- 
esting observation, " that the first plant which appears afterwards is 
constantly the common couch-grass {triticum repens).* 

c. This ammonia also causes soot to injure and diminish the crop in 
very dry seasons. Thus the produce of a crop of beans, after oats, in 
1842, upon an 

Unmanured part of the field was . . . 29^ bushels. 
Dressed with 4 bushels of soot .... 28 bushels. f 

It also diminished, in a small degree, the potatoe crop in the same 
year in the experiments of Lord Blantyre, at Erskine (Appendix, 
No. TX.)— 

With manure alone, the produce was .... 11 tons 17 cwt. 

With 30 bushels of soot sprinkled over the dung . 11 tons 4 cwt. 

Like rape-dust (p. 434) and saline substances, therefore, soot seems 
to require moist weather, or a naturally moist soil, to bring out all its 
virtues. 

d. Yet even in the dry season of 1842, its effect upon wheat and oats 
in the same locality (Erskine) was very beneficial. Thus the compara- 
tive produce of these crops, when undressed and when top-dressed with 
10 bushels of soot per acre, was as follows: — 

Unmanured "Wheat 44 . . . Oats 49. 

Top-dressed with soot . . . Wheat 54 . . . Oats 55. 
But the dressed wheat was inferior in quality to the undressed — the 
former weighing only 58, the latter 62 lbs. a bushel. In the oats there 
was no difference. Are we to infer from these results that, even in dry 
seasons, soot may be safely applied to crops of corn, while to pulse and 
roots it is sure to do no good ? Further precise observations, no doubt, 
are still necessary — and the more especially as the experiments upon 
oats and wheat, made in the still drier locality of Lennox Love (Appen- 
dix, No. VIII.), gave a decrease in the produce of grain — while in Mr. 
Fleming's experiments upon turnips (Appendix, No. VIII.), 50 bushels of 
soot, applied alone, gave an increase of 4 tons in the crop. 

e. An experiment of Lord Blantyre's (Appendix, No. IX.), enables us 
to judge of the efficacy of soot in a dry season, compared with that of 
nitrate of soda and of guano upon the produce of hay. Thus the crop 
of hay, per imperial acre, from the 

Undressed portion, weighed . 
Dressed with 40 bushels of soot 

160 lbs. nitrate of soda 

160 lbs guano . 

In this experiment the soot proved a more profitable application than 
either of the other manures. 

/. In regard to this substance, I shall only advert to one other obser- 
vation — but it is an important one — made by Mr. Morton, when des- 

• Dr. Andprson's Es'fcii/s(eA\t. 1800), ii., p. 305. i 

t See ApiifiKiix, No. \ ill. 

37* 



)ns. 

1 
1 
1 
2 


cwts. 

8 

15 

19 

2 


Cost. 
£ s. d. 


11 8 

1 15 9 
1 15 9 



440 USE OF CHARCOAL-DUST, AND OF COAL-TAR. 

cribing the management of a well conducted farm in Gloucestershire.* 
" The quantity of soot used upon this farm amounts to 3000 bushels 
a-year, one-half of which is applied to the potatoe, the other half to the 
wheat crop." All the straw grown upon this farm is sold for thatch, 
and for the last 30 years the only manure that has been purchased to 
replace this straw is the soot, which is brought from Gloucester, Bristol, f 
and Cheltenham. Soot no doubt contains many things useful to vege- 
tation, yet where all the produce is carried off, and soot only added in 
its stead — even the rich soils of the vale of Gloucester cannot be expected 
to retain a perpetual fertility. The slow changes which theory indi- 
cates may altogether escape the observation of the practical man, who 
makes no record of the history of his land, and yet may be ever slowly |j 
proceeding. 7 1 

2°. Charcoal. — "Wood -charcoal, from its porous nature, and its tend- 
ency to absorb animal odours and other unpleasant effluvia (Lee. I., § 2), 
has been found, when reduced to fine powder, to be an excellent admix- 
ture for night soil, for liquid manure, and for other substances which un- 
dergo putrescent decay. It is therefore employed to a considerable extent 
by the manufacturers of artificial manures. Jt is also applied with ad- 
vantage in some cases as a top-dressing to various cropsj — its efficacy 
being probably due in part to its power of absorbing from the air, or of re- 
taining in the soil, those gaseous substances which plants require, and in 
part to the slow decay which it is itself capable of undergoing. In moist 
charcoal powder seeds are said to germinate with great ease and cer- 
tainty. 

3"^. Coal-tar. — Another product of coal, the tar of the gas-works, has 
recently been recommended as an admixture for peat and similar com- 
posts, and it is one of the substances with which Mr. Daniel impreg- 
nates his saw-dust in the manufacture of his patent manure. It is im- 
possible to say how much of the good efTect derived from the use of 
such mixtures as that described in the Appendix, No. VIII., is due to the 
coal-tar they contain, — and as no experiments have hitherto been made 
from which the true action of coal-tar can be inferred, it may still be 
considered as a matter of doubt whether it can at all add directly to the 
fertility of the soil. 

§ 14. Of the theoretical value of different vegetable substances 

as manures. 

Vegetable manures are known to difler in fertilizing virtue. Thus, 1 
ton of rape-dust is said to be equal to 16 of sea-weed or to 20 of farm- 
yard manure. On what principles do these unlike fertilizing virtues 
depend ? 

i*^. According to Boussingault and other French authorities, the rela- 
tive efficacy of all manures depends upon the proportions of nitrogen they 
severally contain.^ And taking farm-yard manure — consisting of the 

* That of Mr. Dimmery, described in the Journal of the Royal Agricultural Society, I, 
p. 400. 

t At Bristol the price of soot is 9d. a bushel, at Gloucester only 6d., yet the former is pre- 
ferred even at the higher price. It is of better quality, owing, it is said, to the greater length 
of the chimnies — it may be also to the quality of the coal and to the way it is burned. 

J See Mr. Fleming's experiment upon Swedes (Appendix No. Vlll.), in which 50 bush- 
els of charcoal powder increased the crop by three tons an acre. 

§ Annales de Chtmie et de Phys., 3d series, III., p, 76. 



THEORETICAL VALUE OF VEGETABLE MANURES. 441 

mixed droppings and litter of cattle— as a standard, they arrange vege- 
table substances as manures in the following order of value : — 

Equal effects are produced by 

Farm-yard manure . .... 1000 lbs. 

Potatoe and turnip C?) tops 



Carrot tops 

Natural grass . 

Clover roots 

Fresh sea- weed 

Sea- weed dried in the air 



750 
470 
760 
250 
450 to 750 
300 



Pea straw 220 " 

Wheat straw 750 to 1700 '| 

Oat straw • 1400 |^ 

Barley straw ^i^O 

Rye straw 1000 to 2400 ''^ 

Buck-wheat straw ^^^ 

Wheat chaff ........ 470 " 

Fir saw-dust 1700 to 2500 " 

Oak do 750 ''^ 

Soot, from coal 300 

Lint and rape-dust 80 " 

The numbers in this table agree with the results of experiment in so 
far as they indicate that green substances generally, when ploughed in 
as manures, should enrich the soil more than an equal weight of farm- 
yard manure — that the roots of clover should be more enriching still — 
and that sea-weed is likewise a very valuable manure. They agree 
also with practical observation in placing pea, and probably bean straw, 
far above the straws of wheat, oats, &c., in fertilizing power, and in re- 
presenting soot and rape-dust as more powerful than any of the other 
substances in the table. So far, therefore, a certain general reliance 
may be placed upon the fertilizing value of a substance as represented 
by the proportion of nitrogen it contains. 

But if we bear in mind that plants, as we have frequently had occa- 
sion to mention, require inorganic as well as organic food, it is quite 
clear that the mere presence of nitrogen in a substance is not sufficient 
to render it highly nutritive to growing plants. Otherwise the salts of 
ammonia would be the richest manures of all, and would best iiourish 
and bring to perfection every crop and in all circumstances — which ex- 
perience has proved to be by no means the case. Hence 

2°. The value of vegetable substances as manures must dejjend in 
some degree upon the quantity and kind of inorganic matter they contain. 
In reference to the quantity of inorganic matter which they respectively 
impart to the soil, their relative values are represented by the following 
numbers ;•— 

One ton contains of inorganic 
matter about 

Potatoe tops, green 26 lbs. 

Turnip tops, do. ....... 48 '^ 

Carrot tops, do 45 " 

Rye-grass, _ do . 30 " 



442 INFLUENCE OF THE CARBONACEOUS MATTER. 

One ton contains of imrganic 
matter about 

Vetch, gi-een 38 ibs. 

Green sea- weed, do 22 " 

Hay . . . . ... . . 90 to 180 " 

Pea straw jqO k 

Bean straw ' 60* to 80 " 

Wheat straw . . . . . • . . 70 to 360 " 

Oat straw 100 to 180 " 

Barley straw 100 to 120 " 

Rye straw 50 to 70 " 

Fir saw-dust 6 " 

Oak saw-dust 5 " 

Soot [ [ 500 " 

Rape-dust 120 " 

This table places the several vegetable substances in an order of effi- 
cacy considerably different from the former, in which they are arranged 
according to the quantity of nitrogen they respectively contain. We 
?cnow that wood-ashes (p. 353), kelp, and the ashes of straw (p. 356), 
do promote the fertility of the land, and therefore the absolute as well 
as the relative efficacy of the above vegetable substances must depend 
in some degree upon the quantity of inorganic matter they contain. 
But we should be wrong were we to ascribe the total effect of any of 
them to the inorganic matter alone. 

3°. Even the carbonaceous matter of plants contributes its aid in in- 
creasing the produce of the soil by supplying, either directly or indirectly, a 
portion of the necessary food of plants. This has already been shewn 
in various parts of the preceding lectures. 

It is the property of substances which contain a larger proportion of 
nitrogen to undergo rapid decay in the presence of air and moisture, and 
thus to produce a more immediate and sensible action upon growing 
plants. But the carbon changes more slowly, and the inorganic mat- 
ter also separates slowly from decaying vegetables in the soil— and hence 
the apparent effects of these constituents are less striking. Thus the 
immediate and visible effect of different vegetable substances, in the same 
state, is measured by the relative quantities of nitrogen they contain — 
their permanent effects by the relative quantities of inorganic and of car- 
bonaceous matters. In the case of rape-dust for example, the inj mediate 
effect is determined chiefly by its nitrogen — the permanent effects, by 
the ash it leaves when burned, or when caused to undergo complete de- 
cay in the air. 



LECTURE XVIII. 

Animal manures.-Flesh, blood, and skin.-Wool woollen rags hair ^|o"^' ='"^.„^°"^^^^ 
what dops the fertilizing action of bones depend i— Animal charcoal 5"^^ /"e refuse o me 
Tgar refineries.-Fish and fish-refuse, whale blubber and ""-R^i^S'^ f^''^' "'';1!L\"^?[ 
the substances previously described-Pigeon dung. -Dung of sea-fowl: guano.-Liqu^^^ 
manures- the urine of various animals.— Mixed animal and vegetable manures. -Night 
Srt I dropping" of the horse, the cow, the pig.-Effects of digestion upon vegetable 
food.-Why equal weights of vegetable matter, and of the droppmgs of animals fed upo^ 
it, possess different fertilizing powers.-Farm-yard dung.- Weight of dung produced Irom 
a given weight ofgrass, straw, and other produce.— Loss undergone by farm-yard manure 
during fermentation.— Improvement of the soil by irrigation. 

Animal substances have always been considered as more fertilizing 
tot he land than such as are of vegetable origin. Their action is in 
general more immediate and apparent, and it takes place wuhin such a 
limited period of time that the farmer can calculate upon its being exer- 
cised in benefitting the crop to which it is applied. The reason of this 
more immediate action will presently appear. 

§ 1. Of fleshy Uood, and skin. 

1°. Flesh.— The flesh of animals is not only a rich manure in itself, 
but the rapidity with which it undergoes decay in our climate enables 
it speedily to bring other organic substances with which it maybe mixed 
into a state of active fermentation. It is only the flesh of such dead 
animals, however, as are unfit for food that can be economically ap- 
plied to the land as a manure. 

The flesh of animals consists o^nlean part, called the muscijlar hbre, 
or by chemists fibrin, and a fatty part, intermixed with the lean in greater 
or less proportion, according to the condition of the animal. Of these two 
it is the lean part which acts mo.st immediately and most energetically 
in the promotion of vegetation. Lean beef, in the recent state, contains 
77 per cent, of its weight of water, so that 100 lbs. consists of 77 lbs. of 
water and 23 lbs. of dry animal matter. 

2°. Blood.— The blood of animals is more extensively employed as 
a manure. It is carried off in large quantities from the slaughter-houses 
of the butchers, and makes rich and fertilizing composts. In some 
parts of Europe it is dried, and in the state of dry powder is applied 
with much effect as a top-dressing to many crops. 

Liquid blood consists of fibrin— the substance of lean meat, of albu- 
men—the same as the white of eggs— of a red colouring niatter, and of 
certain saline substances dissolvedin a considerable quantity of water. 
When blood cools it gradually congeals, and separates into two parts, 
a gelatinous red portion, called the dot, and a liquid, nearly colourless, 
part, called the serum. The clot contains most of the fibrin and colour- 
ing matter, and a portion of the albumen; the serum, the greater part 
of the albumen and of the soluble sahne substances which are present 

in the blood. , ^ t -j , , » 

The relative composition of fresh muscular fibre and of liquid blood 

is thus represented in 100 parts : — 



5183 


51-96 


757 


7-25 


1501 


15-07 


21-37 


21-30 


4-23 


4-42 



444 COMPOSITION or blood, and or skin. 

Water. Dry animal matter. 

Muscular fibre, 77 23 

Blood 79 21* 

It appears singular that the solid muscle of animals should contain 
so nearly the same quantity of water as their liquid hlood does. 

But it is no less striking that the dry animal matter which remains,when 
lean muscular fibre and when blood are fully dried, has nearly the same 
apparent composition. Thus, according to the analyses of Playfair and 
Boeckman, dry flesh and dry blood consist respectively of — 

Dry beef. Dry ox blood. 
Carbon, ....... 

Hydrogen, 

Nitrogen, 

Oxygen, 

Ashes, 

100 loot 

The organic part, therefore, of blood and of flesh is nearly identical in 
ultimate composition, and the final result of equal weights of each, m 
when applied as manures, should be nearly the same. The ashes, how- Ij 
ever, or inorganic part, though present in each nearly in the same pro- 
portion (4'23 and 4*42 per cent.), are somewhat different in composition, 
and therefore the action of blood and flesh will be a little unlike in so 
far as it depends upon the saline substances they are respectively capa- ^ , 
ble of conveying to the roots of plants. 1 

3°. Skin. — The skins of nearly all animals find their way ultimately 
into the soil as manure, in a more or less changed state. 

The refuse parings from the tan-yards, and from the curriers' shops, 
though usually employed for the manufacture of glue, are sometimes 
used as a manure, and with great advantage. They may either be 
])loughed in sufficiently deep to prevent the escape of volatile matter 
when they begin to decay, or they maybe made into a compost by which 
their entire virtues will be more effectually retained. 

Skin differs considerably in its constitution from flesh and blood. It 
contains, in the recent state, about 58 per cent, of water, and leaves, 
when burned, only 1 per cent, of ash. The combustible or organic part 
consists of — 

Carbon 50-99 

Hydrogen 7*07 

Nitrogen 18-72 

Oxygen 23-22 

100 
It contains, therefore, 3^ per cent, more nitrogen than flesh or blood. 
So far as the fertilizing action of these substances depends upon the 
proportion of this constituent — glue, the parings of skins, and all gelati- 
nous substances will consequently exhibit a greater efficacy than flesh 
or blood. 

* Thomson's Animal Chemistry, pp. 285 and 367. 

t Liebig's Organic Chemistry ajipUed to Physiology, p. 314. 



USE AND COMPOSITION OF WOOL, HAIR, AND HORN. 445 

§ 2. Wool, woollen rags, hair, horn, and bones. 

1°. Wool, in the form of the waste of the spinning-mills, and espe- 
cially in that of woollen rags, acts very efficaciously as a manure. The 
I rags are used with good effect upon light chalks and gravels, in which 
they retain the water. They are sometimes ploughed in for wheat along 
i with the clover stubble, in the winter with the corn stubble, when the 
land is intended for turnips, and are sometimes applied as a top-dressing 
to clover and grass lands.* They are used most extensively, however, 
in the hop-grounds, being dug in round the roots, to which they continue 
for a long time to supply much nourishment. The estimation in which 
they are^ held may be judged of by the price they bring, which is from 
£5. to c£lO. a ton. 

2°. Hair also is fitted to produce effects similar to those which follow 
the use of wool. It can seldom, however, be obtained by the farmer at 
so economical a rate as to enable him to trust to it as an available re- 
source when other manures become scarce. 

3°. Horn, in the form of horn shavings, parings, and turnings, is just- 
ly considered as a very powerful manure. Even in the state of shav- 
ings, however, it undergoes decay still more slowly than woollen rags; 
an^, therefore, like them, will always be most safely and economically 
employed when previously rotted, by being made into a compost. 

Wool, hair, and horn, differ from flesh, blood, and skin, by containing 
very much less water in their natural state, and by undergoing, in con- 
sequence, a much slower decay, and exhibiting a much less immediate 
action upon any crop to which they may be applied. The intelligent 
farmer, therefore, will bear this important distinction in mind, in any 
opinion he may form as to the relative efficacy of these several sub- 
stances as general fertilizers of the land. 

In chemical composition, these three substances are nearly identical, 
and they do not differ widely from the lean of beef or from dried blood. 
When burned they leave only a small quantity of ash : — 

Wool leaves . . . . . 2-0 per cent, of ash. 

Hair 0-72 " ♦' 

Horn 0-7 " " 

And the part which burns away — the organic part — consists of— -i 

Wool, Hair, Horn. 

Carbon ...... 5065 5153 51-99 

Hydrogen .... 703 669 6-72 

Nitrogen 1771 1794 1728 

Oxygen and Sulphur , . 24 Gl 2384 2401 

100 100 100 

The organic part of these three substances, therefore, is nearly iden- 
tical in composition, and hence, when equally decomposed they ought 
to produce the same effects upon the young crops. They contain a lit- 
tle more nitrogen than dried flesh and blood, and a little less than dried 
skin, and therefore in so far as their fertilizing action depends upon this 
element, they ought to occupy an intermediate place between these se« 
veral substances. 

^ British HusbandTy, I., p. 425. 



- "yaigj^;,.^ ^^**!^" -■ 



446 THE INORGANIC MATTER COIfTA!NEI) IN ^OiiZS. 

§ 3. Of the composition of bones. 

Few substances have of late years done so much to increase the agri- 
cultural produce of various parts of England as the use of crushed boneaj 
for manuring the land. 

1°. Recent bones contain a variable quantity of water and fat. Ther] 
proportion of fat depends upon the position of the bone in the body, andf 
upon the condition of the animal. The proportion of water dependsj 
partly upon the solidity of the bone and partly upon its age. Accord- 
ing to Denis, the radius of a female, 

Aged 3 years, contained . . 33-3 per cent, water, with a little fat. 

Aged 20 years, " . . 13-0 " » 

Aged 78 years, " . . 15-4 " " 

The quantity of water thus present in bones performs an important 
part in determining the action which bone-dust is known to exercise 
upon the land. The oil is sometimes extracted by boiling the bones. 
During this boiling they absorb more water, and thus, when laid upon 
the land, undergo a more rapid decomposition, and exercise, in conse- 
quence, a more immediate and apparent, and therefore, as some may 
think, a more powerful fertilizing action. 

2°. But bones differ from the other animal substances already de- 
scribed chiefly by containing a much larger proportion of inorganic mat- 
ter, or by leaving, when burned, a greater per-centage of ash. The 
quantity of inorganic matter, however, contained in bones is not con- 
stant. It is less in the young than in the full-grown animal — less in the 
spongy than in the compact or more solid bones — and less in those of 
some" animals than in those >of others. Thus, when freed from fat and 

perfectly dried — 

Of inorganic matter. 
The lower jaw-bone of an adult " left 68'0 per cent. 

_ „ a child of 3 years —62-8 « 

A compact human bone , , . . — 587 " 
A spongy human bone .... — 50*2 " 

, The tibia of a sheep —4803 " 

The vertebrje of a haddock ... — 60-51 " 

It is obvious that the relative efficacy of equal weights of bones must 
be affected by such differences in the relative productions of organic and 
inorganic matter which they severally contain. 

3°. This inorganic matter or ash consists in great part of phosphate of 
lime (Lee. IX.,"§ 4), but it contains also a considerable though variable 
proportion of carbonate of lime, with smaller quantities of several other 
ingredients. The proportion of carbonate of lime appears to be smallest 
in carnivorous animals. 

Thus, for every 100 parts of phosphate of lime there exists in — 
Human bones about .... 20-7 carbonate of lime. 



Bones of the sheep 
Do. ox 



Do. fowl . . 

Do. haddock 

Do. frog . 

Do. lion . 



24-1 

13-5 

11-7 

6-2 

5.8 

2-6 



COMPOSITION OF BURNED BONES* 447 

These proportions are not to be considered as constant, because it varies 
not only in ihe different bones of the same animal but also in bones from 
the same part of the body of different animals of the same species.* 
But the existence of such differences must render unlike the fertilizing 
action of the bones of different animals — if, as many think, this action 
depends in any great degree upon thequantity of phosphate of lime which 
they respectively contain. 

4°. Besides the phosphate and carbonate of lime, I have stated that 
bones contain certain other inorganic substances, which are found in 
small quantity in the ash. What these substances are will appear in 
the following table, which represents the constitution of the bones of 
some animals, as analysed by Dr. Thomson : 

Ileum 
of a sheep. 
Organic or combustible matter . 433 
Phosphate of lime . . . 50-6 

Carbonate of lime . . . 4"5 

Magnesia 0-9 

Soda 0-3 

Potash .0-2 



Ileum 


Vertcbrse 


of an ox. 


of a haddock. 


48-5 


39-5 


45-2 


561 


61 


3-6 


02 


0-8 


0-2 


0-8 


01 


— 



99-8 100-3 100-8 

The soda exists in bones probably in the state of common salt, and 
the magnesia in that of phosphate. An appreciable quantity of fluoride 
of calcium, with traces of iron and magnesia, are also generally found 
in bones, in addition to the substances indicated in the preceding 
analyses. 

5°. When bones are heated to redness in the open air the organic 
part burns away, and leaVes the white earthy matter in the form, and 
nearly of the bulk, of the original bone. But if a dry bone be covered 
with dilute muriatic acid, the earthy or inorganic part is slowh' dis- 
solved out, and the organic part — the cartilage or gelatine — will alone 
remain, retaining also the form and size of the organic bone. In this 
state it is flexible and somewhat soft, and by prolonged boiling may be 
dissolved in water, and manufactured into glue. 

This organic or combustible part of bones is identical in chemical 
composition with skin and glue, and is nearly the same as wool, hair, 
and horn, of which the analysis has already been given. In so far, 
therefore, as their efficacy depends upon the organic constituent, dry 
bones must be greatly inferior to an equal weight of any of ihe other 
animal substances above described, because of the much greater pro- 
portion of earthy matter they contain. 

§ 4. On ivhat does the fertilizing action of hones depend? 

Bones contain, as we have seen, a large proportion both of organic 
and of inorganic matter; — on which of these two constituents does their 
fertilizing action most depend ? Some regard the phosphate of liine or 
bone earth, as the only source of the benefits so extensively derived from, 
them — and it is by supposing the soil to be already sufficiently impreg- 
nated with this phosphate that Sprengel accounts for the little success 

• Thomson's Animal Chemistry^ p. 242. 
38 



448 EFfECT OF BOILING UPON fiONES. 

which has attended the use of bones in Mecklenburg and North Ger- 
many. Others, again, attribute the whole of their influence to the or- 
ganic part — the gelatine — which bones contain. Neiiherof these views 
is strictly correct. Plants, as we have seen, require a certain f|nantiiy 
of phosphoric acid, lime, and magnesia, which are jjresent in ilie inor- 
ganic part of bones ; and so far, therefore, are capable of deriving inor- 
ganic iood from bone-dust. But the organic part of bones will decom- 
pose, and therefore will act nearly in the same way as skin, wool, hair, 
and horn do — which substances it resembles in ultimate composition.* 
It cannot be doul)ted, therefore, that a considerable part of the etfect of 
bones upon all crops must be due to the gelatine which they contain. 

The principal facts, now known in regard to the action of bones, may 
be thus stated : — 

1°. The organic matter of bones acts like that of skin, woollen rags, 
horn shavings, &c., but as bone-dust contains only about one third of 
the organic matter which is present in an equal weight of either of the 
above substances, its total effect, in solar as it depends upon the organic 
matter, will be less in an equal proportion. 

2°. But as the organic matter of bones contains more water than 
horn or wool,f it will decay more rapidly than these substances when 
mixed with the soil, and will therefore be more immediate in its action. 
Hence, the reason why woollen rags and horn shavings must be ]>k)ughed 
in in the preceding winter, if they are to benefit the subsequent wheat or 
turnip crops, while bone-dust can be beneficially applied at the sowing 
of the seed. 

3°. When bones are boiled the oil will be separated, and a portion of 
the gelatine will at the same time be dissolved out.J The bones, there- 
fore, will be in reality rendered less rich as a manure. But as they at 
the same time take up a considerable quantity of water, boiled bones 
will decompose more rapidly when mixed with the soil, and thus will 
appear to act as beneficially as unboiled bones. Hence the reason why 
in Cheshire, where boiled bones are used to a considerable extent, many 
practical men are of opinion that their action upon the crops is not infe- 
rior to that of bones from which the oil 1ms not been extracted by boiling. 
The immediate effect may indeed be e(]ual, or even greater, than that 
of unboiled bones, but the total effect must be less in proportion to 
the quantity of organic matter which has been removed by boiling. 
Cases, however, may occur in which the skilful man will prefer to use 

* The main (Inference is in the quantity of sulphur containefl in hair. An analysis of hu- 
man liair, by Van Laer {AnnaJen der Pharmur.ie, xlv.. p. 168), wfiich has reached me since 
the precetlinp slicet went to press, sliows Ihe proportion of sulphur more accurately liian 
that wliich is given at page 445. He founrl human hair of various colours to leave 
from oneliuni to nearly (wo per cent, of ash when burned, and to consist besifies of Carbon, 
50 65— Hydrogen, 6 36— Nitrogen, 17 14— Oxygen, 20 85— Sulphur, 500— Total, 100— and 
nearly half a per cent, of Phosphorus. 

t Above, p. 446. 

X The prolonged boiling of bones, so as to dissolve a portion of the gelatine, is practised to 
a considerable extent as a mode of manufacturing size or glue. In the large dyeinsr establish- 
ments in Manchester, the bones are tioiled in open pans (or 24 hours. Ihe fat skimmed off 
and sold to ilic candle-makers, and (he size afterwards boiled down in another vessel till it 
is of sufficient strength for stifTeuing the thick goods for which it is intended. The size 
liquor, wlien exhausted, or no longer of sufficient strength for sliffening, is applied with 
much benefit as a manure to the adjacent i)asiure and artificial grass lands, and the bones 
are readily bought up by the Lancashire and Chesliire farmers. The boiled bones must, 
evidently lose all the fertilizing virtue which the size liquor acquires. 



COMPOSITION OF LONG-BURIED BONES. 449 

boiled bones because ihey are fitted to produce more immediate effect 
where — as in the pushing forward of the young turnip plant — such an 
effect is particularly required. 

4°. When bones are buried in a more or less entire state, as they oc- 
casionally are about the roots of vines and fruit trees, they gradually 
decay, and sensibly promote the growth of the trees to which they are 
applied. Yet after the lapse of years these same bones may be dug up 
nearly unaltered either in form or in size. The bonesof a bear and of a 
stag, after being long buried, were found by Marchand to consist of — 

Bones of the bear buried 





deep. 


Animal matter 


16-2 


Phosphate of lime . 


560 


Carbonate of lime . 


131 


Sulphate of lime 


71 


Phosphate of magnesia . 


0-3 


Fluoride of calcium 


20 


Oxide of iron and manganese 


20 


Soda 


11 


Silica 


2-2 



shallow. 


Femur of a stag. 


4-2 


73 


621 


541 


133 


19-3 


123 


122 


0-5 


21 


21 


21 


21 


2-9 


13 


— 


21 


— 



100 100 100 

The most striking change undergone by these bones was the large 
loss of organic or animal matter they had suffered. The relative pro- 
portions of the phosphate and carbonate of lime had been comparative- 
ly little altered. The main effect, therefore, produced by bones when 
buried at the roots of trees, and their jirst effect in all cases, must be 
owing to the animal matter they contain — the elements of this animal 
matter, as it decomposes, being absorbed by the roots with which the 
bones are in contact. 

Such facts as this prove, I think, the incorrectness of the one-sided 
opinion too hastily advanced by Sprengel, and after him reiterated by 
Liebig and his followers — that' the principal efficacy of bones is, in all 
cases, to be ascribed to their earthy ingredients, and especially to the 
phosphate of lime. 

This opinion of Sprengel rests mainly on two facts put forward by 
himself.* Bones, he says, have failed to produce in North-Western 
Germany the good effects for which they are so noted in England, yet 
in the same districts, farm-yard and other animal manures exhibit their 
usual fertilizing action. It cannot, therefore, he concludes, be tlie ani- 
mal matter of bones to which their beneficial influence is to be ascribed. 
But to this conclusion we may fairly demur, when we know how often 
on heavy and undrained lands bone-dust fails even among ourselves. 
Let bones be tried for the turnip crop — a crop still almost unknown in 
Northern Germany — and upon well drained .soils similar to those of our 
best turnip lands, and I venture to predict, in opposition to Sprengel's 
experience, that bones will no longer fail even in Mecklenburg. 

Again, having drawn his conclusion in regard to the inutility of the 
animal matter, Sprengel states that the marl which is applied to the 
land in Holstein and the neighbouring provinces, contains phosphate of 
lime (p. 371), and hence the "reason why the earthy matter of the boues 

* Lehre vom Dutiger, p. 153. 



450 CAUSE OF THE PROLONGED EFFECT OF BONES. 

applied does not improve the land. In so far as the efficacy of bones 
really depends upon their earthy constituents, the use of a marl con- 
tainino; phosphate of lime* will, no doubt, greatly supersede them ; — but 
in so far as it depends upon the animal matter they contain, bones will 
exhibit their natural fertilizing action, however rich the soil may al- 
ready be in those compounds of which their earthy or incombustible 
part consists. 

5°. Yet there is reason to believe — nay, it may be assumed as cer- 
tain — that the phosphate and carbonate of lime which' bones contain so 
largely, are not without effect in promoting vegetation. All our culti- 
vated plants recpiire and contain both phosphoric acid and lime,f and 
from the vegetables on which they feed, all animals derive the entire 
substance of their bones. This same phosphoric acid and lime, there- 
fore, must exist in the soil on which the plants grow, or they will nei- 
ther thrive themselves nor be able properly to nourish the animals they 
are destined to feed. If a soil, then, be deficient in phosphate of lime or 
its constituents, it is clear that the addition of bones will benefit the after- 
crops not only by the animal but by the earthy matter also which they 
contain. And that such is the case, in many instances, there is good 
reason for believing. But that this can by no means account for the 
whole effect of bones, even supposing the soil to which they are applied 
to be, in every instance, deficient in phosphates, is clear from the fact 
(see Lee. X., § 4), that 260 lbs. — less than 6 bushels — of bone-dust per 
acre are sufficient to supply all the phosphates contained in the crops which 
are reaped during an entire fourshift rotation of turnips, barley, clover, 
and wheat. Yet the quantity of bones actually applied to the land is 
from three to five times the above weight, repeated every time the tur- 
nip crop comes round. 

6°' Still, granting that the chief effect of bones upon the immediately 
succeeding crops is due to their organic part, upon what does their 
jyrolongcd ^{ood effect depend ? Some lands remember a single dressing 
of bones for 16 or 20 years, and some after the application of 2 or 2i 
tons of bones have yielded 10 to 15 successive crops of oats, and have 
been sensibly benefitted for as many as siivty years after the bones were 
ai)])lied.t 

This prolonged effect is also due in part to both constituents. When 
not crushed to powder, the organic matter of bones is always slow in 
disappearing, and slower the deeper they are buried. In some soils, 
also, the process is more slow than in others. The long-buried bones of 
the bear and of the stag, of which the analysis is given above (p. 419), 
had lain in the soil for an unknown period, and yet they still contained 
a sensible proportion of animal matter. So it is with the bones used for 
manure, when they are not crushed too fine. They long retain a por- 
tion of their organic matter, which they give out more slowly, and 
in smaller quantity, every year that passes, yet still in such abun- 
dance as to contribute sensibly to the nourishment, and in some de- 

* Most lime-stones and shell-sands contain an appreciable quantity of this phosphate, and 
will, Uiercfore, to the same extent, supersede the use of the earthy matter of bones. Much 
of the marl of Holstein consists of the detritus of chalk rockg, anciently broken up and car- 
ried off— by the waters of tlie sea with which that part of Europe was covered at no very 
remote jreoloiiical epoch. 

+ See Lee. X., §3. 

X See Appendix, No. I., and British Husbandry^ I., p. 398. 



♦ 



FERTILITY OF ANCIENT BATTLE-FIELDS. 451 

gree to promote the growth, of the crops which the land is made 
to bear.* So it would be wiih the horns and hoofsof cattle, if laid on in 
equal quantity, for they also decay with exceeding slowness, 

Still the inorganic part is not without its use. If the soil be deficient in 
phosphates or in lime, the earthy matter of the bones will supply these 
substances. I only wish to guard you against the conclusion, that be- 
cause bones often act for so long a period, that therefore theorganic mat- 
ter can have no share in the influence they exercise after a limited period 
of years. 

He who candidly weighs the considerations above presented will, I 
think, conclude that the whole effect of bones cannot in any case be 
ascribed exclusively eitlier to the one or to the other of their principal 
constituents. He will believe, indeed, that in the turnip husbandry the 
organic part performs the most prominent and most immediately useful 
office, but that the earthy part, nevertheless, affords a ready supply of 
certain inorganic kinds of food, which in many soils the plants would 
not otherwise easily obtain. He will assign to each constituent its sepa- 
rate and important function, being constrained, at the same time, tocon- 
fess that while in very many cases the earthy part of bones, applied 
alone, would fail to benefit the land, there are few cultivated fields in 
which the organic part applied alone would not materially promote the 
growth of most of our artificial crops. 

§ 5. Of the application of bone-dust to p)o.sture lands. 

Tf the soil be deficient in phosphate of lime, bone-earth alone, or the 
mineral phosphate (Lee. IX., § 4), may be advantageously applied to 
increase its fertility. In a four-years' rotation of turnips, barley, clover, 
and wheat, if bones be used for the turnip crop, the land will every ro- 
tation become richer in bone-earth, f and therefore the application of 
earthy phosphates cannot — after a few rotations — be expected materially 
to affect its productiveness. But pasture lands are treated differently, 
and it is not unlikely that in some instances the earth of bones, even ap- 
plied alone, may to such lands be productive of considerable benefit. 

The application of bone-dust to permanent pasture has of late years 
been practised with great success in Cheshire. Laid on at the rate of 
30 to 35 cwt., or at a cost of c£lO per acre, it has increased the value of 
old pastures from 10s. or 15s. to 30s. or 40s. per acre : and after a lapse 
of 20 years, though sensibly becoming less valuable, land has remained 
still worth ivSh or three times the rent it paid before the bones were 
laid on. 

It is this lengthened good effect of bone-dust that affords the strongesi 
ground for believing that the earthy phospbate has a large share in the 
effect. I have already shown that this prolonged action is not conclu- 
give upon the point — psince the organic matter lingers long, even in buried 

• This opinion derives a singularly interesting confirmation from the fact that a portion of 
the soil of an ai'able district in Sweden, "which from time immemorial had grown excellent 
-wheat without manure," was found by Berzelius to contain minute fragments of bone caipjh- 
ble upon boiling with water of yielding a weak solution of gelatine. It was concluded, 
therefore, that the spot had been an ancient battlefield, and that Us prolonged feriiliiy was 
due to the bones of old time buried in it, and still to some extent undecomposed (Marcliand). 

t See preceding page. 

38* 



♦ 



452 PHOSPHATE OF LIME YEARLY CARRIED OFF- 

bones — but a consideration of the necessary effect of long continuec 
pasturage upon soils to which nothing is artificially added, lends a sin- 
gular support to the view that the bone-earth may act an important and- 
beneficial part upon old meadow and other grass lands. Take the in-I 
stance of a dairy farm in the neighbourhood of a large town, — 

1°. The milk is all carried off" the farm, either directly or in the shape 
of butter, cheese, &c., and every 40 gallons of milk contain 1 lb. of 
bone-earth, besides other phosphates. Estimate the average yield of a 
good cow at 3000 quarts, or 750 gallons a-year, its milk will contain 19 
lbs. of earthy phosphate — as much as is present in 30 lbs. of bone-dust. 

2°. Again, the urine of a milk cow, taken at 700 gallons a-year, con 
tains about 11 lbs. of the same phosphate.* Suppose only a third of 
this to run fo waste, and the farm will lose for every cow in this way 
about 4 lbs. — equal to about 6 lbs. of bone-dust. 

S*^. But for every cow an annual calf is reared and sold off. Let this 
calf contain but 20 lbs. of bone — then Jbr every cow it maintains, a dairy 
farm will lose of earthy phosphates ujJon the whole as much as is contained 
in 56 lbs. of hone-dust. Suppose a farm to be pastured for centuries, as 
those of Cheshire have been, and the produce to be carried off' in the 
form of milk, butter, and veal — we may reasonably suppose that it will 
at length begin to feel the want of those phosphates which year by year 
have been drawn from its surface. It is reasonable also to suppose that 
the addition of these deficient phosphates would impart new vigour to 
the soil, would cause new grasses to sprout, and a more milk-yielding 
herbage to spring up. 

Such is the reasoning upon which I some years ago attempted to 
found an explanation of the singularly striking effects produced by bone- 
dust on the grass lands of Cheshire, while it failed materially to im- 
prove those of other districts on which it had been tried. I still consider 
it as by no means without its weight, though I cannot concur with the 
extreme views which some have since adopted — that either in the case 
of Cheshire, or in any other case with which I am acquainted, the benefi- 
cial action of bone-dust is to be ascribed solely to its earthy constituents. 

§ 6. Of animal charcoal^ the refuse of the sugar refineries^ and 
animalized carbon. 

1°. Animal charcoal {bone black). — When bones are charred or dis- 
tilled at a red heat in close vessels, they leave behind a coaly residuum 
to which the name of animal charcoal is usually given. By this calci- 
nation the animal matter is almost entirely decomposed. The charcoal 
still retains, however, a little nitrogen, and though it is seldom employed 
as a manure, yet it is not wholly without effect in promoting the growth 
of our cultivated crops. Thus in 1842, when applied to Swedish ■ 
turnips, Mr. Fleming obtained from the unmnnured soil 12 tons 5 cwt. 
per acre ; but when manured with 10 cwt. of animal charcoal, 21 tons 
2 cwt.f 

2°. Refuse charcoal of the sugar refiners. — The animal charcoal above 
described is chiefly employed for the purpose of removing the colour 

' A cow, not in milk, gives oo an average about 1300 gallons of urine (see page 460). 
t See Appentlii, No. VIU, 



REFUSE CHARCOAL OF THE SUGAR- REFINERS. 453 

from solutions of raw sugar. Blood is also used for clarifying the same 
solutions, and quick-lime for neutralizing the acid matter they contain 
— thus rendering the syrups more capable of easy crystallization. 
Hence the animal charcoal, the blood, the lime, and the colouring and 
other matters separated from the sugar, become mixed together, and 
form the refuse of the sugar refiners. This refuse often contains from 
one-fifth to one-fourth of its weight of blood, and hence is in general — 
and especially in France, where it is extensively employed as a manure 
— considered from four to six times more powerful than the pnre ani- 
mal charcoal alone. In the western parts of France this mixture has 
for some years been in great repute among agriculturists, and, in addi- 
tion to that which is produced at home, has been largely imported from 
other countries. Into the ports upon the river Loire alone there were 
entered, in 1839, upwards of ten thousand tons.* It sells at about tiv© 
pounds a ton. 

The value of this substance depends very much upon the proportion 
of blood which it contains, and as this is in some measure variable, its 
fertilizing qualities must be variable also. In England blood is used 
much more sparingly in the refining of sugar than it used to be, and 
hence the refuse of our refineries is probably less valuable as a manure 
now than it was in former years. f This is probably one reason why 
Mr. Fleming obtained from the use of it a somewhat smaller crop of tur- 
nips than from an equal quantity of the unused animal charcoal. Upon 
Swedish turnips 10 cwt. of unused animal charcoal gave him 21 tons 2 
cwt. ; while 10 cwt. of the refuse gave 10 tons 7 cwt.t 

Still this result is sufficiently favourable to recommend the refuse or 
exhausted animal charcoal to the practical agriculturist where more eco- 
nomical manures cannot readily be obtained. 

3"^. Animalized carbon. — The estimation in which the refuse charcoal 
of the sugar works was held, has led to the manufacture of very useful 
imitations of it under the name of animalized carbon. A calcareous 
soil, rich in vegetable matter, || is charred in close vessels, and is then mixed 
at intervals with repeated portions of night soil as long as it disinfects it 
or removes its smell — and to this mixture is added 4 or 5 per cent, of 
clotted and partially dried blood. This animalized carbon is said to bo 
of much value as a manure. The main objections to it are its liability 
to adulteration and the uncertainty to which, even when skilfully and 
conscientiously prepared, its composition must be in some measure liable. 

§ 7. Of fish, fish refuse, whale hluhber, and oil. 

1°. Fish. — In some parts of the world, and occasionally on the shores 
of England, fish are met with in such abundance that they can be econo- 
mically employed as a manure for the land. They are either spread over 

• Boussingault, An. de Chim. et de Phys., 3d series, iii., p. 96. 

t The refining " consists in putting (he sugar into a large square copper cistern along with 
some lime water, a little bullock's blood, and from 5 to 20 per cent, of bone black, and in- 
jecting steam througfi the mixture. Instead of the blood many refiners employ a mixture of 
gelatinous alumina and gypsum, called Jinings, prepared by adding lime water to a solution 
of alum, and collecting the precipitate" (Ure). Hence the reason why, in England at least^ 
the refuse charcoal of the sugar works is not always rich in blood. 

t Appendix, No. VIII. 

I An intimate mixture of peat and marl or shell-sand would answer well. 



454 OF FISH, FISH REFUSE, AND OIL ; AND THE RELATIVE 

it in a recent slate, or — which is more economical — are made into a com- 
post chiefly with earth, which afrer a time proves rich and fertilizing. 

The bones offish are similar in composition to thuS6 of terrestrial an- 
imals (p. 447), and their muscular parts are nearly identical in elenientary 
constitution with the lean part of beef and the clot of blood. As fertil- 
izing agents, therefore the parts of fishes will act nearly in the same 
way as the blood and bodies of animals. 

2°. Fish refuse. — The pilchards of Cornwall and the herrings, cod, 
and Ung of our Northern coasts, when cleaned for salting, yield'a large 
quantity of refuse,* which is peculiarly valuable to the'farmers in the 
neighbourhood of the principal fishing stations. 

in the North, a compost prepared from this fish refuse, is generally 
esteemed as a manure for barley and green crops, but when extensively 
used, "is said to render the soil unfit for the production of oats." Such 
soil is said to be poisoned. f 

3°. IVhale hlubler. — When the soil is expressed from whale blub- 
ber, a skinny or membraneous refuse remains, which has hitherto been 
employed only as a manure. It is made into a compost with earth, 
which is several times turned, and the mixture is most usefully em-Ij 
ployed after it has lain not less than 9 or 12 months. It may be applicdf' 
either to grass or to arable land. 

4°. Whale oil, and that of other fish, when made into a compost with 
earth and a little lime or wood ashes, yields a manure wliich was much 
recommended by the late Dr. Hunter of York.J Merely mixed wiih 
absorbent earth, and applied at the end of one month, impure whale 
oil, at the rate of 40 gallons per acre, gave the late Mr. Mason, of 
Chilton, near Durham, a crop of 23^ tons of turnips, while 40 bushels 
of bones gave him only 22 tons. More recently, also, it has been found 
that the mixture of a few gallons of oil with the usual quantity of bone- 
dust increased to a considerable degree the turnip croj) to which it was 
applied. In a theoretical point of view, it would be interesting to es- 
tablish the fact, that pure oil is capable of promoting in a large'degree 
the growth and produce of our cultivated crops— though, as a "resource, 
of which farmers in general can avail themselves where other manure 
is scarce, its high price will probably prevent it from ever becoming ex- 
tensively useful. 

§ 8. .Relative fertilizing value of tlie animal manures already 

described. 

No sufficiently decisive experiments are yet upon record, from which 
the relative value of the several animal nianures above described can 
be satisfactorily deduced. That they differ in fertilizing power every 
farmer is aware, but it is not yet decided by actual trial, in what pro- 
portion one of them exceeds the other. 

1 have already stated to you (p. 440) the theoretical opinion enter- 
tained by many, that the ejficacy of all manures is in proportion to the 
quantity of nitrogen they contain. Adopting this principle as true, it is 

* Fouileen barrels of herrings yield one of refuse. 

t Sinclair's Statistical Account of Scotland, vii., p. 201, quoted in British Husbandry, I., 
p. 421. 
X See his Georgical Essays, vols. 1, 2, and 5. 



FERTILIZING VALUE OF VARIOUS ANIMAL MANURES. 455 

«asy to assign to each substance its proper place in an artificial table. 
The last column in the following table shows the quantity of each sub- 
stance in its ordinary slate of dryness, which will be necessary to pro- 
duce the same effect as 100 lbs. of common farm-yard manure, sup- 
posing this effect to be determined by the nitrogen alone. 

Equal effects 
Water per cent. Ash per cent. Nitrogen per cent, produced by 
Farm-yard manure .80 '? k 100 lbs. 

Flesh ... 77 1 3i 14 

Fish ... 80 2 2a 20 " 

Blood ... 79 to 83 1 3 16 " 

Blood dried* . . 12 to 20 3^ 12 to 13 8 

Skin .... 58 * 8 12 " 

Wool, hair, and horn 9 to 11 1 to 2 16 6 ' 

Bones . . . 14 40 to 60 5 to 9 H to 20 " 

Refuse charcoal of the 

Sugar works .48 1 1 ? u 

Animalized carbon .45 1 1 •'" 

I have already had occasion to remark, however, that this mode of 
classifying manures is not altogether to be depended upon. Since — 

1°. "It does not lake into account the quantity of inorganic matter they 
severally contain, which as shewn in the third column is particularly 
large in bones, and is by some considered as the (most?) important and 
influential constituent of this manure. Nor is any effect ascribed to 
such substances as the sulphur, which in hair and wool forms nearly 5 
per cent, of their whole weight, and which cannot be wholly without 
influence upon the plants, by which, as they decay, the elements of 
these manures may happen to be absorbed. 

2°. It passes by the practical influence of the quantity of water which 
the several substances contain. Flesh, fish, blood, and skin, in their 
recent state, contain so much water that they begin almost immediately 
to decompose, and thus expend most of their fertilizing virtue upon the 
first crop to which they are applied. Hair and wool, on the other hand, 
retain so little water that they decay with great slowness. Hence, the 
true amount of the action of these latter substances cannot be estimated 
in a single year, and must therefore be altogether a matter of theory 
until a series of careful observations, made in consecutive years, shall 
afford some decisive facts upon which to reason. 

3°. This is confirpned by the statement of Boussingault and Payen,t 
that the effect of the animal charcoal of the sugar refiners and of the 
animalized carbon i§, hy experience, five times greater than the propor- 
tion of nitrogen they contain would indicate; and — 

4°. If pure oil, which contains no nitrogen at all, will yet produce an 
enriching manure by mere mixture with the soil (p. 454), or will in- 
crease greatly the effect of bones — we must obviously seek for some 
other principle upon which to account for the effect of manures, besides 
or in addition to the proportion of nitrogen they contain. It is true that 
the impure or refuse whale oil used for composts may contain some ni- 
trogen, but we can scarcely suppose 250 or 300 lbs. of such oil to hold 

* As it is sold for manure af. Paris and elsewhere, p. 443. 
t Annales de Chim. etde Phys., 3d series, iii.,p. 94. 



456 OF THE DROPPINGS OF BIRDS. 

SO much of this element as to account for all the effects which the oil 
is said lo have produced. 

While, then, we put so much faith in theory as to believe that sub- 
stances which contain much nitrogen are very likely to prove valuable 
manures, — we must not allow ourselves to be so carried away by the 
simplicity of the principle as Jo believe either that their relative effects 
upon our crops may be always estimated by the proportion of nitrogen 
they contain, or that a substance may not largely increase the produce 
of our fields in which no nitrogen is present at all. Indeed the effects 
of saline substances alone are sufficient to satisfy us how untrue to na- 
ture this latter opinion would be. 

§9.0/" the droppings of fowls — pigeons^ dung, and guano. 

The droppings of birds form one of the most powerful of known ma- 
nures. This arises in part from the circumstance that in the economy 
of birds there is no final separation between the liquid and solid excre- 
tions. Both escape mixed together from the same aperture. 

1°. Pigeons^ dung is much prized as a manure wherever it can be 
obtained in any considerable quantity. In Belgium it is esteemed as a 
top-dressing for the young flax, and the yearly produce of 100 pigeons 
is sold for about 20s. Its immediate effect depends upon the quantity 
of soluble matter it contains, and this varies much according to its age 
and the circumstances under which it has been preserved. Thus 
Davy* and Sprengel obtained respectively of 

Recent. Six months' old. After fermentation. 

(Davy.) (Sprengel.) (Davy.) 

Soluble matter in i oo * -ir i o * 

^w-^^ 'J i ^'^ per cent. lb per cent. o per cent, 

pigeons dung ^ ^ ^ ^ 

The soluble matter consists of uric acid in small quantity, of urate, 
sulphate, and especially of carbonate of ammonia, common salt, and 
sulphate of potash; — the iiisoluble chiefly of phosphate of lime, with a 
little phosphate of magnesia, and a variable admixture of sand and 
other earthy matters. f When exposed to moisture, the [)igeons' dung, 
especially if recent, undergoes fermentation, loses a portion of its am- 
moniacal salts, and thus becomes less valuable. When it is intended 
to be kept it should be mixed with a dry vegetable soil, or made into a 
compost with earth and saw dust, with a portion of pulverized or 
charred peat, or with such a disinfecting charcoal as that which is em- 
ployed in the manufacture of the animalized carbon above described. 

2*^. Hens^ dung often accumulates, decomposes, and runs to waste in 
poultry yards, when, with a little care, it might be collected in conside- 
rable quantities. 

3°. Goose dung is less rich than that of hens or pigeons, because this 
bird feeds less upon grain, and derives a considerable portion of its 
nourishment from the gra.ss which it crops, when allowed to goat liberty 
over the fields. Its known injurious effects upon the grass upon which 
it falls arise from its being in too concentrated a state. In moist weather, 
or where rain soon succeeds, it does no injury, and even when in dry 

* Davy's Agricultural Chemislry, Lecture VI. 
t Sprengel's Lehre vom Diinger, p. HO. 



COMPOSITION OF GtJAKO. 457 

weather it kills the blades on which it drops, it brings up the succeeding 
shoots with increased luxuriance. 

4°. Rooks' dung unites with the leaves of the trees among which 
they live, in enriching tlie pasture beneath them. In old rookeries the 
soil is observed also to be slowly elevated above the surrounding land. 
This surface soil I have found to be especially rich in phosphate of lime, 
which has gradually accumulated and remained in it while the volatile 
and soluble parts of the droppings of the birds have slowly disappeared. 

5°. Guano is the name given to the accumulated dung chiefly of sea 
birds, which is ff)und upon the rocky promontories, and on the islands that 
skirt the coast of South America, from the 13ih to the 21sT degree of 
south latitude. In that part of America, the climate being very dry, the 
droppings of the birds have decomposed with exceeding slowness, and 
upon some spots have continued to accumulate for many centuries, 
forming layers, more or less extensive, of 10, 20, and at certain places 
it is said even 60 (?) feet in thickness. In some places the more ancient 
of these deposites are covered by layers of drift sand, which tend fur- 
ther to preserve them from decay. In our moist climate the dung of 
the sea fowl is readily washed away by the rains, so that even where 
sea birds most abound no considerable quantity of guano can ever be 
expected to collect. 

The solid part of the droppings of birds in general, when recent, con- 
sists chiefly of uric acid, with a little urate of ammonia, and a variable 
per-centage of phosphate of lime and other saline compounds. The 
liquid part, like the urineof other animals, contains niuch urea, with some 
phosphates, sulphates, and chlorides. The uric acid and urea, however, 
gradually undergo decomposition, and are changed into carbonate and 
other salts of ammonia. If applied to the land when this stage of de- 
composition is attained, they form an active, powerful, and immediately 
operating manure; but if allowed to remain exposed to the air for a 
lengthened period of time, the salts of ammonia gradually volatilize, 
and the efficacy of what remains becomes greatly diminished. 
Hence, the guano which is imported into this country is very variable 
in quality, some samples being caf)able of yielding only 7 per cent, of 
ammonia, whileothers are said to give as much as 25 per cent. Of two 
portions taken by myself from the same box, the one contained 8 per 
cent, and the other only l\ per cent, of sand, while their other constitu- 
ents were as follows : — 

1°- percent.] "" 2°. percent. 
Water, salts of ammonia, and Ammonia .... 7-0 
organic matter expelled by Uric acid .... OS 
a red heat .... 23-5 Water and carbonic and ox- 
Sulphate of soda ... 1-S alic acids, &c., expelled by 
Common salt, with a little a red heat , . . 515 



percent. 


235 

1-S 


303 


44-4 


100 



phosphate of soda . . 30 3 Common salt, with a little 

Phosphate of lime, with a little sulphate and phosphate of 

phosphate of magnesia and soda , . . . 11-4 

carbonate of lime . . 444 Phosphate of lime, &c. • 29-3 

100 

On the other hand. Dr. Ure gives the following as the average result 
of his analyses of genuine guano: — 



458 VALUE OF GUANO AS A MANURE. 

percent. 
Organic matter containing nitrogen, including urate of ammonia, and 
capable of affording from 8 to 17 per cent, of ammonia by slow de- 
composition in the soil 50 

Water 11 

Phosphate of lime 25 

Ammonia, phosphate of magnesia, phosphate of ammonia, and oxalate 

of ammonia, containing from 4 to 9 per cent, of ammonia . . 13 

Siliceous matter from the crops of the birds 1 

]00* 

Others have found sand in much larger proportion than was present in 
the samples examined by myself — while it may, 1 think, be taken for 
granted that very little of what comes to this country is so rich in soluble 
matter, containlmj ammonia or its elements, as is represented by the 
analysis of Dr. Ure.f 

Variable as its composition is, however, there is now no doubt that 
any of the samples yet brought info the English market may be advan- 
tageously applied as a manure to almost any crop. Front the most 
remote period guano has been the chief manure applied to the land on 
the parched shores of Peru — and at the present day it is not only em- 
ployed for the same purpose in the provinces which lie along the coast, 
but it is also carried across the desert of Atacama many leagues iidand, 
*' on the backs of mules over rough mountain paths, and at a great ex- 
pense, for the use of the agricultural districts of Peru and Bolivia. "J It 
lias been estimated that a hundred thousand quintals|| are, at the present 
day, annually sold in Peru. There also the quantity and the price 
vary — the recent white guano selling usually at 3s. 6d., the more re- 
cent red and grey varieties at 2s. 3d. per cwt. (\Vinferreldi).§ In this 
country, the latter — the only variety yet imported — sells at present 
(1843), at about 10s. a cwt. 

In regard to the effects of guano upon various crops many important 
experimental results, obtained in 1842, will be foimd in the Appendix. 
I here insert a few of the more important of these, along with some 
others made in the more southern counties, which apjiear to be highly 
deserving of consideration. 



* By way of comparison, I insert here the approximate composilion of the solid part of the 
excrements of four different varieties of eagle, as delermined by Coindet: — ^ 

American American Grand Dnke 

Senegal Eagle. Huntinsr Eagle. Fishinji Eagle. of Virginia. 
Uric acid . . 80 79 90 37 64 65 88-71 

Ammonia . . 7 85 8 87 9 20 8 5.5 

Pho.sphateoflime 2-36 76 615 2-74 

100 100 100 100(a) 

(a) Gmelin Handbuch der Chemie, II., p. 1456. 

t The presence of ammonia in uuano is readily ascertained by mixing it with a little 
slaked lime— when the odour of ammonia will be immediately perceived, and will be strong 
In propnrtion to the qoaniiiy contained in the guano. 

t silliman's Journal, xliv., p. 10. 

II The quintal is equal to lOlilbs. avoirdupois. 

§ For furlher particulars rcfrardinsr guano the reader is referred to a paper in the Journal 
of the Royal AgricuUural Society^ II., p. 301. 



ITS ACTION' UPON TURNIPS, POTATOES, WHEAT, ETC 



459 



Top-dressed with 



2". 



3°. 



Farm-yard dung 
Guano 

Farm-yard dung 
Guano* 
Bones 

Guanot 

Rape-dust 

Bone-dust 



Guano 

Rape-dust 

Guano 

Rape-dust 

Bone-dust 

Guano 

Rape-dust 

Bone-dust 



20 
3 

20 
2i 
32 

5 
15 
30 



tons. 

cwt. 

tons. 

cwt. 

bush. 



11 



Swedish Turnips. 
rrotliice per acre, 
tons. cwt. 
18 
23 
IG 
17 
15 



Locality. 
> Barochan, near Paisley. 

4 > Parish of Wraxall, Somerset. 
\1) 

Yellow Turnips. 
cwt. 32 2) 

cwt. 24 11 > Barochan, near Paisley, 

bush. 17 2) 



Polaloes. 



3 cwt. 
1 ton. 

4 cwt. 
1 ton. 

45 bush. 

4 cwt. 

1 ton. 

45 bush. 



18 
12 
14 
10 
9 
13 
13 
13 



91 

f) 

6 

14 



14 



Barochan, In all these cases 
the manures were put in 
alone with the potatoe cut- 
tings, no other manure being 
afterwards added. 



As a top-dressing to the young potatoe crop at Erskine, in 1842, one cwt of 
guano per acre produced no important increase. This might, however, be ow- 
ing to the extreme diyness of the season (Appendix, No. IX.) 

Wheat. 



1°. 

2°. 
3°. 



Top-dressed with 



Prodiicp. per acre. 
bu.=5h. lbs. 



1°. 

2°. 



Guano 

Rape-dust 

Undressed 

G uano 

Undressed 

Guano 

Undressed! 

Guano 

Nitrate of Soda 

Undrt'ssed 

Guano 

Nitrate of Soda 

Undressed 

Guano 
Undressed 

Guano 
Undressed 
Guano 

Nitrate of Soda 
■ Undressed 



1 

16 



cwt. 
cwt. 



3 cwt. 
2 cwt. 



1 
1 

li 

U 



cwt. 
cwt. 



cwt. 
cwt. 



3 cwt. 



2 cwt. 



cwt. 
cwt. 



48 

51 

471 

30 

24 

32 

31 

4G 

51 

44 

45 

41 

39 

Barley. 
64 
47 

Oats. 
70 
52 
48 
50 
49 



Locality. 
) Lennox Love, near Hadding- 
> ton— 
) drought very great. 

40 ) 

rn^ Barochan. 

20 i 

oV > Gadgirth, near Ayr. 

18 > Erskine, Renfrewshire.il 

^} 

/- Seisdon, Worcestershire.§ 



0^ 

, P > Barochan. 



) Lennox Love, near Hadding- 
\ ton. 

> Erskine, Renfrewshire. 



• Mixed with 1 cwt. of charcoal powder. 

t Mixed wi'h 20 bushels of wood-ashes. 

t The iindres.-!ed grain was of superior quality, yielding 76^ per cent, of fine flour, while 
that dressed with jruano jraveonly 68f per cent. 

II The grain dressed with guano weighed half a pound per bushel less than the others. 

§ The guano gave 4 cwt. more straw than the nitrate, and 11 cwt. more than the undressed. 
The undressed grain also weighed half a pound less per bushel than either of the other two. 
39 



460 SOLID MATTER IN THE URINE OF DIFFERENT ANIMALS. 

Beans. 
Produce per acre, 
bush. 
Guano . . 2 cwt. 33 ^^ 

Nriof'soda: '? c^: 3I kenno. Love, near Haddington. 
Undressed . . 29 f J 



1°, Guano 

Nitrate of Soda 

Undressed 
2°. Guano 

Nitrate of Soda 

Undressed 



Hay. 
tons. cwt. 
\\ cwt. I 18) 

H cwt. 2 10 > Barochan, near Paisley. 

18) 
U cwt. 2 2 

li cwt. 1 17 /► Erskine, Renfrewshire. 



1 10) 



An inspection of the above results appears to indicate that guano is 
more uniformly successful with root crops, than when applied as a top- 
dressing to corn and grass. The unusual drought which prevailed in 
1842 no doubt materially diminished iis action, when used as a top- 
dressing — and the results upon the corn crops in a more moist season 
may probably prove more generally favourable to its use as an econo- 
mical manure. 

Some experiments seem already' to indicate that the favourable in- 
fluence of guano does not cease with the first season. If the phosphate 
of lime which they contain operate in any way in prolonging the fer- 
tilizing operation of bones, the large, though variable, quantity of this 
phosphate contained in guano should render this latter substance also 
capable of permanently improving the soil. 

By exposure to the air, guano gradually gives off a portion of its 
volatile constituents; it ouglit, therefore, to be kept in covered vessels 
or casks. It also in our climate absorbs moisture from the air, and 
therefore should be purchased as soon as possible after importation. 
When applied as a top-dressing it may be conveniently mixed with an 
equal weight of gypsum or wood-ashes — with charcoal powder, or with 
fine dry soil. 

§ 10. Of liquid animal manures — the urine of man, of the cow, the 
horse, the sheep, and the yig. 

The following table exhibits the average proportions of water, and of - 
the solid organic and inorganic matters contained in the urine of man 11 
and some other animals in their healthy stale — and the average quan- 
tity voided by each in a day : — 

Urine of 

Man 
Horse 
Cow 
Pig . 

Sheep 

• Alfred Becquerel. See Thomson's Animal Chemistry, p. 477. It is to be observed that 
the proportions of water and of solid matter in urine vary with the food, and with a great va- 
riety of circumstances. 

t A milk cow voids less than this in a proportion which varies with the quantity of milk 
she gives. Bonssingault found a milk cow to yield daily 18 lbs. of urine and 19 lbs. of milk. 
— Ann. de Chim. et de Pht/s., ]xxi., pp. 123, 124. 



Water 
in 


Solid matter in 1000 parts. 


Average quan 
lity voided in 
24 hours. 


1000 parts. 


Orjranic. 


Inorganic. 


Total. 


969* 


'23-4 


76 


31 


3 lbs. 


940 


27 


33 


60 


3 " 


930 


50 


20 


70 


40t ." 


926 


56 


18 


74 


7 


960 


28 


12 


40 


-i 



COMPOSITION OF HUMAN URINE. 461 

Of natural liquid manures, the most important and valuable, though 
the most neglected and ihe most wasted also, consist of the urine of 
man and of the animals he has domesticated. 

The efficacy of urine as a manure depends upon the quantity of 
solid matter which it holds in solution, upon the nature of this solid 
matter, and especially upon the rapid changes which the organic part 
of it is known to undergo. 

The numbers in the above table show that the urine of the cow, esti- 
mated by the quantity of solid matter it contains, is more valuable than 
that of any other of our domestic animals, with the exception of the pig. 
But the quantity voided by the cow must be so much greater than by 
the pig, that in annual value the urine of one cow must greatly exceed 
that of many pigs. 

It might be supposed at first that in all animals the quantity of urine 
voided would have a close connection with the quantity of water which 
each was in the habit of drinking. But this is by no means the case. 
Thus it is the result of experiment that in man the drink exceeds the 
urine voided by ahout one-tenth 'part only — while 

Of water in 24 hours. Of urine in 24 hours. 

A horse, which drank 35 lbs. gave only 3 lbs. 
A cow, which drank 132 lbs. gave 18 lbs., and 

19 lbs. of milk (Boussingault). 

How very large a quantity of the liquid they drink must escape from 
the horse and the cow in the form of insensible perspiration ! That this 
should be very much greater indeed than in man, we are prepared to 
expect from the greater extent of surface which the bodies of these ani- 
mals present. 

Let us now examine more closely the composition of urine, the 
changes which by decomposition it readily undergoes, and the effect of 
these changes upon its value as a manure. 

1°. Human urine. — The exact composition of the urine of a healthy 
individual in its usual state was found by Berzelius to be as follows : — 

Phosphate of soda . . 2-9 
Phosphate of ammonia . 1*6 
Common salt . • . 4'5 
Sal-ammoniac . . • 1'5 
Phosphates of lime and mag- 
nesia, with a trace of silica 
and of fluoride of calcium, 11 



Water 


^ 


9330 


Urea .... 


. 


301 


Uric acid , 


, 


1-0 


Free lactic acid, lactate of am- 




monia, and animal 


matter 




not separable . 


, 


171 


Mucus of the bladder . 


. 


0-3 


Sulphate of potash 


, 


3-7 


Sulphate of soda 


. 


3-2 



1000 



From what I have already had occasion to state in regard to the ac- 
tion upon living plants, of the several sulphates, phosphates, and other 
saline compounds, mentioned in the above analysis, you will see that 
the fertilizing action of urine would be considerable, did it contain no 
other sofid constituents. But it is to the urea which exists in it in very 
much larger quantity than any other substance, that its immediate and 
marked action in promoting vegetation is chiefly to be ascribed. This 
urea, which is a white salt-like substance, consists of — 

Carbon . . 20-0 per cent. I Nitrogen . . 46-7 per cent. 

Hydrogen . Q'Q " Oxygen . . 26-7 

~ 100 



462 



URIXE OF THE COW ITS VALUE. 



It is, therefore^ far richer in nitrogen than flesh, blood, or any of those 
otiier richly fertilizing subsiances, of which ihe main efficacy is sup- 
posed to depend upon the large proportion of nitrogen they contain. 

But urea possesses this further remarkable property, that when urine 
begins to ferment, — as it is known to do in a few days after it is voided 
—it changes entirely into carbonate of ammonia.* Of the ammonia 
thus formed a portion soon begins to escape into the air, and hence the 
strong ammoniacal odour of fermenting urine. This escape of ammo- 
nia continues for a long period, the liquid becoming weaker and weaker, 
and consequently less valuable as a manure every day that passes. Ex- 
perience has shewn that recent urine exercises in general an unfavoura- 
ble action upon growing plants, and that it acts most beneficially after 
fermentation has freely begun, but the longer time w^e suffer to elapse 
after it has reached the ripe state, the greater the quantity of valuable 
manure we permit to go to waste. 

2°. The urine of the cow has been analysed in several states by 

Sprengel, with the tbllowing results in 1000 parts : — 

Allowed to ferment for four weeks 
Fresh. 



Water . . . . 


926-2 


Urea 


400 


Mucus 


20 


Hippuric and lactic acids 


61 


Carbonic acid 


21 


Ammonia 


21 


Potash .... 


6-6 


Soda .... 


5-5 


Sulphuric acid 


40 


Phosphoric acid . 


07 


Chlorine 


27 


Lime .... 


0-6 


Magnesia 


0-4 


Alumina, oxide of iron, and 


oxide 


of manganese * 


01 


Silica . • • • 


0-4 



in the open 


air. 


A. 


B. 


954-4 


934-8 


100 


60 


0-4 


03 


7-5 


6-2 


1-7 


15 3 


4-9 


16-2 


Q(^ 


&G 


55 


5-6 


39 


33 


0-3 


15 


2-7 


2-7 


trace 


trace 


02 


04 


trace 





01 


01 



1000 998-2 9990t 

The first variet}^ of fermented urine (A.), had stood four weeks in the 
air in its natural state of dilution ; the second (B.), had been mixed 
"while recent with an equal bulk of water — which is again deducted from 
it in the analysis — with the view of ascertaining how far such an admix- 
ture would tend to retain the volatile ammonia produced by the natural 
decomposition of the urea. 

An inspection of these tables shews three facts of importance to the 
agriculturist — 

* This takes place by the decomposition at the same time of two atoms of the water in which 
it is dissolved. Tiius urea is represented by C:' HA N^ O2 ; two of water by 2 H O ; and car- 
bonate of ammonia by N H3 4 CO;^: and the change is tlius shewn— 

2 of 2 of 

Urea. Wafer. Carbonate of Ammonia. 

Ci H4 N2 O2 + 2 H O = 2 (N H3 + C O2) 
t The small quantity necessary to make up the 1000 parts in the two latter analyses con- 
sisted of a deposit of carbonate and phosphate of lime and other earthy matters which had 
gradually been formed, and of a trace of vinegfir and of suljihurelted hydrogen.— See Spren- 
gel, Lehre VQin Diijigeri pp, 107 to 110. 



I 



URINE OF THE HORSE, SHEEP, AND PIG. 4 33 

1°. That the quantity of urea in the urine of the cow is considerably 
greater than in that of man. 2°. That as the urine ferments, the quantity 
of urea diminishes, while that of ammonia increases — owing, as I 
have already stated, to the gradual decomposition of the urea and its 
ccnversion into carbonate of ammonia ; and, 3°. That by dilution with 
an equal bulk of water the loss of this carbonate of ammonia, which 
would otherwise naturally take place, is in a considerable degree pre- 
vented. The quantity of ammonia retained by the urine, after dilution, 
was in the same circumstances nearly three times as great as when it was 
allowed to ferment in the state in ivhich it came from the cow. 

But even by this dilution the whole of the ammonia is not saved. 
One hundred parts of urea form by their decomposition 56i parts of am- 
monia, and as 36 parts of the urea in the urine B. had disapppeared, 
there ought to have been in its stead 19 parts of ammonia in addition to 
that which the urine contained in its recent state, or 21 parts in all — 
whereas the table shews it to have contained only 16 parts. Even when 
diluted with its own bulk of water, therefore, the urine had lost by fer- 
mentation in the open air upwards of one-fourth of the ammonia pro- 
duced in it during that period. This shews the necessity of causing our 
liquid manures to ferment in covered cisterns, or of adopting some other 
means by which the above serious loss of the most valuable constituents 
may be prevented. 

3°. The urine of the horse, sheep, and pig, have not been so carefully 
analysed as that of the cow. They consist essentially of the same con- 
stituents, and the specimens which have been examined were found to 
contain the three most important of these in the following proportions : 

Ilorse. Sheep. Pig. 

Water 940 960 926 

Urea 7 ? 28 56 

Saline substances . 53 12 18 

1000 1000 1000 

Some of the saline substances present in the urine, as above stated, 
contain nitrogen. This is especially the case in the urine of the horse, 
so that the quantity of urea above given is not to be considered as repre- 
senting the true ammonia-producing power of the urine of this animal. 
The urine of the pig, if the above analysis is to be relied upon as any 
thing like an average result, is capable of producing more ammonia from 
the same quantity than that of any other of our domestic animals. 

§ 11. Of the waste of liquid manure — of urate, and of sulphated urine. 

1°. Waste of human urine. — The quantity of solid matter contained 
in the recent urine voided in a year by a man, a horse, and a cow, and 
the weight of ammonia they are respectively capable of yielding, may 
be represented as follows : — 

Quantity of iirine. Solid matter. Containing of urea. And yielding of ammonia, 
Man 1000 lbs. 67 lbs. 30 lbs. 17 lbs. 

Horse 1000 " 60 " 1 '? 

Cow 13000 '' 900 " 400 " 230* " 

• The numbers given above, and in p. 460, are calculated from the ?nalypis of the urine of 
the horse by Fourcroy and Vnuqiieliii, and of that of tlie cow by Sprengcl. Boussingault, 
however, obtained verv diire'reat results. Thus a cow and a horse, on wliich his experi- 
39* 



464 URATE, AND SDLPHATED URINE. 

How much of all ihis enriching matter is permitted to run to waste ? 
The solid substances contained in urine, if all added to the land, would 
be more fertilizing than guano, which now sells at c€lO. a ton. If we 
estimate the urine of each individual on an average at only 600 lbs., 
then there are carried into the common sewers of a city of 15,000 in- 
habitants, a yearly weight of 600,000 pounds, or 270 tons, of manure, 
which, at the present price of guano, is worth c£2700, — which would no 
doubt prove more fertilizing than its own weight of guano, and might be 
expected to raise an increased produce of not less than 1000 qrs. of grain. 

The saving of all this manure would be a great national benefit, 
though it is not easy to see by what means it could be effectually ac- 
complished. What is thus carried off by the sewers and conveyed ul- 
timately to the sea, is drawn from and lost by the land, which must, there- 
fore, to a certain extent be impoverished. Can we believe that in the 
form offish, of sea tangle, or of spray, the sea ever delivers back a tithe 
of the enriching matter it daily receives from the land ? 

2°. Urate. — In order to prevent a portion of this waste, the practice 
has been introduced into some large chies of collecting the urine, adding 
to it one-seventh of its weight of powdered gypsum, allowing the whole 
to stand for some days, pouring off the liquid and drying the powder. 
Under the name of urate this dry powder has been highly extolled, but 
it can contain only a small portion of what is really valuable in urine. 
The liquid portion poured off must contain most of the soluble aramo- 
niacal and other salts, and even were the whole evaporated to dryness, 
the gypsum does not act so rapidly in fixing the ammonia as to prevent 
a considerable escape of this compound as the fermentation of the urine 
proceeds. 

3°. Sulphated urine. — A method of more apparent promise is that 
now practised by the Messrs. Turnbull, of Glasgow, of adding diluted 
sulphuric acid to the urine as the ammonia is formed in it, and subse- 
quently evaporating the whole to dryness. From the use of this sub- 
stance very favourable results may be anticipated.* Still none of these 
preparations will ever equal the urine itself, part of the efficacy of which 
depends upori the perfect state of solution in which all the substances 
it contains exist, and upon the readiness with which in this state they 
make their way into the roots of plants. 

4°. Loss of coivs' urine.— -'When left to ferment for five or six weeks 

ments were made, yielded a quantity of urine which in a year would have amounted to, and 
would have contained, mj3ou7kfe — 

Containing of Capable of yield- 

Quantity. Solid matter (total). Inorganic matter. Nitrogen, ing of ammonia. 

Cow 6570 773 309 29 35 

Horse 1100 243 89 30 36 

The cow yielded at the same time 19 lbs. of milk each day, which accounts for the 

smaller proportion of urine vcided, than is given in the text. It is remarkable, however, 

that the quantity of nitrogen contained in an equal weight of the urine of the horse was in 

this case so much greater than in that of the cow— and that the whole amount which would 

have been yielded by that of the cow in a year should be so very much less than in the re- 

• suit obtained by Sprengel. The milk did not coniain nitrogen sufficient to yield more than 45 

lbs. of ammonia, and this, added to the 35 lbs. makes only 80 lbs; in all— whereas Sprengel 

gives 2-30 lbs. as the quantity which recent urine is capable of yielding. This remarkable 

difference must be ascribed either to an actual loss of volatile matter by the urine analysed 

by Boussingaulf, or— which is more probable— to a diflference in the quality of the food on 

which the two animals were fed. 

•The Messrs. Turnbull inform me that with this sulphated urine, under the incorrect 
name o\ sulphate of ammonia, the experiments of Mr. Burnet were made (p. 362), as well aa 
those of Mr. Fleming and Mr. Alexander, detailed in tne Appendix. 



' LOSS OF LIQUID MANURE IN THE FARM-YARD. 465 

alone, and with the addhion of an equal bulk of water, the urine of the 
cow loses, as we have seen, a considerable proportion of volatile matter, 
and in these several states will yield in a year — 

Solid Tnatler. Yielding of ammonia. 

Recent urine 900 lbs. 226 lbs. 

Mixed with water, after 6 weeks . 850 " 200 " 

Unmixed, after 6 weeks . . . 550 " 30 " 

Those who scrupulously collect in tanks and preserve the liquid ma- 
nure of their stables, cow-houses, and fold-yards, will see, from the great 
loss which it undergoes by natural fermentation, the propriety of occa- 
sionally washing out their cow-houses with water, and, by thus dikiting 
the liquid of their tanks, of preserving the immediately operating con- 
stituents of their liquid manure fri>m escajting into the air. Even when 
thus diluted il is desirable to convey it on to the land whhout much 
loss of time, since even in this state there is a constant slow escape, by 
which its value is daily diminished. Gypsum, sulphate of iron, and 
sniphuric acid, are, by some, added for the purpose of j^.rzw^ the ammo- 
nia, but in addition to diluting it, an admixture of rich vegetable soil, 
and especially of peat, will be much more economical, and — except in 
so far as the gypsum or sulphuric acid themselves act as manures — 
nearly as effectual. 

But these remarks apply only to the liquid manure when collected. 
How much larger a waste is incurred by those who make no effort to 
collect the urine of their cow-houses or stables! The recent urine of 
one cow is valued in Flanders — where liquid manures are highly es- 
teemed^at 40s. a year. It contains on an average, as we have seen, 
900 lbs. of solid matter, and this estimated at the price of guano only, 
is worth at present 6£4. sterling. Multiply this by 8 millions, the num- 
ber of cattle said to exist in the United Kingdom, and we have 32 mil- 
lions of pounds sterling, as the value of the urine, supposing it to be 
worth no more than the foreign guano. It is impossible to estimate how 
much of this runs to waste, but one-tenth of it will amount to nearly as 
much as the whole income-tax recently laid upon the country. The 
practical farmer who uses every effort to collect and preserve the ma- 
nure which nature puts within his reach, is deserving of praise when he 
expends his money in the purchase of manures brought frotn a distance, 
of whatever kind they may be ; but he, on the other hand, is only open to 
censure who puts forward the purchase of foreign manures as an excuse 
for the neglect of those which are running to waste around him. Let every 
stock farmer, with the help of the facts above stated, make a fair calcula- 
tion of what is lost to himself and to the country by the hitherto unheeded 
waste of the urine of his cattle, and he will be able clearly to appreciate 
the importance of taking some steps for preserving it in future. 

§ 12. Of solid animal manures — night soil, the dmig of the cow, the 
horse, the sheep, and the pig. 

1°. Night soil is in general an exceedingly rich and valuable manure, 
but its disagreeable odour has in most countries rendered its use unpopu- 
lar among practical men. This unpleasant smell may be in a great 
measure removed by mixing it with powdered charcoal or with half- 
charred peat, — a method whicli is adopted in the manufacture of cer- 



466 NIGHT SOIL READILY DECOMPOSES — ITS COMPOSITION'. 

tain artificial manures. Quick-lime is in some places employed for the 
same purpose, but though the smell is thus got rid of, a large portion of 
the volatile ammonia produced during the decomposition of the manure 
is at the same time driven off by the lime. 

In general, night soil contains about three-fourths of its weight of 
water, and when exposed to the air undergoes a very rapid decomposi- 
tion, gives off much volatile matter — consisting of ammonia, of car- 
bonic acid, and of sulphuretted and phosphuretted hydrogen gases — and 
finally loses its smell. In the neighbourhood of many large cities, the 
collected night soil is allowed thus naturally to ferment and lose its smell, 
and is then dried and sold for manure, under the name o[ poudretle. 

But by this fermentation a very large proportion of valuable matter 
is permitted to escape into the air. To retain this, gypsum or dilute 
sulphuric acid may be added to the night soil, but the more economical 
and generally practicable method is to mix it with earth rich in vege- 
table matter, with partially dried peat, with saw-dust, or with some 
other readily accessible absorbent substance. In this way a rich and 
fertilizing compost will be obtained, which will have little smell, and 
yet will retain most of the virtues of the original manure. 

In China, the fresh night soil is mixed up with clay and formed into 
cakes, which when dried are sold nnder the name of Taffo, and form 
an extensive article of commerce in the neighbourhood of the larger cities. 

The composition of night soil, and consequently its value as a ma- 
nure, varies with the food, and with many other circumstances (p. 470). 
The excrements of a healthy man were found byBerzelius to consist of— 

Water 733 

Albumen ........ 9 

Bile 9 

Mucilage, fat, and other animal matters . . 167 
Saline matter ....... 12 

Undecomposed food ...... 70 

1000 
Of the excrement when freed from water 1000 parts left 132 of ash, 
consisting of — 

Carbonate of Soda 8 

Sulphate of Soda, with a little Sulphate of Potash, and 

Phosphate of Soda 8 

Phosphate of Lime and Magnesia, and a trace of Gypsum 100 
Silica 16 

132 
2°. Cow dung forms by far the largest proportion of the animal ma- 
nure which in modern agriculture is at the disposal of the practical 
farmer. It ferments more slowly than night-soil, or than the dung of 
the horse and the sheep. In fermenting it does not heat much, and it 
gives off little of an unpleasant or ammoniacal odour. Hence it acts 
more slowly, though for a longer period, when applied to the soil. 

The slowness of the fermentation arises chiefly from the smaller 
quantity of nitrogen, or of substances containing nitrogen, which are 
present in cow dung, but in part also from the food swallowed by the 
cow being less perfectly masticated than that of man or of the horse. It 



HORSE DUWG SPEEDILY FERMENTS, AND LOSES WEIGHT. 467 

is a consequence of this slower fermentation, that the same evolution of 
ammoniacal vapours is not perceived from the droppings of the cow as 
from nifjht soil and from horse dung. Yet by exposure to tlie air, it un- 
dergoes a sensible loss, which in 40 days has been found to amount to 5 
per cent, or nearly one-fifth of the whole solid matter which recent cow 
dung contains.* (Gazzeri.) Although, therefore, the comparatively 
slow fermentation as well as the softness of cow dung fits it better for 
treading among the straw in the open farm-yard, yet the serious loss 
which it ultimately undergoes will satisfy the economical farmer that 
the more effectually he can keep it covered up, or the sooner he can 
gather his mixed dung and straw into heaps, the greater firoportion of this 
valuable manure will he retain for the future enriching of his fields. 

3°. Horse dang is of a warmer nature than that of tlie cow. It heats 
sooner, and evolves much ammonia, not merely because it contains less 
water than cow dung, but because it is generally also richer, in those 
orijanic compounds of which nitrogen forms a constituent part. Even 
when fed upon the same food the dung of the horse will be richer than 
that of the cow, because of the greater proportion of the food of the lat- 
ter which is discharged in the large quantity of urine it is in the habit of 
voiding (p. 470). 

In the short period of 24 hours, horse dung heats and begins to suffer 
loss by fermentation. If left in a heap for two or three weeks scarcely 
seven-tenths of its original weight will remain. Hence the propriety 
of early removing it from the stable, and of mixing it as soon as possible 
with some other material by which the volatile substances given off may 
be absorbed and arrested. The colder and wetter cow or pig's dung 
will answer well for this purpose, or soil rich in vegetable matter, or peat, 
or sawdust, or powdered charcoal, or any other absorbent substance which 
can readily be obtained — or if a chemical agent be preferred, moistened 
gypsum maybe sprinkled among it, or diluted sulphuric acid. There 
is undoubtedly great loss experienced from the general neglect of night 
soil, but in most cases the dung of the horse might also be rendered a 
source of much greater profit than it has hitherto been. 

The warmth of horse dung fits it admirably for bringing other sub- 
stances into fermentation. With peat or sawdust it will form a rich 
compost, and to soils which contain much inert vegetable matter it can 
be applied with great advantage. Horse and cow dung, iii the dry state, 
have been subjected to ultimate analysis by Boussingault*, with the fol- 
lowing results : — 

Dung of the Horse. Dung of a Milk Cow. 

Carbon 387 42 8 

Hydrogen 5*1 5-2 

Oxygen 377 37-7 

Nitrogen 22 23 

Ashes • lG-3 12 



100 100 

Watert 300 566 



400 em 



* Cow (hmz non'lsrinaof?-" ofwateranrl 2o<)filry solid matter, of which latter 5 disappear. 

1 Annates de Chim. ef de Phys , Ixv., pp. 122 and 134. 

t Recent horse dung losing 75 per cent, of water by drying, of cow dang 75 per cent. 



468 THE DUNG OF THE PIG AND THE SHEEP. 

The proportion of nitrogen contained in the two manures, according 
to these results, is so nearly alike — being in reality greater in the cow 
dung — that were we to consider the above numbers to represent the ave- 
rage constitution of the droppings of the horse and cow, we should be 
compelled to ascribe the difference in their qualities solely to the different 
states in which the elements exist in the two, and to the proportions of 
"^vater they respectively contain. But the nature of the food and other 
circumstances affect the quality of these manures so much (p. 470), that 
we cannot as yet draw any general conclusion from the results obtained 
in one special case. 

4°. Pig's dung is still colder and less fermentable than that of the 
cow. It is characterized by an exceedingly unpleasant odour, which 
when applied to the land alone it imparts to the crops, and especially to 
the root crops which are manured with it. Even tobacco, when ma- 
nured with pig's dung, is said to be so inuch tainted that the leaves sub- 
sequently collected are unfit for smoking.* It is a good manure for hemp 
and other crops not intended for food, but is best employed in a state 
of mixture with the other manures of the farm-yard. 

5°. Sheep's dung \s ?i rich dry manure, which ferments more readily 
than that of the cow, but less so than that of the horse. A specimen 
examined by Zierl consisted of — 

Water 68-0 per cent. 

Animal ^nd vegetable matter . . . 19-3 " 

Saline matter, or ash 12*7 *' 



100 

The food of the sheep is more finely masticated than that of the cow, 
and its dung contains a little less water, and is probably richer in nitro- 
gen ; hence its more rapid fermentation. When crops are eaten off by 
sheep, their manure is more evenly spread over the field, and is, at the 
same time, trodden in. When thus spread it decomposes more slowly 
than when it is collected into heaps, and the ammonia and other useful 
products of the decomposition are absorbed in great part by the soil as 
they are produced. Those soils in which a considerable quantity of 
vegetable matter is already present, are said to be most benefitted by 
sheep's dung, because of the readiness with which they absorb the vola- 
tile matters it so soon begins to give off. 

Sheep's dung is said to lengthen the straw of the corn crops, and to pro- 
duce a grain rich in gluten — and unfit therefore for seed, for the manufac- 
ture of starch, or for the purposes of the brewer and the distiller (Spren- 
gel). It may be doubted, however, whether these can as yet be safely 
considered as the universal effects of sheep's dung upon every soil, and 
when the animals are fed upon every kind of food. 

§ 13. Of the quantity of manure produced fi om the same kinds of 
food by the horse, the cow, and the sheep. 

The carefully conducted experiments of Block give the following as 
the total quantities of manure, solid and liquid, produced from 100 lbs. of 
the different kinds of food by the cow, the horse, and the sheep. 

• Sprenjel, Lehre vom Dunger, p. 38. 



MA^URE PRODUCED BY DIFFERE>T ANIMALS. 



469 



Quantity of manure in lbs., produced by 



From 100 lbs. of 



THE cow. 
fresli. dried. 



Rye • . . . 

Oats _ _ 

Rye and other straws (chopped) 2G8 43 
Hay . ... . 275 44 
Potatoes (containing 72 per ct. 

of water) 
Turnips (containing 75 per cent 

of water) ... 37^ 6 

Carrots (87 per cent, of water) 37A 6 
Green Clover (79 per ct. water) 65? 9 « 



THE HORSE. 

fresh, drit'd. 
212 53 



THE SHEEP. 

fresh, driid. 



204 
1G8 
172 



871 14 — 



51 
42 
43 



117 
123 



40 
42 



Water in 

the manure, 

percent. 

75 

75 

6G to 84 

do. do. 



33 13 do. do. 

— — 84 

— — 84 

— — 86 



After 8 days. After 3 weeks. After 8 weeks. 
Rye Straw (used for bedding) 238 96 269 97 206 95 54 to 64 

One important theoretical re.siilt is presented by (Jiis table — that the 
manure voided by an animal contains very much (.ess solid matter than the 
food it has consumed. We shall |)resently see how this fact is to he ex- 
plained (p. 472), and, at the same litiie, what light it throws upon the 
quality ot^ the manure j)roduced. 

The most valuable practical results fro tii the above experiments ^ire — 

1°. That for 100 lbs. of dry fodder the horse or the cow will give on 
an average 216 lbs. of fresh or 46 lbs. of dry manure — the sheep 128 
lbs. moist or 43 lbs. dry. 

2^*. That root crops, on an average, give about half their weight of 
fresh or one-twelfih of dry manure — the potaioe giving more and the 
turnip less. 

3°. That green crops give about half their weigiit of fresh or one- 
eighth of dry manure. 

§ 14. Of the relative fertilizing values of different animal excretions. 

1°. The theoretical value of dilTerent anitnal excretions calculated 
solely from the quantity of nitrogen which the specimens examined were 
found respectively to contain, is thus given by Payen and Bou.'^singault. 
The numbers opposite to each substance indicate the weights of that 
substance which ought to produce an ecjual effect with 100 lbs. of farm- 
yard manure in the recent and in the dry states: — 

Equal effects ought be produced by 
in tlie dry state. artificially dried. 
Farm-yard dung ... " 

Cow . . . , . 
Do. urine .... 
Horse ..... 
Mixed excrements of the — Pig 

Horse 

Sheep 

Pigeon 

Poudrett 

A n other 

Too much reliance is not in any case to l)e placed upon the principle 
of classifying manures solely by the jiroportion of nitrogen they contain 
(pp.^441 & 454) — much less can we depend ujjon the order of value it 
assigns to substances the com posit ion of which is liable to constant change 



100 lbs. 


100 lbs 


125 " 


84 " 


91 " 


51 " 


73 " 


88 " 


63 " 


58 " 


54 " 


64 " 


36 " 


65 " 


5 " 


22 " 


te . lOi " 


44 « 


r variety 26 '* 


73 " 



Wheat. 


Barley. 


Oals, 


Rye. 


14 


16 


I2i 


14 


— 


13 


141 


13i 


12 


16 


14 


13 


— 


13| 


13 


13 


10 


13 


14 


11 


— 


10 


12 


9 


7 


11 


16 


9 


3 


7 


13 


6 


— 


4 


5 


4 



470 FERTILIZING VALUES OF ANIMAL EXCREtlOli?S. 

from the escape of those volatile compounds in which the nitrogen prin- 
cipally exists. 

2°. A series of experiments made by Hermbstadt upon the quantity 
of grain of different kinds, raised in the same circumstances by equal 
weights of different manures, gave the following results : — 

Number of seeds reaped from_ 
Manure applied. 
Ox blood 
Night soil . 
Sheep's dung 
Human urine 
Horse dung 
Hgeon dung 
Cow dun^ . 
Vegetable matter . 
Unmanured . 

If the results contained in this table were to be depended upon, it 
would appear that, in so far as the quantity of the produce is concerned, 
these manures severally exercise a special action upon -jertain crops — 
that night-soil, for example, is most propitious to rye, cow dunglo oats, 
and sheep's dung to barley and wheat. And the latter fact would seem 
at once to justify and to recommend the eating off' with sheep prepara- 
tory to either of the latter crops. 

None of these kinds of manure, however, is constant in composition, 
and the following observations will satisfy you that implicit reliance 
ought not to be placed either upon the relative practical values of the 
ditterent animal manures as they appear in the latter table, nor on their 
theoretical values as exhibited in the former. 

§ 15. Influence of circumstances on the quALiTT of animal manures. 

The quality of the droppings of animals considered as manures is af- 
fected by a great variety of circumstances — such as 

1°. By the kind of food upon which the animal is fed. — Thus night 
soil is more valuable in those countries and districts in which much 
flesh meat is consumed, than where vegetable food forms the principal 
diet of the people. It is even said by Sprengel, that in the neighbour- 
hood of Hildesheim the farmers give a higher price for the house ma- 
nure of the Lutheran than for that of the Roman Catholic families, be- 
cause of the numerous fasts which the latter are required to observe.* 
Every keeper of stock also knows that the manure in his farm-yard is 
richer when he is feeding his cattle upon oil-cake, than when he gives 
them only the ordinary produce of his farm.f 

2°. By the quantity of urine voided by the animal. — Upon the unlike 
quantities of urine they produce appears mainly to depend the unlike 
richness of the dung of the horse and of the cow. The latter animal, 
when full grown and not in milk, voids nearly 13 times as much urine 
as the forn^er (p. 460), and though an equal bulk of this urine is poorer 
in solid matter, yet the whole quantity contains several times as much 

* Lchre vom Dicnger, p. 142. 

t 12 loaHs of the dung of animals fed (while f^ttenin?) chiefly upon oil-cake was fmind to 
givf! a ^rreater produce than 24 loads from store stock fed in the straw yard. —Co7«j>toe Grazier, 
sixth edition, p. 103. 



ANIMAL MANURES AFFECTED BY MANY CIRCUMSTANCES. 471 

as is present in that of the horse. But if the cow discharges more in 
its urine it must void less in its solid excretions. Hence, supposing the 
food of a full-grown horse and of a cow to be very nearly the same, the 
dung of the former — the less urine-giving animal — must be the richer, 
the warmer, and the more valuable — as it is really known to be. 

3°. By the amount of exercise or labour to u/iic/i the animal is sub- 
jected. — The greater the fatigue to which an animal is subjected the 
richer the urine is found to be in those compounds (urea chiefly) which 
yield ammonia by their decomposition (Prout). The food of two ani- 
mals, therefore, being the same — other things also being equal — the 
solid excretions will be richer and more fertilizing in that which is kept 
in the stall or fold-yard, the larine in that which is worked in ibe open 
air or pastured in the field, 

4°. By the slate of growth to which the animal has arrived. — A full- 
grown animal has only to Jceep up its weight and condition by the food 
it eats. Every thing which is not necessary for this purpose, there- 
fore, it rejects either in its solid or in its liquid excretions. A young 
animal, on the other hand, adds to and increases its bone and muscle at 
the expense of its food. It rejects, therefore, a smaller proportion of 
what it eats. Hence the manure in fold-yards, where young cattle are 
liept, is tilways less rich than where full-grown animals are fed. 

5°. By the purpose for which tlie animal is fed. — Is it to be improved 
in condition ? Then the food must supply it with the materials for in- 
creasing the size and strength of its muscles — with albumen, or fibrin, 
^r other substances containing nitrogen. In such subslawces, therefore, 
or in nitrogen derived from tliem, the droppings must 'be poorer, and as 
a manure, less valuable. 

Is the animal to be fattened ? Then its food must supply fatty mat- 
ters, or their elements, of which nitrogen forms no part. All the nitro- 
gen of the food, therefore, will pass off in the excretions, and hence the 
richest manure yielded at any time by the same species of animal is 
that which is obtained when it is full-grown, and, being largely fed, is 
rapidly fattening- 

Is the cow kept for its milk ? Then the milk it yields is a daily drain 
upon the food it eats. Whatever passes into the udder is lost to the 
dung, and hence, other things being equals the dung of a milk cow will 
be less valuable to the farmer than that of a full-grown animal from 
which no milk is expected, or than that of the same animal when it is 
only laying on fat. 

6°. By the length of time during which the manure has been kepi. — 
In 24 hours, as we have seen, the dung of the horse begins to ferment 
and to lessen in weight. All rich manures in like manner — the dung 
of all animals especially — decompose more or less rapidly and part with 
their volatile constituents. The value we assign to them to-day, there- 
fore, will not apply to them to-morrow, and hence the droppings of the 
same animal at the same age, and fed in the same way, will be more or 
less valuable to the farmer according to the length of time during which 
they have been permitted to ferment. 

7°. Lastly. By the way in which the manure has been preserved. — The 
mixed dung of the farm-yard must necessarily be less valuable where 
the liquid manure is allowed to run off^ — or where it is permitted to 
40 



472 CHANGES PRODUCED UPON THE FOOD 

Btand in pools and ferment. Twenty cart-loads of such dung may 
hasten the growth of tlie turnip crop in a less degree than half the 
weight will do, where the liquid manure has heen carefully collected 
and returned upon the heaps — to hasten and complete their fermenta- 
tion, and to saturate them with enriching matter. 



Since, then, the quality orrichness of the dung of the same animal is 
liable to be affected by so many circumstances — it is obvious (hat no ac- 
curate general conclusions can be drawn in regard to its precise fertili- 
zing virtue when applied to this or to thatcrop, or to its relative fertilizing 
value when compared with equal weights of the dung of oilier animals. 
The results obtained in one set of analyses, as in that of Boussingault, 
or in one series of practical experiments, as in that of Hermbsiiidt (p. 
470), will not agree with those obtained in any other — because the sub- 
stances themselves with which our different experiments are made, 
though called by the same name, are yet very unlike in their chemical 
properties and composition. 

§ 16. Of the changes which the food undergoes in passing through 
the bodies of animals. 

It is the result of long experience that vegetable matter is more sen- 
sibly active as a manure, after it has passed through the body of an ani- 
mal, than if applied to the land in its unmasticated and undigpsied state. 
In becoming animalized, therefore — as it has been called — vegetable 
substances have been supposed to undergo some mysterious, because 
Dot very obvious or intelligible, internal change, by which this new vir- 
tue is imparted to them. Yet the change is very simple, and when ex- 
plained is not more satisfactory than it is beautiful. 

You will recollect, as I have already staled to you (p. 469), that the 
weight of dry manure voided by an animal is aluays considerably less 
than that of the dry food eaten by it. Upon the nature and amount of 
this loss which the food undergoes depends the quality of the manure 
obtained. 

This you will readily comprehend from the following statement : 

1°. Every thing which enters into the body in the form of food must 
escape from the body in one or other of three different forms. It must 
be breathed out from the lungs, perspired by the skin, or rejected in the 
solid or liquid excretions. We have already seen (Lee. VJIL, § 3), 
that the function of the lungs is to give off' carbon in the form of car- 
bonic acid, while they drink in oxygen from the air — and that the quan- 
tity of carbon thus given off' by a healthy man varies from 5 to 13 or 
more ounces in the 24 hours. From the skin also carbon escapes along 
with a small and variable proportion of saline matter. The weight of 
carbon given off" by the skin has not been accurately ascertained. Let 
us leave it out of view for a moment, and consider solely the efl^ect of 
respiration upon the nature of the solid and liquid excretions. 

Suppose a healthy man, taking a moderate degree of exercise, to give 
off" from his lungs 6 ounces of carbon in 24 hours, and to eat during the 
same time 2 lbs. of potatoes, half a pound of beef, and half a pound of 
bread. Then he has taken in his food — 



4 



BT PASSING THROUGH THE BODIES OF ANIMALS. 473 

Carbon. Nitrogen. Saline matter. 

In the potatoes . . . . 1716 grs. 47 grs. 196 grs. 

In the bread 1004 " 34 " 22 " 

In the beef 790 " 120 " 35 " 



3510 grs. 201 grs. 253 grs. 
And he has given off in respiration 2625 " 
Leaving to be rejected sooner or 

later in the excretions . . 885 " 201 " 253 " 

In this supposed case, therefore the carbon, nitrogen, and saliae mat- 
ter were to each other nearly as the numbers 

Carbon. Nitrogen. Saline matter. 
35 2 2i in the food, 

and as 9 2 2k in the excretions ; 

Or, in other words, the carbon being in great part sifted out of the 
food by the lungs, the excretions are necessarily much richer in nitrogen 
and in saline matter, weight for weight, than the mixed vegetable and 
animal matters on which the man has lived. 

But the immediate and most sensible action of animal and vegetable 
substances, as manures, depends upon the proportion of nitrogen and sa- 
line matters they contain. This proportion, then, being greater in the ex- 
cretions than in the crude vegetables, the cause of the higher estimation 
in which the former are held by the practical farmer is sufficiently clear. 

2°. In the above case 1 have supposed the allowance of food to be 
such only as a person of sedentary habits would consume, and the 
quantity of carbon given off from the lungs to be such as his habits 
would occasion. But if the weight of carbon given off from the lungs 
and skin together amount, as it often does, to 15 ounces,* the quantity 
of food must be greatly increased beyond the quantity I have stated, if 
the health and strength are to be sustained. By such an increase of 
food — the carbon being removed by respiration — the proportion of ni- 
trogen and of saline matters in the excretions may be still further in- 
cre'ased, or as manures they may become still richer and more immedi- 
ately fertilizing. 

3°. Let me present to you the results of an actual experiment made 
by Boussingault upon a horse fed with hay and oats — and of which both 
the food and the excretions were carefully analysed. 

In 24 hours the horse consumed — 

Carbon. Nitrogen. Saline matter. 

Hay, I6i lbs.,t containing . 45,500 grs. 1,500 grs. 8,960 grs. 

Oats, 5 lbs 15,000 " 650 " 1,180 " 



Total in the food . . . 60,500 '' 2,150 " 10,140 " 

And gave off from the lungs & skin 37,960 " 

Leaving to be rejected in the ex- 
cretions ..... 22,540 " 2,150 '' 10,140 " 

While there was actually found 

in the mixed dung . . . 22,540 '' 1,770 " 10,540 " 

* Liebig estimates the quantity oT carbon which escapes from the lungs and skin of a 
healthy min, taking moderate exercise, at 13 93 ounces (Hessian), or 15)^ ounces avoirdu- 
pois, in 24 hours. , m i • loc 

t Each containing about 14 per cent, of water.— vlnnaZes de Chim. et de Phys., lxxi.,p. IcJb. 



474 STATE i:^ WHICH FARM-YARD MANURE CAN BE 

In this case, then, the carbon, nitrogen, and saline matter were con- 
tained in the proportion of — 

Carbon. Nitrogen. Saline matter. 

28 1 5 in the food, 

and of lOi 1 5 in the dung ; 

The analysis of the dung itself proving that in passing through the body 
of an animal, the food — 
a diminishes very considerably in weight ; 
b losing a large but variable proportion^of its carbon, 
c but parting with scarcely any of its nitrogen and saline matter— 
and therefore 

d that the fertilizing virtues of the dung above that of the food of ani- 
mals— iveight for weight—depends mainly upon the larger proportion of 
these two constituents (the nitrogen and the saline matter) which the 
dung contains. 

I have only further to remind you upon this subject, that the state of 
combination also in which the nitrogen exists in the excretions has a 
material influence in rendering their action more immediate and sensi- 
ble than that of unchanged vegetable matter. It passes off for the most 
part in the form of urea, which is resolved into ammonia and its com- 
pounds more rapidly than the albumen of the dried or even of the recent 
plant, and is thus enabled sooner to exert an appreciable influence upon 
the growing crop. 

§ 17. Of farin-yard manure, and of the state in which it ought 
to he applied to the land. 

The manure of the farm-yard consists, for the most part, of cow-dung 
and straw mixed and trodden together, in order that the latter may be 
brought into a state of decomposition. In the improved husbandry, 
where green crops are extensively grown and many cattle are kept, the 
horse dung forms only a small proportion of the whole manure of the 
farm -yard. 

On an average, the quantity of recent manure obtained in the farm- 
yard amounts to a little more than twice the weight of the dry food of 
the cattle and of the straw spread in the farm-yard or in the stables 
(p. 469). That is to say, for every 10 cwt. of dry fodder and bedding, 
20 to 23 cwt. of fresh dung may be calculated upon. But if green 
clover or turnips (every 100 lbs. of which contain from 70 to 90 lbs. of 
water) be given to the cattle, an allowance must be made for the water 
they contain— -the quantity of mixed manure to be expected being from 
2 to 2i times the weight of the dry food and fodder only. 

But the recent manure loses weight by lying in the farm-yard. The 
moisture evaporates and volatile matters escape by fermenlalion. By 
the time that the straw is half-rotten this loss amounts to one-fourth of 
the whole weight, while the bulk is diminished one-half. If allowed to 
he still longer the loss increases, till at length it may approach to one- 
half of the whole, leaving a weight of dung little greater than that of 
the food and straw which have been consumed. The weight of com- 
mon mixed farrri-yard dung, therefore, obtained from 10 cwt. of dry food 
and straw, at different periods, may be thus stated approximately — 



MOST ECONOMICALLY APPLIED TO THE LAND. 475 

10 cwt. of dry food and straw yield of recent dung 23 to 25 cwt. 

At the end of six weeks 21 cwt. 

After eight weeks 20 cwt. 

When half-roiten 15 to 17 cwt. 

Wlien fully-rotten 10 to 13 " * 

These quantities, you will observe, are supposed to be obtained in 
the common open farm-yards, with the ordinary slow process of fermen- 
tation. An improved, quicker, or more economical mode of fermenting 
the mixed dung and straw may be attended with less loss, and may 
give a larger return of rich and fully-rotten dung. 

A knowledge of these facts shows clearly what is the most economical 
form in which farm-yard manure can be applied to the land. 

1°. The more recent the manure from a given quantity of food and 
straw is ploughed in, the greater the quantity of organic matter we add 
to the land. When the only object to be regarded, therefore, is the gen- 
eral enriching of the soil, this is the most economical and the most ex- 
pedient form of employing farm-yard manure. 

2°. But where the soil is already very light and open, the ploughing 
in of recent manure may make it still more so, and may thus material- 
ly injure its mechanical condition. In such a case the least of two evils 
must be chosen. It may be better husbandry — that is, more economi- 
cal — to allow the manure to ferment and consolidate in the farm-yard 
with the certainty of a considerable loss, than to diminish the solidity of 
the land by ploughing it in in a recent state. 

3°. Again — in the soil, a fermentation and decay similar to that 
which takes place in the farm-yard will slowly ensue. The benefit 
which generally follows from causing this fermentation to take place in 
the field rather than in the open yard is, that the products of the decorn-^ 
position are taken up by the soil, and thus waste is in a great measure 
prevented. But in very light and open soils, this absorption of the pro- 
ducts of decay does not take place so completely. The rains wash out 
some portions, while others escape into the air, and thus by burying the 
recent manure in such soils, less of that waste is prevented which when 
left in the open air it is sure to undergo. It may even happen, in some 
cases, that the waste in such a soil will not be greatly inferior to that 
which necessarily takes place in the farm-yard. The practical man, 
therefore, may question whether, as a general rule, it would not be safer 
in farming very light arable lands, to keep his manure in heaps till it is 
well fermented, and to adopt those means for preventing waste in the 
heaps themselves which science and practical skill point out to him. 

It may be regarded indeed as a prudent general opinion to hold — one, 
however, which must not be maintained in regard to any particular tract 
of land in opposition to the results of enlightened experience— that re- 
cent farm-yard manure {long dung) is not suited to very light soils, 
because it will render them still lighter, and because in them the manure 
may suffer almost as much waste as in the farm-yard ; — and, therefore, 

* In an excellent little practical work printed for private circulation, under the title of 
" Notes on the Culture and Cropping of Arable Land,'' by the late Dr. Coventry, of Edinr 
burgh, the reader will find a valuable section upon manures. The most complete work 
now in exi.stence upon the general subject of asricultural statics, is that of Hlubek, Die Ex- 
ndhrung der Pflanzen und die Slatik des Landbaues. 



40 



« 



476 AFFECTED BY THE PURPOSE IT IS TO SERVE. 



1 



that into such soils it should be ploughed in the compact stale {short 
dung), and as sliort a lime as possible before the sowing of the crop 
which it is intended to benefit. 

4°. But upon loamy and clay soils the contrary practice is recom- 
mended. Such soils will not be injured, they may even be benefitted 
by the opening tendency of the unfermented straw, while at the same 
time the products of its decomposition will be more completely retained 
— the land consequently more enriched, and the future crops more im- 
proved by it. On such soils, the recent dung ploughed in, in the au- 
lunin, has been found greatly more influential upon the crops of corn 
which followed it, either in winter or in spring, than a proportional quan- 
tity of well fermented manure. By such treatment, indeed, the whole 
surface soil is converted into a layer of compost, in which a slow fer- 
mentation proceeds, and which reaches its most fertilizing condition 
when the early spring causes the young corn to seek for larger supplies 
of food. 

5°. But the nature of the crop he is about to raise will also influence 
the skilful farmer in his application of long or short dung to his land. If 
the crop is one which quickly springs up,' runs through a short life, and 
attains an early maturity, he will apply his manure in such an advanced 
state of fermentation as may enable it immediately to benefit the rapidly 
growing plant. In this case, also, it may be better to lose a portion by 
fermenting it in the farm-yard, than, by applying his manure fresh, to 
allow his crop to reach nearly to maturity before any benefit begins to 
be derived from it. 

_ 9°. So also the purpose for which he applies his manure will regulate 
his procedure. In manuring his turnips the farmer has two distinct 
objects in view. He wishes, first, to force the young plants forward so 
rapidly that they may get into the second leaf soon enough to preserve 
them from the ravages of the fly—and afterwards to furntsh them with 
such supplies of food as shall keep them growing till they have attained 
the most profitable size. For the former purpose fermented manure 
appears to be almost indispensable — if that of the farm-yard is employed 
at all—for the latter manure, in the act of slow and prolonged decompo- 
sition, is the most suitable and expedient. 

It is because bone-dust is admirably adapted for both purposes, that 
it has become so favourite a manure in many districts for the turnip 
crop. The gelatine of the outer portion of the bones soon heats, fer- 
ments, and gives off those substances by which the young plant is bene- 
fitted— while the gelatine in the interior of the bone decays, little by lit- 
tle, and during the entire season continues to feed the'ttiaturingbulb. 
Rape-dust, when drilled in, acts in a similar manner, if the soil be suf- 
ficiently moist. It may be doubted, however, whether its effects are so 
permanent as those of bones. 

The considerations I have now presented will satisfy you that the dis- 
putes which have prevailed in regard to the use of long and short dung 

have arisen from not keeping sufficiently distinct the "two questions 

what IS theoretically the best form in which farm-yard dung can be ap- 
plied in general ?— and what is theoretically and practically the best form 
in which it can be applied to this or to that crop, or for this or for that 
special object ? 



TOP-DRESSir^u WITH FERMExNTING MANURES. 477 

§ 18. Of top-dressing with ferment' ng manures. 

If so large a waste occur in the farm-yard where the manure is left 
long to ferment — can it be good husbandry to spread fermenting manure 
as a permanent top-dressing over the surface of the fields ? This, also, 
is a question in regard to which different opinions are entertained by 
practical men. 

That a considerable waste must attend this mode of application there 
can be no doubt. Volatile matters will escape into the air and saline 
substances may be washed away by the rains, and yet there are many 
good practical farmers who consider this mode of applying such manure 
to be in certain cases as profitable as any that can be adopted. Thus — 

1°. It is common in spring to apply such a top-dressing to old pasture 
or meadow lands, and the increased produce of food in the form- of grass 
or hay is believed to be equal, at least, to what would have been ob- 
tained from the same quantity of manure employed in the raising of 
turnips. Where such is really the case experience decides the question, 
and pronounces that notwithstanding the loss which must occur, this 
mode of applying the manure is consistent with good husbandry. But 
if the quantity or market value of the food raised by a ton of manure 
applied in this way is not equal to what it would have raised in turnips 
and corn, then it may as safely be said that the most economical method 
of employing it has not been adopted. 

But theory also throws some interesting light upon this question. 

Old grass lands can only be manured by top-dressings. And if they 
cannot continue, and especially such as are meadowed, to yield an average 
produce, unless there be now and then added to the soil some of those 
same substances which are carried off' in the crop, it appears to be al- 
most necessary that farm-yard dung should now and then be applied in 
some form or other. It is true that hay or straw or long dung contains 
all the elements which the growing grass requires, but if spread on the 
surface of the field and then allowed to ferment and decay, the loss 
would probably be still greater than when, for this purpose, it is collected 
into heaps or strewed in the farm-yard. Thus the usual practice of 
laying on the manure in a highly fermented state may be the most eco- 
nomical. 

2?. Again, where the turnip crop is raised in whole or in part by 
means of bones only, of rape dust, or of other artificial manures, as they 
are called, it is usual to expend a large proportion of the farm-yard dung 
in top-dressing the succeeding crop of clover. Thus the land obtains 
two manurings in the course of the four years' rotation — bones or rape- 
dust with the turnips — and fermented dung with the clover. This second 
application increases the clover crop in some districts one-fourth and the 
after-crop of wheat or barley very considerably also.* 

Here, also, it is clear, that if manure be necessary to the clover, it can 
only be applied in the form of a top-dressing. But why is it necessary, 
as experience says, and why should farm-yard manure, which is known 
to suffer waste, be applied as a lop-dressing rather than rape-dust, which 
in ordinary seasons is not so likely to suffer loss? I offer you the fol- 
lowing explanation : — 

* Such is the case upon some of the farms in the Vale of the Tame (Staffordshire), where 
the turnips are raised wiih rape dust, and wheat follows the clover. 



478 EATING OTF COMPARED WITH GREEN MANURING. 

If you raise your turnip crop by the aid of bones or rape-dust alone, 
you add to the soil what, in most cases, may be sufficient to supply 
nearly all the wants of that crop, but you do not add all which the suc^ 
ceeding crops of corn and clover require. Hence if these crops are to 
be grown continuously, and for a length of time, some other kind of 
manure must be added — in which those necessary substances or kinds of 
food are present which the bones and rape-dust cannot supply. Farm- 
yard manure contains them all. This is within the reach of every 
farmer. It is, in fact, his natural resource in every such difficulty. He 
has tried it upon his clover crop in the circumstances we are considering, 
and has necessarily found it to answer. 

Thus to explain the results at which he has arrived in this special case, 
chemical theory only refers the practical man to the general principle 
upon which all scientific manuring depends — that he must add to the soil 
sufficient sujjplies of every thing he carries off in his crops — and, there- 
fore, without some such dressing as he actually applies to his clover 
crop, he could not long continue to grow good crops of any kind upon 
his land, if he raise his turnips with bones or rape-dust only. 

It might, I think, be worthy of trial, whether the use of the fermented 
dung for the turnips, and of the rape dust for top-dressing the after-crops, 
would not, in the entire rotation, yield a larger and more remunerating 
return. 

§ 19. Of eating off ivith sheep. 

The practical advantages derived from eating ofT turnips and clover 
crops with sheep are mainly of two kinds. Light lands are trodden 
down and solidified, and they are at the same time equably and more 
or less richly manured. With this latter effect, that of manuring, some 
interesting practical facts and theoretical considerations are connected. 
Thus— 

1°. In the preceding lecture (p. 419) I mentioned to you that in 
some parts of Germany, spurry, among other plants, is extensively 
grown, and with much profit, for ploughing in as a green manure. Now 
it is mentioned that the crops of rye which follow a crop of spurry are 
sometimes quite as great when it has been eaten off with sheep or cattle 
as when it has been ploughed in.* 

2*^. In accordance with this statement is the opinion of many skilful 
practical men among ourselves, that a crop of clover or of tares will 
cause a larger after-growth of corn, if it be eaten off with sheep, than if 
it be ploughed in in the green state. 

The correctness of these practical observations appears from a brief 
consideration of one of those interesting theoretical questions we have 
recently been discussing. 

When a crop is eaten off by full-grown animals, it returns again to 
the soil, deprived of a portion of its carbon only (p. 473). The manure 
contains all the nitrogen and saline matter of the green vegetables, and 
in a state in which they are more immediately available to the uses of 
the young plant. Thus far, then, we can understand that in certain 
cases a crop may appear to fertilize the land more after it has been eaten 
and digested, than if it had been ploughed in green, and we can recog- 
nize the correctness of the opinion at which practical men have arrived, 
• y-in Voght, Tiber Munche Vortheile der griiner dungung. 



IMPROVEME?fT OF THE SOIL BY IRRIGATION. 479 

But theory does not forsake us here. As in all other cases in which 
it furnishes a true explanation of known facts, it points to new facts also, 
which more or less modify our received opinions, and define the limits 
within which their truth can be rigorously maintained. Thus — 

1°. Theory says that if the animals fed upon the green crop be in a 
growing state — if they be increasing in muscle or in bone — they will 
not only dissipate through their lungs and skin a portion of its carbon, 
but will retain also a part of its nitrogen and saline matter, and will 
thus return to the soil, in their excretions, a smaller quantity of these 
substances than the crop would have given to it if ploughed in green. 
If, therefore, a maximum fertilizing effect is to be produced upon afield 
by eating off' a green crop, it is not altogether a matter of indifference 
what kind of animals we employ as digesters. 

2°. Again, the practice of green manuring is resorted tochiefly upon 
soils which are poor in organic matter — to which the carbon of ihe green 
crop is of consefjuence, as well as the nitrogen and saline matter it con- 
tains. But when eaten off', much carbon is lost to the soil, and thus the 
supply of organic matter w^hicb it ultimately gets is considerably less 
than if the crop it bore had been ])loughed in in the green state. Such 
soils, then, cannot be equally enriched by the former as by the latter 
method. 

This case presents a very interesting illustration, and one which you 
can readily appreciate, of the kind of useful information which theoreti- 
cal chemistry is capable of imparting upon almost every branch of 
practical agriculture. It says to the farmer — yes, you may in some 
cases, certainly, eat off' the crop with advantage — but if you wish to do 
most good to your land you must eat it off' with fattening, not with grow- 
ing sheep — and you must do so upon soils which are not very poor in 
vegetable matter. And that explains to me also, says the practical man, 
in reply, why I have always found sheep folding to be most beneficial 
on soils which are rich in vegetable matter* (p. 468). 

§ 20. Of the improvement of the soil by irrigation. 

Irrigation, as it is practised in our climate, is only a more refined 
method of manuring the soil. In warm climates, where the parched 
plant would wither and die unless a constant supply of water were ar- 
tificially afforded to it, irrigation may act beneficially by merely yield- 
ing this supply to the growing crops ; but in our latitudes only a small 
part of its beneficial eff'ects can be ascribed to this cause. It is to pas- 
ture and meadow land almost solely that irrigation is applied by British 
farmers, and the good eff'ect it produces is to be explained by a reference 
to various and natural causes. 

1°. If the water be more or less muddy, bearing with it solid matter 
which deposites itself in still places, the good eff'ects which follow its 
diff'usion over the soil may be ascribed to the layer of visible manure 
which it leaves everywhere behind it. Thus the Nile and the Ganges 

* Sprengel explains ttiis fact by alleging that the humic acid of the vegetable matter re- 
tains more effectually the ammonia of the decomposing dnng. There may be something in 
this, but more, in most cases, I think, in the fact that digestion separates much of the carbon 
in which the soils abound, but returns the nitrogen and saline matter almost entirely and in a 
more active state. 



480 THE WATER SHOULD NOT BE STAGNANT. 

fertilize the lands over which their annual floods extend, and partly in 
this way do some of our smaller streams improve the fields over which 
they either naturally flow or are artificially led. 

2°. Or if the water hold in solution, as the liquid manures of the 
farm-yard do, substances on which plants are known fo feed, then to dif- 
fuse them over the surface is a simple act of liquid manuring, from 
which the usual benefits follow. Such is the irrigation which is prac- 
tised in the neigbourhood of our large towns, where the contents of the 
common sewers are discharged into the waters which subsequently 
spread themselves over the fields.* In so far also as any streams can 
be supposed to hold in solution the washings of towns or of higher lands 
— and there are few which are not more or less impregnated in this man- 
ner— so far may their beneficial action, when employed for purposes of 
irrigation, be ascribed to the same cause. 

3°. But spring waters which have run only a short way from their 
source are occasionally found to be valuable irrigators. In such cases, 
also, the good effect may be due in whole or in part to substances held . 
m solution by the water. Thus, in Hme-stone districts, and especially j 
those of the mountain lime-stone formation (Lee. XI., § 8,)— in which ' 
copious springs are not unfrequently met with — the water is generally 
impregnated with much carbonate of lime, which it slowly deposites as 
it flows away froru its source. To irrigate with such water is, in a re- 
fined sense, to lime the land, and at the same time to place within the || 
reach of the growing plants an abundant supply of this substance, in a ' 
form in which it can readily enter into their roots.f 

In other ^districts, again, the springs contain gypsum and common 
salt, an 1 sulphate of soda and sulphate of magnesia, and thus are capa- 
ble of imparting to plants many of those inorganic forms of matter, 
without which, as we have seen, they cannot exhibit a healthy growth. 

4°. Again, it is observed that the good effects of irrigation are produced 
only by running zvater— coarse grasses and marsh plants springing up 
when the water is allowed to stagnate. t This is explained in part by the 
fact that a given quantity of water will soon be deprived of that portion 
of matter held in solution, of which the plants can readily avail them- 
selves, and that when this is the case it can no longer contribute to their 
growth in an equal degree. 

But there is another virtue in running water, which makes it more 
wholesome to the living plant. It comes upon the field charged with 
gaseous matter, with oxygen and nitrogen and carbonic acid, in propor- 
tions very different from those in which these gases are mixed together 
in the air (Lee. II., § 6). To the root, and to the leaf also, it carries 
these gaseous substances. The oxygen is worked up in aiding the de- 
composition of decaying vegetable matter. The carbonic acid is ab- 
sorbed by and feeds the plant. Let the same water remain on the same 
spot, and its supply of these gaseous substances is soon exhausted. In 
its state of rest it re absorbs new portions from the air with comparative 
slowness. But let it flow along the surface of the field, exposing every 

For an interesting account of the eflFects of such irrigation in the neighbourhood of Edin- 
burgh, see Stephens, On Irrigation and Draining, p. 75. 

t Some of the water used in the well-known scientific irrigations at Closeburn Hall, in 
Dumfries shire, appears to have been impregnated with lime. See Stephens, p. 43. 

X Low's Elements of Agriculture^ 3d edition, p. 472. 



A GOOD DRAINAGE NECESSARY. 481 

moment new particles to the moving air, and it taltes in the carbonic 
acid especially with much rapidity — and as it takes it from the air, al- 
most as readily again gives it up to the leaf or root with which it first 
comes into contact. This is no doubt one of the more important of the 
several purposes which we can understand running water to serve when 
used for irrigation. 

But further, if water be allowed to stagnate over the finer grasses, 
they soon find themselves in circumstances in which it is not consistent 
with their nature to exhibit a healthy growth. They droop, therefore, 
and die, and are succeeded by new races, to which the wet land is more 
congenial. 

6°. It is known also, that even running water, if kept flowing with- 
out intermission for too long a period, will injure the pasture. This is 
because a long immersion in water induces a decay of vegetable matter 
in the soil which is unfavourable to the growth of the grasses — produ- 
cing chemical compounds which are not naturally formed in those situ- 
ations in which the grasses delight to grow, and which are unwholesome 
to them. Although, therefore, the water continues to supply those va- 
rious kinds of food by which the grasses are benefitted, yet it becomes 
necessary to withdraw it for a time in order that other injurious conse- 
quences iTiay be avoided. 

6°. Lastly. — Irrigation is most beneficial where the land is well 
drained beneath — where the water, after the irrigation is stopped, can 
sink and find a ready outlet. The same benefits indeed flow from the 
draining of irrigated as from that of arable lands. The soil and subsoil 
are at once washed free of any noxious substances they may naturally 
contain, or may have derived from the crops they have grown, and are 
manured and opened up by the water which passes through them. As 
the water descends also, the air follows it, to change and mellow the 
under-soil itself. 

Such are the main principles upon which the beneficial action of irri- 
gation depends, and they appear to me satisfactorily to account for all 
the facts upon the subject with which I am acquainted. I pass over the 
alleged beneficial action of water in keeping the temperature of irriga- 
ted fields from sinking too low. As irrigation is practised incur islands, 
little of the good done to watered meadows can be properly attributed to 
this cause. 



I have now drawn your attention to the most important and readily 
available means, mechanical and chemical, for improving the soil. 
Let us next study the products of the soil — their composition, their 
differences, and the purposes they are intended to serve in the feeding 
and nourishment of animals. 



LECTURES 

ON THE 

APPLICATIONS OF CHEMISTRY AND GEOLOGY 

TO 

AGRICULTURE. 

ON THE PRODUCTS OF THE SOIL, AND THEIR 
USE IN THE FEEDING OF ANIMALS. 



.1^ 



CONTENTS. 



FART XV. 

ON THE PRODUCTS OF THE SOIL, AND THEIR USE IN THE FEEDING 

OF ANIMALS. 



LECTURE XIX. 

OP THE PRODUCE OF THE SOIL. 



Of the maximum or greatest possible and 
the average or actual produce of tlie 

land p. 487 

Of tiie circumstances by which the pro- 
duce of food is affected — climate, sea- 
son, soil, «fcc 4S8 

Influence on the mode of culture on the 

produce of food 490 

Of the theory of the rotation of crops. . .. 492 

Why land becomes tired of clover 494 

Of the theory of fallows 495 

Of wheat and wheaten flour 498 

Of the composition of wheaten flour. . . . 499 
Of the influence of soil and climate on 

the composition of wheaten flour 501 

Inflnence of variety of seed, of mode of 
culture, oftimeof cutting, and of special 
manures on the composition of wheat. 502 
Of the effects of germination and of bak- 
ing upon the flour of wheat 504 

Of the supposed relation between the per- 
centage of gluten in flour, and the 

weight of bread obtained from it 507 

Of the composition of barley, and the in- 
fluence of different manures upon the 
relative proportions of its several con- 
stituents 508 

Effect of malting upon barley 509 

Of the composition of oats, and effect of 
manures in modifying that composition. 510 



Of the composition of rye, and the effect 
of different manures upon its composi- 
tion p. 510 

Composition of rice, Indihn com, and 
buck-wheat 511 

On the alleged general effect of different 
manures in modifying the amount of 
gluten and albumen in wheat, barley, 
oats, and rye 513 

Composition of peas, beans, and vetches. 515 

Effect of soils and manures on the quality 
of peas and beans 518 

Of the composition of potatoes, and the 
effect of circumstances in modifying 
their composition 520 

Of ihe composition of the turnip, the car- 
rot, the beet, and 'Jie parsnip 523 

Of the composition of the gieen stems of 
peas, vetches, clover, spurry, and 
buck-wheat 525 

Of the composition of the grasses when 
made into hay 526 

Of hemp, hne, rape, and other oil-bearing 
seeds 528 

General differences in composition among 
the different kinds of vegetable food. . . 529 

Average composition and produce of nu- 
tritive matter per acre, by each of the 
usually cultivated crops S30 



LECTURE XX. 

OF MILK AND ITS PRODUCTS. 



Of the properties and composition of 
milk 533 

Of the circumstances by which the com- 
position or quality of milk is modified. 534 

Of the circumstances which affect the 
quantity of the milk.. 540 

Of the mode of separating and estimating 
the several constituents of milk 542 

Of the sugar of milk, and of ihe acid of 
milk or lactic acid 543 

Of the mutual relations which exist be- 
tween lactic acid and the cane, grape, 
and milk sugars 544 

Of the souring and preserving of milk. .. 546 



Of the separation and measurement of 
cream — the galactometer — the compo- 
sition of cream, and the preparation of 
cream cheese 547 

Of the separation of butter by churning 
or otherwise 549 

Of the composition of butter 551 

Of the average quantity of butter yielded 
by milk and cream, and of the yearly 
produce of a cow 552 

Of the circumstances which affect the 
quality of butter 553 

Of the fatty substances of which butter 
consists, and of the acid of butter (buty- 



486 



CONTENTS OF PART IV. 



ric acid), and the capric and caproic 

acids p. 557 

Of casein or the curd of milk eind its pro- 
perties 561 

Of the relations of casein to the sugars 

and fats 562 

Of the rancidity smd preservation of butter 563 
Of the natural and artificial curdling of 

milk 566 

Of the preparation of rennet 567 

Theory of the action of "rennet 569 

Of the circumstances by which the quali- 
ty of cheese is affected , 573 

Circumstances under which cheese of 
different qualities may be obtained from 
the same milk 575 



Of the average quantity of cheese yielded 
by different varieties of milk, and of 
the produce of a single cow ..p. 580 

Of the fermented liquor from milk, and of 
milk vinegar 581 

Of the composition of the saline constitu- 
ents of milk ib. 

Purposes served by milk in the animal 
economy 582 

On the churning of milk in the French 
chum ib. 

Quantity of milk eQid butter yielded by 
Ayrshire cows 583 

Profit of making butter and cheese com- 
pared with that of selling the milk 581 



LECTURE XXL 

OF THE FEEDING OF ANIMALS, AND THE PURPOSES SERVED BY THE FOOD. j 

Kind and quantity of additional food re- 
quired by a pregnant animal 604 

Kind and quantity of additional food re- 
quired by a milking animal 605 1 

Influence of size, condition, warmth, ex- I 
ercise, and ligtit on the quantity of food 
necessary to make up for the natural 
waste 607 

Influence of the form or state in which 
the food is given on the quantity re- 
quired by an animal 611 

Influence of soil and culture on the nutri- 
tive value of agricultural produce 612 

Can we correctly estimate the feeding 
properties of different kinds of produce 
under all circumstances'?. .». ...»..., 613 

Effect of different modes of feeding on 
the manure and on the soil 615 

Summary of the views illustrated in this 
lecture 617 

Concluding section , 619 



Of the substances of which the parts of 
animals consist 586 

Whence does the body obtain these sub- 
stances? are they contained in the 
food? 589 

Of the respiration of animals, and of the 
purposes served by the starch, gum, 
and sugar contained in vegetable food. . 591 

Of the origin and purposes served by the 
fat of animals 594 

Of the natural waste of the parts of the 
body in a fuU grown animal 597 

Of the kind and quantity of food necessa- 
ry to make up for the natural waste in 
the body of a full-grown animal 

The health of an animal can be sustained 
only by a mixed food 

Of the kind and quantity of additional 
food required by the fattening animal.. 

Kind and quantity of additional food re- 
quired by a growing animal 602 



598 
COO 
601 



LECTURE XIX. 

Of the produce of the soil,— Average produce of England and Scotland.— Circumstances by 
which the produce of the land is affected.— Iniluence of climate, of season, of soil, of thi; 
kind and variety of crop, of the method.of culture, and of the course of cropping. — Theory 
of the rotation of crops. — Why lands become tired of clover (clover-sick) and other special 
crops-— Theory of fallows.— Composition of wheat, oats, barley, rye, and Indian corn.— In- 
fluence of climate, soil, manure, variety of seed, mode of culture, and time of cutting, upon 
the composition ofthese grains. — Effect of baking upon bread. — Supposed relation between 
the weight of bread and the proportion of gluten.— Effect of germination (maltmg) upon 
barley. — Composition of peas, beans, and vetches. — Effects of soil, &c., upon the boiling 
quality of peas. — Composition of the turnip, the carrot, the beet, and the potatoe. — Effect 
of soil, age, size, rapidity^of growth, <fcc.,upon their composition. — Relative proportions of 
nutritive matter produced by different crops on the same extent of ground. — Composition 
of the grasses and clovers. — Effect of soils, manures, time of cutting, mode of drying, &c., 
upon their composition and nutritive value. 

Having now considered the most important of those means by which 
the soil may be improved, it will be proper to direct our attention to that 
which the land produces — to the chemical nature of the crops you raise, 
to the differences which exist among them, and to the purposes they are 
fitted to serve in the feeding of man and other animals. 

Agricultural products are of three distinct kinds : 

1°. Such as are directly reaped from the soil in the form of corn, pota- 
toes, hay, &c. 

2°. Such as are the result of a kind of natural process of manufacture, 
by which the direct produce of the soil is more economically converted 
into the beef and mutton of the feeder of stock. 

3°. Such as are the results of a further conversion at the hands of the 
dairy farmer, and are sent to market in the form of butter and cheese. 

Thus three distinct topics of consideration present themselves in con- 
nection with the produce of the soil, — the nature of the immediate pro- 
ducts themselves — the economy of the feeding of stock — and the prepara- 
tion of butter and cheese. We shall study these several topics in their 
natural order. 

§ 1. Of the maximum or greatest possible, and the average or actual^ 
produce of the land. 

There is a wide difference in most countries between the actual 
amount of food produced by the land, and that which, in the most fa- 
vourable circumstances, it would delight to yield. 

An imperial acre of land in our island has been known to yield of 
wheat 70 bushels,* barley 80 bushels, oats 100 bushels, potatoes 30 
tons,f and turnips 60 tons.J 

The average produce of the land, however, is far below these quanti- 
ties. It is not easy to arrive at a tolerable approximation even to the 

• In'the county of Middlesex the produce of wheat varies from 12 to 68bushels— of bar- 
ley from 15 to 75— and of oats from 32 to 96 ^xxsheis.—Middleton's View of the Agricul- 
ture of Middlesex, 1798, pp. 176, 183, and 188. 

t See Mr. Fleming's experiments upon potatoes in the Appendix. 

X Perhaps this is not the maximum.— \x).i\\& Second Report of the Royal Agricultural Im 
provement Society of Ireland, p. 57, a crop of turnips is mentioned, which weighed 56 tons- 
tops and bulbs amounting together to 76 tons. 



488 PRODUCE OF THE LAND IN GREAT BRITAIN. 

true average produce of the island. Mr. Macculloch estimates that o^ 

wheat at 26 bushels an acre, barley at 32, and oats at 36. 

Sir Charles Lemon gives for the average produce of all England, and 

for the highest and lowest county averages, the following numbers 

Average for Highest Lowest 

all i^ngland county average county average 

in bushels. in bushels. in bushels. 

Wheat - - . 21 26 Nottinghamshire. 16 Dorset. 

Barley - - - 321 40 Huntingdon. 24 Devon. 

Oats - - - . 351 48 Lincolnshire. 20 Gloucester. 

Potatoes - - - 241 360 Cheshire. 100 Durham. ^ 

While in Scotland, according to Mr. Dudgeon, the average produce 
of corn IS — • 

,.,7., Good land. Lifter land. 

Wheat - - - - 30 to 32 bushels. 22 to 26 bushels. 
Barley - - - - 40 to 44 do. 34 to 38 do. 

Oats 46 to 50 do. 36 to 43 do. 

If these numbers of Sir Charles Lemon and of Mr. Dudgeon are to be 



luce 1 1 



depended upon, the averages for the whole island cannot be far from ii 
wheat 24 bushels, barley 34 bushels, oats 37 bushels, potatoes 6 tons, I' 
and^ turnips 10 tons. I 



Though even these, especially in regard to the root crops, must be 
considered as in a considerable degree hypothetical.* 

What^ is the cause of the striking differences above exhibited between 
the maximum produce of certain parts of the island and the average pro- 
duce of the whole ? Are such differences necessary and unavoidable ? 
Can the less productive lands not be made to yield a larger return ? 
Can the large crops of the richer districts not be further increased, and 
their amount kept up for an indefinite succession of seasons ? 

These interesting questions lie at the foundation of all agricultural im- 
provement—and skill and science answer that, though differences to 
a certain amount are unavoidable, yet that means are already known 
by which the fertility of the richer 'lands may be maintained, and the 
crops of the less productive indefinitely enlarged. 

§ 2. Of the circumstances by which the produce of food is affected 

climate, season, soil, ^r. 

The quantity of food produced by a given extent of land is affected by 
the chmale, by the season, by the soil, by the nature of the crop, by the 
variety sown or planted, by the general method of culture, and by the ro- 
tation or course of cropping that is adopted. 

1°. Climate. — That the warmth of the chmate, the length of the sum- 
mer, and the quantity of rain that falls, influence in a remarkable degree 
the amount of food which a district of country is fitted to raise, is" fa- 
miliar to every one. The warmth of tlie equatorial regions maintains a 
perpetual verdure, while the short northern summers aflbrd only a few 
months of pasture to the stunted cattle. The difference of latitude be- 
tween the extreme ends of our island produces a similar difference, though 
in a less degree. The almost perennial verdure of the southern counties 

* In 1821, Mr. Wakefield estimated the average produce of wheat in all England at 17 
bushels only—Devonshire producing an average of 20, and the lands near the coast of Kent. 
Norfolk; Suffolk, and Essex, 40 bushels per acre. 



INFLUENCE OF CLIMATE, SEASON, AND SOIL. 489 

cannot be hoped for in the north of Scotland, and yet it is said that in 
parts of Ross-shire the com and turnip crops are equal to those of the 
most favoured districts of Britain. Is this to be regarded solely as the 
triumph of skill and industry over the difficulties presented by nature ? 

2°. Season. — The influence of the seasons, wet or dry, warm or cold, 
has been observed by the farmer in all ages, and it cannot be entirely 
overcome. The heavy crop of this year may not be reaped again on 
the next, because an unusual cold may arrest its growth. And 
yet good husbandry will do much even here — since the higher the farm- 
ing the fewer the number of failures which the intelligent man will 
have occasion to lament. 

3°. Soil. — Diversity of soil is held to be a sufficient reason for differ- 
ence both in kind and in weight of crop. A poor sand is not expected to 
give the same return as a rich clay. Yet in regard to the capabilities of 
soils under skilful management, practical agriculture appears as yet to 
have much to learn. Is there any method hitherto little tried by which 
soils of known poverty may be compendiously and cheaply doctored, so 
as to produce a greatly larger return ? Science seems to say that there is, 
and points to a wide field of experimental research, by the diligent cul- 
ture of which we may hope that this great result will hereafter be at- ' 
tained. The principles upon which this hope rests have been explained, 
for the most part, in the preceding Lectures. 

4°. Kind of crop. — The amount of food, either for man or beast, 
which a given field will produce, depends considerably upon the kind 
of crop which is raised. Thus a crop of 30 bushels of wheat will yield 
only about 1400 lbs. of fine flour, while a crop of 6 tons of potatoes will 
give about 4400 lbs. of an agreeable, diy, and mealy food. Thus the 
gross weight of food for man is in the one case three times what it is in 
the other. So it is said, on the authority of the Board of Agriculture, 
that a crop of clover, of tares, of rape, of potatoes, turnips, or cabbages, 
will furnish at least thrice as much food for cattle as one of pasture grass 
of medium quality.* 

5°. Variety of seed sown. — The variety of seed sown has also an im- 
portant influence on the amount of produce reaped. I need not refer to 
the well known necessity of changing the seed if the same land is to 
continue to yield good crops — but of strange seeds of the same species 
two varieties will often yield very unlike weights of corn, of turnips, or 
of potatoes. I may quote as an illustration the experiments of Colonel 
Le Couteur upon wheat. He found, on the same soil and under the 
same treatment, that the varieties known by the name of the "White 
Downy and the Jersey Dantzic yielded respectively : 

Grain, Weight pr bush. Straw. Fine flour. Fine do. pr.ct. 

White Downy - 48 bush. 62 lbs. 45-57 lbs. 2402 lbs. 80flbs. 
Jersey Dantzic - 43| bush. 63 lbs. 4681 lbs. 2161 lbs. 79flbs. 

while on a different soil and treated differently from the above, two other 
varieties yielded — 

Grain. Weight pr bush. Straw. Fine flour. Fine do. pr.ct 
Whittington, - - - 33 bush. 61 lbs. 7786 lbs. 1454 lbs. 72^ lbs. 
BelleVue Talavera, -52 bush. 61 lbs. 5480 lbs. 2485 lbs. f 781 lbs. 

• Loudon's Encyclopedia of Agriculture, p. 910. 

t Journal of the Royal Agricultural Society of England, L, p. 123, 



490 



INFLUENCE OP THE METHOD OF CULTURE, 



In each of these cases, therefore, and especially in the last, a striking 
difference presented itself both in the absolve and in the relative wethi 
of gram and of straw reaped under precisely similar circumstances, by 
the use of different varieties of the same species of seed. Nor are the 
above by any means extreme cases. In the same field I have known 
the Golden If ent and the Flanders Red varieties, sown in the same 
spring to thrive so differently, that, while the former was an excellent 
crop, the latter was almost a total failure. It will require a very refined 
chemistry to explain the cause of such diversities as these. 

§ 3. Influence of the method of culture upon the produce of food. 
In addition to the circumstances above alluded to, the quantity of food i^ 
tiiat IS raised depends very much upon the method of culture which is 
llT^. /i""^' •" '^"v,*"^ medium quality, our opinion in regard to the 
quantity of food it is likely to yield would be greatly affecfed by the 
answers we should obtain to the following questions ;— 
Air / f* ^^^ ^^^^ in permanent pasture, or is it under the plough ?— 
With the exception of rich pasture, it is said that land, under clover or 
turnips, will produce three times as much for cattle as when under grass 
n such a green crop then alternate with one of corn, the land would 
every two years produce as much food for stock as it would during three 
years if lying in grass, besides the crop of corn as food for man, and 
of straw for the production of manure. 

This statement may possibly be a little exaggerated, or may represent tru- 
ly the comparative produce of food in special cases only—yet there seems 
sufficient reason for beheving, as a general rule, that a very much larger 
amount of food may be reaped from land under arable "culture, than 
wnen J aid away to permanent pasture. 

2°. What kind and quality of inanure is applied ?— Every practical 
man knows the importance of manuring his land, and how much tlie 
abundance of every crop he sowsdepends both upon the quantity and upon 
the kind of manure he is able to add to it. i J P^^^ 

3°. In what way is it applied ?-~But much depends also upon the 
manner m which the manure is expended, or the kind of crop to which 
it IS applied. ^ 

I have already (p. 477) directed your attention to the loss which must 
necessanly be sustained by top-dressing with farm-yard manure, and yet 
how in certain modes of cropping and manuring the land, it may be 
not on y advisable but necessary to do so. Yet the comparative return 
of food obtained from the use of such manure, when applied a^ a top- 
dressing to grass land for instance, and when buried with the turnip crop 
in the usual manner, is very unlike. 

Thus, suppose an acre of grass land, of such a quality as to produce 
annually without manure Ij tons of hay, to be top-dressed every spring 
or autumn with 5 tons of farm-yard manure per acre— and suppose 
anotlier acre of the same land in arable culture to be manured for turnips 
with 20 tons of farm-yard manure at once. Then the grass land, by 
tJie aid of the manure, would not produce more than double its natural 
crop, or 21 tons an acre, that is, 10 tons of hay in the four years. This I 
behove IS making a large allowance for the efl^ect of the manure. 

Hut the arable land, in the four years, if of the same quality, may be 



AND OF THE MOEE OF APfijlING THE MANURE. 491 

expected to produce — turnips 20 tons, barley 36 bushels, clover 2| tons, 
wheat 28 bushels ; besides upwards of 4 tons of straw. 

In all these taken together there must be much more food than in the 
ten tons of hay. 

If we consider the money profit, however, to the farmer, the result 
may be different. The cost of raising the ten tons of hay, exclusive of 
rent, may be reckoned at one-half the produce, and of the several crops 
in the four years' rotation at three-quarters of the produce: we thus 
have for the clear return — 

In the one case, half the produce — 5 tons of hay ; 
In the other case, a fourth of the produce — 5 tons of turnips, 9 bushels 
of barley, i ton of clover, 7 bushels of wheat, and 1 ton of straw. 

Let the clover and the straw together equal in value only one ton of 
the hay, and the money value in the two cases will stand as follows ;— 
Hay, 4 tons, at c£5, = 6€20 

Turnips, 5 tons, at 10s. = c€2 10 
Barley, 9 bush., at 4s. = 1 16 
Wheat, 7 bush., at 7s. =-2 9 

6 15 



Leaving a gain upon the grass land of d£l3 5 
Or, 6£3. 6s. an acre every year. 

Thus, though more food is raised by converting the land to arable 
purposes, and more people may be sustained by it, yet more money 
may be made by meadowing the land — where a ready market exists 
for the hay, lohere it is allowed to he sold off the farm, and where abun- 
dance of manure can he ohtained for the ^jurjjose of top-dressing the grass 
every year. It is only in the neighbourhood of large towns, however, 
that all these circumstances usually co-exist, and hence one cause of the 
value of grass land in such localities. 

The farmer, however, is never prohibited from selling his corn off the 
farm, or his fat stock, or his dairy produce, and thus at a distance from 
large towns he must turn his attention solely to the raising of one or other 
of these kinds of produce. 

Of the two ways of employing his grass or green crops — in rearing 
and fattening cattle, namely, and in the production of butter and cheese 
— we shall hereafter see reason to believe that theoretically the latter 
ought both to be the most profitable in money to the farmer, and at the 
same time to produce the greatest amount of food for man. 

3°. W hat rotation or course of cropping is adopted? — If the land be 
cropped with corn, year after year, the produce of food will not only be, 
less than if an alternate husbandry were introduced — but the yearly return 
of corn, even on the richest land, must sooner or later diminish, till at 
length the crop will not be sufficient to defray the expense of cultivation. 
The tillage of such land must then be abandoned, and it must be left to 
a slow process of natural restoration. No arable land will produce so 
much food if year by year it be made to raise the same crop, as if the 
crop be varied — and especially as if corn, root, and leguminous crops be 
made to succeed each other in a skilful alternation. 

Upon the introduction of the alternate husbandry, it was found that 
upon lands formerly in pasture, not only could one-third more stock be 



492 THEORY OF THE ROTATION OF CROPS. 

kept continuously than before, but that in addition a crop of corn could be 
reaped every second year. On the other hand, those which had been 
cropped with corn alone, or which after two white crops had usually been 
left to nalved fallow, yielded more corn in a given number of years than 
before, while a green crop every second year was raised on them besides. 
It cannot be doubted, therefore, that a change of cropping influences, in 
a great degree, the amount of food wMch tlie same piece of land is fitted 
to produce. 

§ 4. Of the theory of the rotation of crops. 

Upon what principles do the beneficial effects of tliis change of crop- 
ping depend ? What is the true theory of a rotation of crops ? 

It was supposed by Decandolle — 

1°. That the roots of all plants gave out or excreted certain substan- 
ces peculiar to themselves — and, 

2°. That these substances were unfavourable to the growth of those 
plants from the roots of which they came, but were capable of promo- 
ting the growth of plants of other species — that the excretions of one 
species were poisonous to itself, but nutritive to other species. 

Upon these suppositions he explained in a beautiful and apparently 
simple and convincing manner the beneficial effects of a rotation or al- 
ternation of different crops. If wheat refused to grow after wheat, it was 
because the first crop had poisoned the land to plants of its own kind. 
If after an interv^ening naked fallow a second wheat crop could be safely 
grown, it was because during the year of rest the poisonous matter had 
lime to decompose and become again fitted to feed the new crop. And 
if, after beans or turnips, wheat grew well, it was because the excretions of 
these plants were agreeable to the young wheat, and fitted to promote 
its growth. 

Thus easily explained were the benefits both of a rotation of crops 
and of naked and other fallows — and supported at once by its own beauty 
and by the great name of Decandolle, this explanation obtained for 
many years an almost universal reception. 

But though there seems reason enough for believing (p. 82) that the 
roots of plants really do give out certain substances into the soil — there is 
no evidence that these excretions take place to the extent which the 
theory of Decandolle would imply — none of a satisfactory kind that 
they are noxious to the plants from which they are excreted* — and none 
that they are especially nutritive to plants of other species. Being un- 
supported by decisive facts and observations therefore, the hypothesis of 
Decandolle must, for the present, be in a great measure laid aside, and we 
must look to some other quarter for a more satisfactory theory of rotation. 

The true general reason why a second or third crop of the same kind 
will not grow well, is — not that the soil contains too much of any, but that 
it contains too little of one or more kinds of matter. If, after manuring, 
turnips grow luxuriantly, it is because the soil has been enriched with 
all that the crop requires. If a healthy barley crop follow the turnips, 
it is because the soil still contains all the food of this new plant. If 
clover thrive after this, it is because it naturally requires certain other 
kinds of nourishment which neither of the former crops has exhausted. 
If, again, luxuriant wheat succeeds, it is because the soil abounds still in 

* See pa^e 81, not«. 



PRACTICAL RULES SUGGESTED BY THEORY. 493 

all that the wheat crop needs — the failing vegetable and other matters of 
the surface being increased and renewed by the enriching roots of the 
preceding clover. And if now, turnips refuse again to give a fair re- 
turn, it is because you have not added to the soil a fresh supply of that 
manure without which they cannot thrive. Add the manure, and the 
same rotation of crops may again ensue. 

We have already had freqiient occasion, in studying the inorganic 
constituents of plants, to observe that diflferent species rec^uire very un- 
like proportions of the several kinds of inorganic food which they derive 
from the soil. Some require a large proportion of one kind, some of 
another kind. If a soil, therefore, abound especially in one of these va- 
rieties of inorganic food, one kind of plant will especially flourish upon 
it — while, if it be greatly deficient in another substance, a second plant 
will remarkably languish upon it. If it abound in both substances, then 
either crop will succeed which we may choose to sov\^, or they may be 
alternately cultivated with a fair return from each. 

Upon this principle the true general explanation of the benefit of a 
rotation of crops appears to depend. There may be special cases in 
which pecuUar qualities of soil or climate may intervene and give rise 
to appearances, or cause results to which this principle does not apply, 
but for the general practice it seems to afford a satisfactory explanation. 

It may be said that this explanation seems to imply that the same 
kind of crop maybe reaped from the same soil for an indefinite number of 
years, by simply adding to it what the crop carries off'. This is certain- 
ly implied in the principle — and if we knew exactly what to add for each 
crop, we might possibly attain this result, except in cases where the soil 
undergoes some gradual chemical alteration within itself, which it may 
require a change of treatment to couuteract. At all events it does not 
seem impossible to obtain crop after crop of the same kind — and we may 
hope hereafter not only to be able to effect this, but to do it in a suffi- 
ciently economical manner. 

Two practical rules are suggested by the fact that different plants require 
different substances to abound in a soil in which they shall be capable of 
flourishing. 

1°. To grow alternately as many different classes or families of plants 
as possible — repeating each class at the greatest convenient distance of time. 

In this country we grow chiefly root crops, — corn plants ripened for 
seed, — leguminous plants sometimes for seed (peas and beans), and 
sometimes for hay or fodder (clover and tares), — and grasses, and these 
in alternate years. Every four, five, or six years, therefore, the culture 
of the same class of plants comes round again, and a demand is made 
upon the soil for the same kinds of food in the same proportion. 

In other countries — tobacco — flax — rape, poppy or madia, cultivated for 
their oily seeds — or beet for its sugar, can be cultivated with profit, and 
being interposed among the other crops, they -make the return of each 
class of plants more distant. A perfect rotation would include all those 
classes of plants which the soil, cUmate, and other circumstances allow 
to be cultivated with a profit. 

2°. A second rule is to repeat the same species of plant at the greatest 
convenient distance of time. In corn crops there is not much choice, 
since in a four years' course two corn crops, out of the three (barley, 



494 WHV LAND BECOMES CLOVER-SICK. 

wheat, oats) usually grown, must be raised. But of the leguminous 
crops we have the choice of beans, peas, vetches, and clover — of root 
crops, turnips, carrots, beets, and potatoes — while of grasses, there is a 
great variety. Instead, therefore, of a constant repetition of the turnip 
(5very four years, theory says — make the carrot or the potatoe take its 
place now and then, and instead of perpetual clover, let tares or beans, 
or peas, occasionally succeed to your crops of corn. The land loves a 
change of crop, because it is better prepared with that food which the 
new crop will relish, than with such as the plant it has long fed before 
continues to require. 

It is for this reason that new species of crop, or new varieties, when 
first introduced, succeed remarkably for a time, and give great and en- 
couraging returns. But they are continued too long — till the soil has 
been exhausted in some degree of those substances in which the new 
crops delighted. They cease in consequence to yield as before, and fall 
into undeserved disrepute. Give them a proper place in a long rotation, 
aud tliey will not disappoint you. 

It is constant variety of crops, which, with rich manuring, makes our 
market gardens so productive — and it is the possibility of growing in the 
fields many different crops in succession, that gives the fertihty of a gar- 
den to parts of Italy, Flanders, and China.* 

§ 5. Why land becomes tired of clover {clover-sick). 

What I have said of the general principle might be supposed to 
explain fully why crops fail at one time and succeed at another — why 
the soil will nourish one plant well, while it is unable adequately to sus- 
tain another. But a brief reference to the case of tlie clover plant will 
enable us to see how modes of culture, apparently skilful and generous, 
may yet be of such a kind as to lead, sooner or later, to the inevitable 
failure of a particular crop. 

It is known that upon many well cultivated farms the lands become 
now and then tired or sick of clover, and this crop failing, the wheat 
which succeeds it in a great measure fails also. It may be said that the 
soil in such a case is in want of something, and so it is, — but how does 
this deficiency of supply arise ? The land is skilfully managed and 
has been well manured, and the failure of the clover crop is, therefore, a 
matter of surprise. 

If farm-yard manure be copiously applied previous to the root crop, 
the land has received a certain more or less abundant return of all those 
substances which the last rotation of crops had carried off from, it, — and 
which the new rotation will require for food. When the clover comes 
round, therefore, a supply of proper food is ready for it, as well as for 
the wheat which is to follow. 

But if ihe turnip crop be raised by means of bones only, the lime 

* A method of superseding in some measure the necessity of a rotation of crops is de- 
scribed by Mr. James Wilson as long practised in Shetland, in the neighbourhood of Ler- 
wick. " It is known that bear has been grown in the same patch for perhaps 100 years suc- 
cessively, and this they managed by scarifying other parts of the ground (the out-field por- 
tion), and renovating the arable patch by spreading it over the surface." This was varying 
the soil instead of the crop. A five years' rotation, however, is now getting into favour, and 
the average produce, after liming, is found to be uicreased by it four-fold. In this district 
much herring refuse is employed as a manure, and the improved land lets at 203. an acre. 
— Wilson's Voyage round the Coast oj Scotland, II., p. 268. • 



RESULT OF FREQUENT MANURING WITH BONES. 495 

and phosphoric acid which the earth of bones contains are almost the only 
kinds of inorganic food required by plants that are returned to the soil. 
By the aid of the animal matter and the small supply of other substances 
in the bones,* good crops — and especially the turnips and tlie corn which 
immediately follows them — may be raised for a few rotations, but at 
every return the clover and wheat will become more unhealthy, till they 
at length appear to sicken upon the land. Neither bones nor rape-dust 
nor any such single substance can replace farm-yard manure for an in- 
definite period, because it does not contain all the substances which the 
entire rotation of crops requires. 

If wood-ashes be used along with the bones, the bad effects I have des- 
cribed will be much longer delayed — they may even be delayed indefi- 
nitely, since wood-ashes are said to be especially favourable to the growth 
of clover and other leguminous plants, (p. 353), and this because they 
contain those substances which the clovers require. 

It thus appears, therefore, that while the failure, upon a given spot, of 
a crop which formerly grew well there, is explained generally upon the 
principle that the soil has become deficient in something which the crop 
requires — the cause of this deficiency may not unfrequently be found in 
the mode of culture, or in the species of manuring which the land has 
received. The cause being discovered, the remedy is easy. Cease to 
employ exclusively the manure with which your land has hitherto been 
dressed. Mix your bones or rape-dust with wood-ashes, with gypsum, 
or with other portable manures in which the necessary food of your 
crops is present — or employ farm-yard manure now and then in their 
stead, and you will apply the most likely remedy. Unless this be done, 
it will be of comparatively little service to vary the species, — to substi- 
tute tares or beans for the clover, — since these also will refuse to grow 
while the same incorrect system of manuring is persisted in. 

I have already drawn your attention (p. 477) to the falling of the 
clover crops in certain parts of Staffordshire, where the turnips are 
raised by means of rape-dust — and of the mode of improving them by a 
top-dressing of farm-yard manure. Were this manure laid in with the 
turnips, the after top-dressing would most probably not be required. 

§ 6. Of the theory of fallows. 

By fallowing, it has been known in all ages that the produce of the 
land was capable of being increased. How is this increase to be ac- 
counted for ? We speak of leaving the land to rest, but it can never 
really become wearied of bearing crops. It cannot, through fatigue, lie 
in need of repose. In what, then, does the efficacy of naked fallowing 
consist ? 

1°. In strong clay lands one great benefit derived from a naked fallow 
is the opportunity it affords for keeping the land clean. In such soils it 
is believed by many that weeds cannot possibly be extirpated without an 
occasional fallow. It is certain that naked fallows are had recourse to 
in many places for the purpose of cleaning the land, where if it could 
easily have been kept so by other means they would not have been 
adopted. Is it not the case on some farms that a neglect of other avail- 
able methods of extirpating weeds has rendered necessary the assistance 
* For the enmpositiort of bonee, eee page 446. 



496 FALLOWS MAY REPLACE DEEP PLOUGHINQ AND DRAINING. 

of a naked fallow, while on similar farms in the same neighbourhood 
they can easily be dispensed with ? 

2°. In a naked fallow, where the seeds are allowed to sprout, and 
young plants to shoot up, which are afterwards ploughed in, the land is 
enriched by a green manuring of greater or less extent. If weeds abound, 
the enriching is the greater — if they are more scanty, it is less — ^but in 
almost every instance where land lies without an artificial crop during 
the whole summer, a crop of natural herbage springs up, the burying of 
which in the soil must be productive of considerable good. 

3°. When land is assiduously cropped, the surface in which the roots 
chiefly extend themselves becomes especially exhausted. In indiffer- 
ently worked land some parts of this surface may be more exhausted than 
others. By leaving such soils to themselves, the rains that fall and more 
or less circulate tlirough them equalize the condition of the whole sur- 
face soil — in so far as the soluble substances ii contains are concerned. 
The water also, which in dry weather ascends from beneath, brings 
with it saline and other soluble compounds, and imparts them to the up- 
per layers of the soil. Thus, by Ijang fallow, the land, becomes equa- 
bly furnished over its whole surface with all those substances required by 
plants which are anywhere to be found in it. The roots of the crop, 
therefore, can more readily procure them, and thus the plants more 
readily and more quickly grow. In some cases, this beneficial action of 
the naked fallow loill, to a certain extent, make up for shallow ploughing , 
and for insufficient working of the land, 

4°. It is known that the subsoil in many places is of such a nature 
that it must be turned up to the surface, and exposed for a considerable 
period to the action of the air, before it can be safely mixed witli the sur- 
face soil. To a less degree stiff clay lands acquire this noxious quality 
during the ordinary course of cropping. Air and water do not find their 
way through them in sufficient quantity to retain them in a healthy 
condition, and thus they require an occasional fallow with repeated 
ploughings, that the air and the rains may have access to their inner- 
most parts. I do not detail the specific chemical changes which are in- 
duced by this exposure to the air and rain ; it is sufficient that they are 
of a kind to render the soil more propitious to the growth of crops, to 
satisfy us that, upon very stiff lands, one of the benefits of fallowing is to 
be thus accounted for. 

We have seen that one of the important benefits of draining is the 
permeability it imparts to the soil. The surface water is permitted to 
escape downwards, and as it sinks to the drain the air follows it, so that 
the very deepest part of the soil from which the water runs off, is ren- 
dered wholesome by the frequent admission of new supplies of atmos- 
pheric air. 

It thus appears that in a certain sense draining and fallowing may 
take the place of each other — that where there is no drainage, fallowing 
is more necessary and will partially supply its place, and that where a 
good drainage exists, the use of naked fallows even upon stiff clay lands 
becomes less necessary. 

5°. I have already had occasion to speak of the existence of organic 
(animal and vegetable) matter in the soil, in a so-called inert state — a 
state in which it undergoes decay very slowly, and thus only in a small 



THE SOIL IS MANURED BY THE SEA AND THE AIR. 497 

degree discharges those functions for wliich vegetable matter in the soil is 
specially destined. In stiff clays also, the roots of plants, without actu- 
ally attaining this inert state, yet decay with extreme slowness in conse- 
quence of their being so completely sealed up from the access of the air. 
In both cases the frequent and prolonged exposure which a naked fallow 
occasions, induces a more rapid decay of this vegetable matter, or brings 
it into a state in which its elements more readily assume those new 
forms of combination which are capable of ministering to the sustenance 
and growth of plants. 

Among the other compounds which are produced (p. 161) during this 
prolonged exposure and more rapid decay of the organic matter of the 
soil, nitric acid is one which appears to exercise a considerable in- 
fluence upon the future fertility of the land. The favourable action of 
the nitrates in promoting vegetable growth is now well known, and 
the more rapid formation of these compounds, w^hen the land lies na- 
ked to the action of the sun and air, must not be neglected among the 
fertilizing influences of the summer fallow. 

6°. The soil, besides the clay, (quartz) sand and lime of which it 
chiefly consists, contains also fragments of mineral substances of a com- 
pound nature— of felspar, of mica, of hornblende— of those minerals 
which constitute or which occur in the granitic and trap rocks. These 
slowly decompose in the soil — more rapidly also the more freely they 
are exposed to the air — and the substances (potash, soda, lime, magne- 
sia, silica, &c.*) which they contain, are by this decomposition diffused 
more equably and brought within the more easy reach of the roots of 
plants. When these minerals, therefore, exist in the soil, and when 
tlieir constituents are of such a kind as to favour the growth of any given 
plant, the effect of a naked fallow being to produce an accumulation of 
their constituent substances in the soil, it will be so far favourable in pre- 
paring the land for an after-crop of that particular species of plant. 
You are not to be misled, however, by any broad and unguarded state- 
ments of scientiflc men, so as to imagine for a moment that the benefi- 
cial effects of fallowing in any case are to be solely ascribed to the oper- 
ation of this one cause, f 

7°. The rains bring down upon every soil periodical supplies of ail 
those saline substances — common salt, gypsum, salts of lime, of mag- 
nesia, and of potash in minute quantity — which exist in the sea, and of 
nitrate of ammonia, produced or present in the air. If any soil be defi- 
cient in these, then a year's rest from cropping, by allowing them to ac- 
cumulate, may cause the succeeding herbage to exhibit a more luxuriant 
growth. 

8°. The same remark applies to soils into which springs from beneath 
bring up variable quantities of lime and other substances which the wa- 
ters^hold in solution. Such springs are, no doubt, of much benefit in 
some districts, and when the supply they convey is scanty, a year's 
accumulation may impart additional fertility to the fallowed land. 

9°. Besides that beneficial action of the air to which I have already 
adverted (4° and 5°), and which is to be ascribed mainly to the influ- 

• For the constitution of these mineral substances, see pp. 257 to 260. 
t Fallow is the term applied to land left at rest for further disintegration.— l.xGbig's Organic 
Ckemistry applied to Agriculture, p. 14i^. 



498 OF GREEN OR FALLOW CROPS. 

ence of the oxygen it contains — the exposure of the naked soil to the at- 
mosphere for a lengtli of time is said by some to be productive of another 
good effect. The atmosphere contains a small and variable portion of 
ammonia (p. 156). Of this ammonia, a portion is brought down by the 
rains and a portion is probably absorbed by the leaves of plants as they 
spread themselves through the air. But the clay, the oxide of iron, and 
the organic matter of the soil are supposed also to have the power of 
extracting this ammonia from the atmosphere and retaining it in their 
pores. If so, the more the soil is exposed, and for the longer period 
to the air, the more of this substance will it extract and absorb. If 
turned over by frequent ploughing, it will be able to drink it in more 
abundantly, from the greater surface it can present to the passing winds; 
and if, besides, it be kept naked for an entire year, a still larger accumu- 
lation must take place. And as this ammonia is known in many cases 
to be favourable in a high degree to the growth of plants, it is not im- 
reasonable to believe that if thus absorbed in quantity from the air, it should 
be one source at least of the augmented fertility of fallowed land. 

To one or other — or to all of these causes combined — the acknowledged 
benefit of naked fallows is in a great degree to be ascribed. 

O^ green or fallow crops little need be said in addition to what I have 
already laid before you in reference to the rotation of crops. The green 
crop demands a comparatively small supply only of those inorganic sub- 
stances which the corn crops specially require. During its growth, 
therefore, these latter accumulate in the same way, though in a some- 
what less degree than during a naked fallow. But the additional vege- 
table matter and manure which the green crops introduce into the soil, 
and the large supplies of inorganic matter which such of them as are 
deep-rooted bring up from beneath, amply compensate for any diminu- 
tion they may cause in the benefits which are usually derived from the 
naked fallow. 

§ 7. Of ivheat and wheaten flour. 
The grain of wheat in the hands of the miller is readily separated into 
two portions — the husk, which forms the bran, and the greater portion 
of the pollard — and the kernel, which, when ground, forms the wheaten 
flour. The relative weights of these two parts vary very much. Some 
varieties of grain are much smoother, more transparent, and thinner 
skinned than others, and yield in consequence a larger return of the 
finest flour. In good wheat the husk amounts to 14 or 16 percent, of 
the whole weight* — though the quantity separated by the miller is 
sometimes not more than |th (or 11 per cent.) of the weight of the 
wheat. In making the fine white flour of the metropolis and other 
large towns, about |th of the whole is separated in the form of pollard 
and bran. The proportion of the husk that can be sifted out at the mill 

* Boussingault found as much as 38)^ per cent, of husk on a winter wheat grown in the 
botanic garden of Paris. Tliree lots of good English wheat, ground at Mr. Robson's mill in 
Durham, gave per cent, respectively — 

Fine flour 742 751 77-9 

Boxings 90 8-3 61 

Sharps 5 8 6-6 56 

Bran 78 70 69 

Waste 3 2 30 35 

100 100 100 



RELATIVE WEIGHTS OF FLOUR AND BRAN. 499 

depends considerably upon the hardness of the grain. From such as is 
soft it peels off in flakes under the stones, whereas, when the grain and 
husk are flinty, much of the latter is crushed and ground — adding to the 
weight of the flour, but giving it a darker colour, and lowering its quality. 

The country millers generally separate their wheaten flour by sifting 
into four parts only — fine flour, boxings, sharps or pollard, and bran. 
In London and Paris no less than six or seven qualities are manufac- 
tured and sold by the millers.* The value of the wheat to the miller 
depends very much upon the quantity of fine flour it will yield, though 
he cannot always judge accurately of this point by simple inspection. 

The experimental wheats of Mr. Burnet, of Gadgirth,f raised all from 
the same seed differently manured, gave respectively 54^, 63^, 65|, 
66h, 68|, and 76^ lbs. of fme flour from 100 of wheat, so that the hind 
of manure applied to the land appears materially to affect the relative 
])roportions of flour and bran. 

Again, Colonel le Couteur's samples of wheat (p. 489) of different va- 
rieties, grown under the same circumstances, gave from one field 80 1 
and 79| lbs., and from another 72| and 78^ lbs. from 100 of wheat — so 
that wpon the variety of seed sown also, though in a less degree, the quan- 
tity of fine flour is dependent. 

§ 8. Of the composition of wheaten flour. 

1°. Water. — When wheat is kept for ayear it loses a little water, be- 
coming one or two pounds a bushel heavier than before. When put into 
the mill and ground it becomes very hot, and gives off' so much watery 
vapour, that the flour and bran, though together nearly twice as bulky, 
are nearly 3 per cent, lighter than the grain before it was ground. A 
further loss of weight is said to take place when the flour is kept long in 
the sack. If fine flour be slowly heated to a temperature not higher 
than 220 for several hours, it loses a quantity of water, which, in up- 
wards of 20 samples of English flour which I have examined, has varied 
from 15 to 17 per cent, of the wliole weight. It may, therefore, be as- 
sumed, that English flour contains nearly a sixth part of its weight of 
water — or every six pounds of fine flour contain nearly one pound of 
water. 

2". Gluten, albumen, caseine, starch, gum, and sugar. — When the 
flour of wheat is made into dough, and is then washed carefully with 
successive portions of water upon a fine gauze or hair sieve, as long as 
the liquid passes through milky, the flour is separated into two portions — 
the starch, which subsides from the water, and the gluten, which remains 
in the sieve (p. 116). If the water be poured off", after the starch has 
subsided, and be heated nearly to boiling, it becomes troubled, and flakes 
of vegetable albumen (p. 117) are seen to float in it. On setting aside to 

• These sure called respectively in London and Paris — 

London. Paris. Called. 

Fine flour. White flours, 1st quality, de ble. 

Seconds. do. 2d do, de le gruau. 

Fine middlings. do. 3d do. de 2e gruau. 

Coarse middlings. Brown meals, 4th do. de 3e gruau. 

Pollard. do. 5th do. de4e gruau. 

Twentypenny. ' Bran, fine and coarse. 

Bran Waste, &c., Remoulage and Recoupe. 

t Page 362, and Appendix, pp. 54 and 70. 



600 STARCH, SUGAR, UUM, AND OIL, IN WHEAT. 

cool, the flaky powder falls to the bottom, and may be collected, dried, 
and weighed. If the water, after filtration, be evaporated to dryness on 
the water bath, a residue will be obtained, Avhich consists chiefly of solu- 
ble sugar, gum, and saline matter, with a little fatty matter, and sparingly 
soluble caseine* (p. 117). 

3°. Glutine and oil. — If, further, the crude gluten be boiled in alco- 
hol, a solution is obtained which, on cooling, deposits a white flocky sub- 
stance, having much resemblance to caseine. When the clear solution is 
concentrated by evaporation, water separates from it an adhesive mass, 
which consists of a substance to which the name of glutine is given, 
mixed with a little oil. By digesting the mixed mass in ether the oil is 
dissolved out from the glutine, and may be obtained in a pure state by 
evaporating the ethereal solution. This oil possesses the general pro- 
perties of the fatty oils, or of butter. As it is partly washed out, how- 
ever, along with the starch, the whole of the fatty matter of the flour is 
best obtained by boiling it in a considerable quantity of ether. 

4°. Vegetable fihrine. — The crude gluten, after boiling in alcohol, has 
much resemblance to the fibre of lean beef, and has therefore been named 
vegetable fibrine. When burned, it leaves behind an ash, containing, 
among other substances, the phosphates of lime and magnesia, which 
are to be considered also as among the usual constituents of wheaten 
flour, f 

Thus, fine wheaten flour, in addition to the water it contains, and to 
the small quantity of bran which is ground up along with it, consists of 
vegetable fibrine, albumen, caseine, glutine, starch, sugar, gum, oil or 
fat, besides the saline substances, chiefly phosphates, which remain in 
the form of ash, when the flour is burned. All these substances vary in 
quantity in different samples of flour, — their relative proportions appear- 
ing to depend upon a variety of circumstances as yeX. little understood. 
In the various analyses of flour that have hitherto been published, little 
attention has been paid to the per-centage of oil, of glutine, or of caseine, 
which the specimens examined have severally contained. In general, 
the weight of the crude gluten only has been estimated, without extract- 
ing from it either the oil or the glutine. 

The following table exhibits the approximate composition of some 
varieties of French and Odessa flour as determined many years ago by 
VauquelinJ : — 

* This caseine begins to form a pellicle on the surface, when the liquid is concentrafed by 
evaporation, and though it is generally present only in a small proportion (Jtf to 1 per cent.), 
yet the comparative quantities present in two samples of flour may be judged of by the 
abundance in which the pelUcle is formed. 

t The saline and other inorganic matter of grain resides chiefly in the husk, as may be 
seen by the relative quantities of ash left by the flour, bran, &c., of several seimples of Eng- 
lish and Foreign wheat as determined in my laboratory — 

„,„ „ „„„„,„ ASH LEFT PER CENT. BY DRY. 

WHERE GROWN. Fine Flour. Boxings. Bharps. Bran. 

1°. Sunderland Bridge, near ^ j.g^ a.q g.g g.g 

Durham \ 

2°. Kimblesworth, do 115 3-8 4-9 6-7 

30. Houghall, do 0-96 30 5-6 71 

40. Plawsworth, do 093 2-7 5-5 7-6 

5°. Stettin 11 4 5 6-2 69 

6°. Odessa 11 49 ' 66 80 

t Dumas' Traite de Chimie, vi. p. 388. 



ON THE COMPOSITION OF WHEATEN FLOUR. 



501 



COJIPOSITION OF THE FLOUK OF 

French Wheat. Odessa Wheat. 



1st 2d 

quality, quality. 

Water 10 120 

Gluten 110 7-3 

Starch 715 720 

Sugar 4-7 54 

Gum 3 3 3-3 

Bran — — 

100-5 100 



Paris 
Bakers' 

Flour. 
10 
101 
72-8 

4-2 

2-8 



100 



Flinty 
Wheat. 

120 
14-6 
56-5 
8-5 
4-9 
2-3 

98-8 



Soft Wheat. 

1st 2d 

quality, quality. 



100 

120 

620 

7-4 

5-8- 

1-2 



8 

120 

70-8 

4-9 

4-6 



1-4 l()0-3 



§ 9. Of the influence of soil and climate on the com/position of 
wheaten flour. 

1°. The nature of the soil has a sensible influence upon the composi- 
tion of the grain that is reaped from it. The proportion of gluten, for 
example, is said to be generally greater in grain which is reaped from 
calcareous soils, or from such as abound in organic matter. In the north 
of Ireland, this fact has been observed in regard to the wheat grown in 
the limestone districts ; and the millers of the midland counties of Eng- 
land (on the new red sandstone) are accustomed to mix, with their native 
corn, that of the chalk districts to the east and south, for the purpose of 
giving additional strength to their flour. 

Climate. — The wheat of warm climates also is supposed usually to 
contain more gluten. Thus flour, prepared from some Eastern wheats, 
compared with that from others of French growth, was found to contain 
water and dry gluten in the following proportions: 

French, Saissette 
Rochelle 
Brie 
Tuzelle 
Odessa 
Taganrog* . 

The quantity of gluten contained 
stated much too high. Thus, Sir Humphrey Davyf says that he ob- 
tained from the flour of — 

Gluten, Gluten, 

per cent. per cent. 

English winter wheat 19 Barbary wheat 23 

English spring wheat 24 Sicilian wheat 21 

— and others have given numbers nearly as high. But the gluten is 
very difficult to dry, and I believe that the large per-centage of this sub- 
stance assigned by previous experimenters has arisen from the water not 
being sufficiently expelled from it by prolonged heating to 220° F. I 
select the following from a greater number of determinations, carefully 
made in my laboratory '.— 



Water, 


Gluten, 


per cent. 


per cent. 


15-1 


12-7 


12-9 


11-2 


13-5 


10-7 


13-0 


8-3 


13-0 


15.0 


12-6 


22-7 



in English flour has generally been 



* Taganrog, at the head of the sea of Asoph, exports the produce of the banks of the 
Don. 

* Agricultural Chemistry^ Lecture III. 



502 INFLUENCE OF CLIMATE, VARIETY OF SEED, 

Weight Water 

per in Gluten. 

KiNP OP WHEAT, bushel. Flour. wnBRE grown. 

lbs. per ct. per ct. 

Red English.... 62* 17-5 81 At Sunderland Bridge, near Durham. 

«• " .... 62| 16-4 9-5 At Kimblesworth, near Durham. 

«« «« .... 63 150 8-5 At Houghali, near Durham. 

«' «* ..., 62| 16-8 9-9 Near North Deighton, Yorkshire. 

White" .... 63 155 75 At Plawsworth, near Durham. 

" Scotch., 61^ 16-3 9-4 At Gadgirth, near Ayr (Appendix, p. 59.) 

Red Stettin 63 14 6 86 

« Odessa.... 61 159 11-5 

In all these cases the quantity of gluten falls far short of that assigned to 
English flour by Davy ; yet we may safely, I think, conclude from them 
that English flour seldom contains more than 10 per cent, of dry gluten. 
The flour from North Deighton, which gave 9*9 per cent, was grown 
upon a thin limestone soil, and may perhaps owe its larger per-centage 
to this circumstance. 

But these numbers do not indicate the exact quantity of nitrogen-hold- 
ing food which these flours contained. For in the gluten there is al- 
ways present avariablequantityof fatty matter which contains no nitrogen, 
and which, if extracted, would lessen considerably the weight of the glu- 
ten in some of the flours. On the other hand, however, the water em- 
ployed in washing out the .starch holds in solution some albumen and 
casein, which, having the same composition, might be added to the glu- 
ten, and would sensibly increase its weight. Thus in a sample of flour* 
grown in Ayrshire I found- 
Gluten .... 9*3 per cent. 
Albumen .... 0*45 per cent. 
Casein .... 0*40 per cent. 

Making in all . . . 10-15 of substances which contain 
nitrogen in nearly equal proportions. 

We probably, therefore, do not greatly err in general in estimating 
the nutritive value of wheaten flour — in so far as it depends upon these 
nitrogenous compounds — ^by the per centage of dry gluten which a care- 
ful washing enables us to separate from it. Further researches, how- 
ever, which are now in progress, will throw much additional light upon 
this subject. 

§ 10. Influence of variety of seed, of mode of culture^ of time of cuttings 

and of special manures, on the composition ofwheatt 

1°. Variety of seed and mode of culture. — The influence of these two 

circumstances upon the relative proportions of bran and gluten are .shown 

by the following results of the examination by Boussingaultf of several 

varieties of wheat grown in the Botanic Garden at Paris — 

Husk or Bran Flour Water Gluten, &c. 

in the Grain, in the Grain, in the Flour, in the Flour, 

per cent. per cent- per cent. per cent. 

Capewheat 19 81 7-0 206 

Russian wheat 18 82 64 24 8 

Dantzic wheat.. 24 76 7-3 25-8 

Red Foix wheat 18-5 815 9-3 261 

Barrel wheat 22 78 8-8 277 

Winter wheat 38 62 141 33 

• No. 2. Appendix, p. 171. 

t Annates de Chim. et de Phys. Ixv., p. 311. 



TIME OF CUTTING, AND SPECIAL MANURES. ' 503 

In all the samples the bran and gluten are both very high, but they 
vary much in the several varieties. 

The gluten includes the albumen and casein and other substances con- 
taining nitrogen, but even though grown in the rich soil of a botanic gar- 
den, I fear the sum of these has been estimated much too high.* The 
same variety of wheat grown in the open fields in Alsace gave 17*3 of 
gluten, and in the Botanic Garden of Paris, 26*7 of gluten. 

2° . The time of cutting affects the weight of produce, as well as the 
relative proportions of flour, bran, and gluten. Thus from 3 equal patch- 
es of the same field of wheat upon thin limestone soil at North Deighton, 
in Yorkshire, cut respectively 20 days before the crop was fully ripe, 10 
days before ripeness, and when fully ripe, the produce was in gxainr-' 
20 days before. 10 days before. Fully ripe. 

166 lbs. 220 lbs. 209 lbs. 

and the per-centage of flour, sharps, and bran, yielded by each, and of 
water and gluten in the flour, was as follows : — 

IN THE GRAIN PER CENT. IN THE FLOUR PER CENT. 
WHEN CUT. ,. ' -^ , V 

Flour. Sharps. Bran. Water. Gluten. 

20 days before it was ripe 747 72 17-5 157 9-3 

10 days before. 79-1 5-5 13-2 15-5 99 

Fully ripe 72-2 110 160 159 96 

When cut a fortnight before it is ripe, therefore, the entire produce of 
grain is greater, the yield of flour is larger, and of bran considerably less, 
while the proportion of gluten contained in the flour appears also to be 
in favour of that which was reaped before the com was fully ripe.j 

3°. Special manures. — It is said that the employment of manures 
which are rich in nitrogen not only causes a larger crop, but also produ- 
ces a grain which is much richer in gluten. The experiments which 
have hitherto been chiefly relied upon in proof of this result are those of 
Hermbstadt. On ten patches, each 100 square feet, of the same soil (a 
sandy loam) manured with equal weights of different manures in the dry 
state, he sowed equal quantities (i lb.) of the same wheat — collected, 
weighed, and analysed the produce. His results are represented in the 
following table : — 

«l .^ |§ |§ M o§ |§ l§ ^3| p 

Oxi Z 09 02-73 U-c ma 33t3 Pk-o O-v > a Pa 

Return Hfold. 14 fold, la fold. ISfold. ISfold. lOfold. 9fold. 7fold. Sfold. 3fold. 

Water 4-3 4-2 4-2 4-3 4-2 4-3 4-3 4'2 4-2 4-2 

Gluten 34-2 33-9 32'9 32-9 35-1 13-7 12-2 12-0 9-6 9-2 

Albumen 1-0 1-3 1-3 1-3 1-4 M 0-9 1-0 0-8 0*7 

Starch 41-3 41-4 42-8 42-4 39-9 61-6 63-2 62-3 65-9 66-6 

Sugar 1-9 1-6 1'5 1-5 1-4 1*6 1-9 1-9 1-9 1-9 

Gum 1-8 1-6 1-5 1-5 1-6 1-6 1-9 1*9 1-6 1-8 

FattyOil 0-9 M 10 0-9 1-0 10 0-9 I'O 1-0 1-0 

SolublePhosphates,&c. 0-5 0-6 07 07 0-9 0-6 0-5 0-5 0-5 0-3 

Husk and bran 13-9 14*0 13-8 14-2 14-2 14-0 14-0 14-9 14'0 14-0 

99'8 99-7 99-7 997 997 99-6 99-8 997 99-8 99-7 
The large per-centage of gluten obtained by the use of the first five 

• In these flours the gluten was not determined by washing out the starch, but by a more 
refined method of ultimate analysis, as it is called, by which the per-centage of nitrogtin ia 
determined, and the proportion of gluten, «&c., calculated from this. When the per-centage 
of nitrogen is small, as in wheaten flour, (his method is open to many sources of error. 

* See a paper by Mr. John Hannam, Quarterly Journal of Agriculture, Iviii., p. 173. 



604 EFFECTS OF GERMINATION AND BAKING 

manures is very striking, if the determinations are really to be depended 
upon. They are certainly interesting in a theoretical point of view, and 
are deserving of careful repetition. In reference to their bearing upon 
practical farming, however, it must not be forgotten, that the results of 
small experiments are never fully borne out when they are repeated on 
the large scale — that the relative value of different animal manures is 
materially affected by the kind of food on which the animal has lived — 
that independent of manures, there are circumstances not yet made out 
which materially affect the produce of single patches* — and that it will 
rarely be in the power of the practical farmer to apply at pleasure to his 
fields the relative proportions of the several manures used by Hermb- 
stadt. Thus, if instead of 20 tons of farm-yard m.anure he wished to 
try blood or urine alone, he must apply 24 tons of the former, and 70 
tons of the latter — quantities which it might be both difficult to procure 
and inconvenient to apply. 

The most practically useful results yet published in regard to the ac- 
tion of the different manures upon the weight of the crop, the proportion 
of flour yielded by it, and of gluten in the flour, are those of Mr. Burnet, 
to which I have already had occasion to draw your attention. f These 
results were as follow : — 

,„^,„ «„ «.«TrT,r. Produce Fine Flour Gluten 

KIND OP MANURE. per acre. from the grain, in the flour. 

Nothing 311 bshls. 76§ lbs. 9-4 per cent. 

Sulphated urine and wood ashes. 40 " 66^ " 10-5 " 

Do. and sulphate of soda. 49 " 63^" 9-7 " 

Do. and common salt. . 49 " 65f " 9-6 " 

Do. and nitrate of soda. . 48* " 54f " 10-0 " 

We perceive here a slight increase in the per-centage of gluten when 
the manures were applied, but nothing which at all resembles the great 
differences given by Hermbsatdt, or which renders it probable that by 
skilful management, as some have supposed, we may hereafter be 
able to raise in our fields whole crops of corn which shall yield a flour 
containing 20 or 30 per cent, of gluten. 

§ 11. Of the effects of germination, and of baking, upon the flour of wheat. 

The effects of germination and of baking upon the flour of wheat are 
very analogous to each other. In both cases, a portion of the starch is 
changed into gum and sugar. 

1°. Gerrnination. — I have already described to you (p. 118), the very 
beautiful change which takes place during the sprouting of the seeds of 
plants — how a portion of their gluten is changed into diastase, and how, 
by the agency of this diastase, the starch of the seed is changed into gum 
and sugar. In an experiment made by De Saussure, 100 parts of the 
farina of wheat had by germination lost 6 parts of starch, and in their 
stead had acquired 3^ of gum and 2i of sugar. The eflfect of this 
change — which proceeds as the plant continues to grow — is to make the 
starch soluble, and thus capable of entering into the circulation of the 
young plant. 

2°. Baking. — It is the larger proportion of gluten usually contained 
in the flour of wheat that renders it so much better fitted for the bakini*- of 

• See Appendix, pp. 59 and 79. T See p. 362 and Appendix pp. 49 and 71. 



UPON THE FLOUR OF WHEAT. 505 

bread than the flour of any other grain. If the gluten be washed out of 
the flour, and put alone into the oven, it will swell up, become full of 
pores, and assume a large size. The comparative baking qualities 
of different samples of flour may be judged of by the height to which, in 
similar vessels, the gluten of equal weights of flour is thus observed to rise. 

We have already seen that by heating in an oven, dry starch is gra- 
dually changed into gum {British gum, p. 113), and into a species of 
sugar — becoming completely soluble in water. Such a change is pro- 
duced upon a portion of the starch of wheaten flour when it is baked in 
the oven. Thus in 100 parts of the flour, and of the bread of the same 
wheat, Vogel found respectively — 

Starch. Sugar. Gum. 

Flour ... 68 5 — 

Bread . . . 53i 3| 18 

So that a very considerable portion of gum had been produced at the ex- 
pense of the starch. 

The yeast which is added to the dough in baking, acts in the same 
way as when it is added to the sweet wort of the brewer. It induces a 
fermentation by which the sugar of the flour is changed into carbonic 
acid and alcohol. The carbonic acid is liberated in the form of minute 
bubbles of gas throughout the whole substance of the dough and causes 
it to rise, the alcohol is distilled off" in the oven. If too much water 
have been added to the dough — or if it have not been sufficiently knead- 
ed — or if the flour be too finely ground — or if the paste be not sufficiently 
tenacious in its nature, these minute bubbles will run into each other, 
will fonn large air holes in the heart of the bread, and will give it that 
open irregularly porous appearance so much disliked by the skilful 
baker. Good bread should be full of small pores and uniformly light. 
Such bread is produced by a strong flour ; that is, one which will rise well, 
will retain its bulk, and will bear the largest quantity of water. 

The quantity of water which wheaten flour retains when baked into 
bread depends in some degree upon the quality of the flour. In the 
Acts of Parliament relating to the assize of bread, it is assumed that a 
sack of flour (280 lbs.) will produce 80 quartern loaves, or 320 lbs. of 
bread. According to this calculation the flour should take up and retain 
when baked one-seventh of its weight of water. But the quantity of water 
retained by the flour now in use is very much greater, and the profit to 
the baker, therefore, very much more than this calculation supposes. 

This is shown by the quantity of water which is lost by wheaten 
bread, whether of first or second quality, when it is dried by prolonging 
heating, at a temperature not exceeding 220° F. The home-made 
bread (white and brown) baked in my own house, and in two other 
private houses in Durham, lost of water by drying in this way — 







How long baked. 


Water per cent 


1°. 


White 


24 hours. 


43-3 




Brown* 


24 do. 


44-0 


2°. 


Brown 


42 do. 


44-1 




White 


36 do. 


42-9 


3°. 


White 


9 do. 


44-1 



* The brown bread is made from the whole grain of the wheat as it comes from the 
millstones— nothing being separated by sifting. 



$06 WATER TAKEN UP BY FLOUR IN BAKING. 

So that wheaten bread one day old contains about 44, and two days oldJ 
about 43 per cent, of water. Something, however, will depend upon' 
the size of the loaves. 

This proportion is almost exactly the same as that contained in the 
white bread of Paris. According to Dumas, the water in the commoi 
white bread of Paris amounts to — 

Hours baked. Water per cent 

2 ....... 45-7 



4i 
10 
24 



45-3 

43-0 
43-5 



We may assume, therefore, 44 per cent, as very nearly the average 
quantity of water contained in good white bread both in England and in 

France. Bread baked for public establishments contains more water, 

not being generally so well fired, or being baked in the form of many 
loaves stuck together, instead of in separate tins, as is done with home- 
made bread. Such is the case with the soldiers' bread of our own 
country, and the barrack bread of Paris (pain de munition) which con- 
tains about 51 per cent, of water. 

We have already seen (p. 499) that English wheaten flour contains, on 
an average, about 16 per cent, of water. If, therefore, the bread baked 
from it, as it comes from the mill, contain 44 per cent., every hundred 
pounds consist of — 

Dry flour 56 ) 

Water in the flour (naturally) . lOi^ { ^^^ 

Water added by the baker . . . " . 33^ 

Or, the flour, in baking, takes up half its weight of water. A hundred 
pounds of flour, therefore, as it comes from the mill, will give very 
nearly 150 pounds of bread. Thus — 

-r» a ^^^^ contains Bread contains 

Dry flour .... 84 84 

Natural water, ... 16 16 

Water added . . 50 

100 

Weight of bread 150 
A sack of flour, therefore, or 280 lbs., ought to give about 420 lbs. of 
well baked bread. Something must be deducted from this for the loss 
by fermentation, and for the dryness of the crusts. Allowing 5 per cent, 
for these, a sack of flour should give 400 lbs. of bread of the best quality * 
or 100 quartern loaves. The cost of fine white bread, therefore, com- 
pared with that of corn and flour, ought to be very nearly as follows : 

««.«.l,^°^°'"^^°"^ Cost of Bread, Market price of 

per sack, per stone. per quartern loaf. Grain per art 

35s. Is. 9d. 4|d. 47s 

40s. 2s. Od. 4|d. 52s! 

• Unmixed with potatoes, which are employed by many bakers in considerable quantity. 
Mixed with the yeast they are said to make the bread lighter. 

T t'^4'\'^°^"'"".,^*^ ^^^"^ calculated for me, from the price of the flour, by my friend Mr 
John Robson, miUer,m Durham. The practical rule is, that 6 bushels of com should give 
one sack of flour, and that the miller should have the oflfel for his trouble. 



RELATIVE COST OF CORN, FLOUR, AND BREAD. 507 



Cost of Flour, 
per sack. per stone. 
45s. 2s. 3d. 


Cost of Bread, 

per quartern loaf. 

5fd. 


Market price of 
Grain per qr. 
60s. 


50s. 


2s. 6d. 


6d. 


67s. 


55s. 


2s. 9d. 


6id. . 


72s. 


60s. 


3s. Od. 


7id. 


80s. 



The economy of baking at home, therefore, at the usual prices of 
bread, seems to be very considerable. 

§ 12. Of the supposed relation between the per-centage of gluten in 
Jlour, and the iveight of bread obtained from it. 
It has been assumed by recent chemical writers that the quantity of 
water absorbed by flour, and consequently the weight of bread obtained 
from it, depends, in whole or in great part, upon the proportion of gluten 
which the flour contains. The following facts, however, do not accord 
with this supposition. 

1°. Household bread, made respectively from the flour of a French 
wheat and of a wheat from Taganrog, retained nearly the same per- 
centage of water, though the one sample contained upwards of twice as 
much gluten as the other. Thus — 

Gluten per cent. Water per cent, 

in the Flour, in the Bread. 

Flour of Brie . . . 10-7 47-4 

Flour of Taganrog . . 22-7 47-0 

This one fact might be supposed to settle the question, but I shall 
mention others. 

2°. The flour from Odessa wheat contains about \\h more gluten than 
French flour in general, and yet it absorbs very little more water (Du- 
mas). This Dumas accounts for by the fact that the starch of the 
Odessa wheat forms hard transparent horny particles, which take less 
water to moisten them than the impalpable powder yielded by the softer 
French wheats — so that the gluten does not appear to produce its full 
effect. I do not know how far this explanation is consistent with the 
fact that the hard flinty wheats give the best biscuit flour — what the 
baker calls the strongest, which rises best, and absorbs the most water.* 

3°. Rice is said to contain very little gluten — not estimated by any to 
amount to more than 6 or 7 per cent. — and yet it is stated as the result of 
numerous trials, that an admixture of a seventh part of rice flour causes 
wheaten flour to absorb more water, f 

4°. If the hard wheats be ground too fine they lose a part of their ap- 
parent strength, the flour becomes dead, as it is sometimes called, and 
refuses to rise as it would do if sent to the baker in a more gritty and less 
impalpable state. 

5°. Lastly, the admixture of very minute quantities of foreign matter, 
by way of adulteration, is said to have a remarkable influence upon the 
quantity of water which the flour will absorb. In some parts of Belgium 
it appears to have been the practice to adulterate the bread with a small 
quantity of sulphate of copper.J This salt is dissolved in water, and 

* That such is the case also in foreign countries, see a letter from the British Consul at 
Lisbon, in Davy's Agricultural Chemistry, Lecture IIL 
t Dumas' Traite de Chimie, vi., p. 396. 
t Blue vitriol— a violent poison. 
22 



508 COMPOSITION OF BARLEY. 

the solution added to the water with which the dough is to be made, in 
the proportion of about one grain to two pounds of flour. It gives the 
bread a fairer colour, and thus permits the use of inferior flour, and it causes 
the bread to retain about six per cent, more water without appearing moist- 
er. Even in the small proportion of one grain of the sulphate to 6, or 
7 lbs. of flour, it produces a very sensible effect (Kuhlman). 

Other adulterations also exercise a similar influence. Alum improves 
the colour of the bread, raises it well, and causes it to keep water, but it 
requires to be added in larger quantity than the more poisonous sulphate 
of copper. Common salt likewise makes the paste stronger, and 
causes it to retain more water, so that the addition of salt is a real gain 
to the baker. 

From all these facts, therefore, we may infer that, independent of the 
relative proportions of gluten, very shght differences in composition — 
8uch as have not yet been sought for or appreciated — may materially 
affect the relative weights of bread obtained by the baker from different 
samples of wheaten flour. 

§ 13. Of the composition of barley^ and the influence of different manures 
upon the relative proportions of its several constituents. 

The grain of barley consists of nearly the same substances as that of 
wheat, but in proportions somewhat different. These proportions, how- 
ever, are affected both by the kind of manure with which the land is 
dressed, and by the nature of the soil on which the seed is sown. 

1°. Manure. — The effect of manure appears from the following table, 
containing the results of Hermbstadt, obtained in the same way as those 
with wheat already described (p. 503) :— 

KIND OP S 'SSseS <3S -Soiajg^ 

MANURE. ^ 3 2 a% & ^3 =|^2oa5>-« . 

OxBlood 10'4 13-6 5-7 0-4 59-9 4-6 4-4 4 04 16 

Night-soil 102 13-6 5-8 0-5 59-6 4-5 4-3 0-5 0-6 13 

Sheep's dnng... 10-3 13-5 5-7 0-4 59-9 4-6 4-4 0-4 0*3 16 

Goat'sdung 10-4 135 5-7 0-4 599 4-6 4-5 0-4 0-3 15 

Human urine... 10-3 13-6 5-9 Oo 59-6 4'4 44 0-4 0-7 13| 

Horsedung 10-4 135 57 0-4 59-7 4-6 45 0-4 0-4 13 

Pigeon's dung.. 10-4 13'5 5-6 0-4 59-8 46 45 0-4 0-4 10 

Cow'sdung 10-8 13-6 33 0-2 619 4-8 4-6 0-3 0-3 11 

Veget. manure.. 10-8 13-6 2-9 0-2 62'2 4-9 4-8 0-2 0-1 7 

No manure 10 8 13-6 2-9 0-1 62-5 50 4-7 Q-l 0-1 4 

In SO far as reliance is to be placed upon the numbers in the above 
table, as indicative of the general effect of the several manures men- 
tioned, it would appear that the relative proportions of gluten, albumen, 
and starch do not vary very much until we come to cow-dung, when the 
former two substances sensibly diminish. Further experiments, how- 
ever, are required upon this subject (see page 514). 

2°. Soil. — The effect of soil upon the barley crop is known to all 
practical farmers — so that the terms barley-land and wheat-land are the 
usual designations for light and heavy soils adapted especially to the 
growth of these several crops. On clay lands the produce of barley is 
greater, but it is of a coarser quality, and does not malt so well — on 
loams it is plump and full of meal — and on light chalk soils the crop is 
light, but the grain is thin in the skin, of a rich colour, and well adapted 



EFFECT OF MALTING UPON BARLEY. 509 

for malting.* The barley of the light lands in Norfolk is celebrated in the 
Nortli of England for its malting properties — and the brewers refuse the 
barley of the county of Durham, even at a lower price, when Norfolk 
barley is in the market. When unfit for malting, barley affords a fat- 
tening food for pigs and for some other kinds of stock. 

§ 14. Effect of malting upon barley. 

During the germination good barley increases in bulk one-half. In 
order tliat it may do so, it must be uniformly ripe — a quality of great 
value to the maltster. This maximum bulk is generally acquired in 24 
hours after it has been moistened and laid in heaps. In drying, how- 
ever, tlie barley again diminishes in bulk, so that the dried malt rarely 
exceeds by more than ^-^th or f^th the bulk of the grain as it came from 
the market. The well-dried malt, however, is lighter by -^th tnan the 
barley from which it is made — 100 lbs. of barley yielding about 80 lbs. 
of malt. This is not all loss of substance, since by a similar drying the 
barley itself before malting would lose about 12 per cent of water. The 
loss of substance, therefore, is only about 8 per cent. This diminution 
of solid matter arises in part from the loss of the little roots which form 
the malt-dust {cummins), of which I have already spoken (p. 436) as 
being a valuable manure, and of which 4 or 5 bushels are obtained from 
100 bushels of barley. 

The colour of the malt varies with the temperature at which it is dried. 
If the heat does not exceed 100° F. a very pale malt is obtained, which 
gives a very white beer. A heat not rising above 180° gives an amber 
coloured malt — while for brown malt the temperature may rise as high 
as 260° F. By mixing these varieties beer of any colour may be made. 
But in the porter breweries it is usual to prepare a quantity of malt of a 
brownish black colour {buriied malt), by adding a portion of which any 
required shade of colour is imparted to the liquor. 

During germination a variable quantity of the gluten is converted into 
diastase (p. 119), and about two-fifths (40 per cent.) of its starch mto 
sugar or gum (dextrine). The quantity of diastase produced depends 
upon the extent to which the germination has proceeded. It is greatest 
at the moment when the gemmide is about to burst from the seed, and to 
form the young shoot. 

I have already explained the beautiful purpose served by this diastase 
in converting the insoluble starch of the grain into soluble sugar and 
gum. When the beer is to be made wholly from malt, it is unnecessary 
to continue the germination till the largest quantity of diastase is pro- 
duced. It is sufficient if the gemmule, on holding up a grain of the 
barley, be seen within the skin to have attained one-half or two-thirds of 
the length of the seed. The diastase then produced is more than enough 
to convert the whole of the starch of the grain into sugar (p. 120). But 
if raw grain, as in some of our distilleries, is to be added to the malt, 
then the malting should be prolonged till the bud is about to burst through 
the husk, so that the largest possible supply of diastase may be contain- 
ed in it. In this way also malt is prepared when it is to be employed 

* " The barlev on the compact clays (in Hants)isof a coarser quality, but produce greater— 
on the light chalk soils it is well calculated for malting— the skin is thin, and colour rich but 
light— in fullness of meal and plumpness of appparance it never equals the barleys grown in 
Staffordshire, and upon loamy lands."— Mr. Gawler in British Husbandry, iii. p. 12. 



510 COMPOSITION OF OATS AND RYE. 

in the manufacture of syrup {glucose) from potatoe flour — a branch of in- 
dustry which has become of some '.mportance in certain parts of France. 

§15 . Composition of oats, and effect of manures in modifying that composition. 
The relative proportions of husk and meal in the several varieties of 
the oat differ in a greater degree, probably, than in any other grain. 
Thus, the potatoe-oat is known to be richer in meal, the Partary-oat in 
husk. The round grain of the former is chiefly grown in Scotland, for 
grinding into meal, the latter in England, for feeding horses. 

But even the round potatoe-oat varies much in the produce of meal 
which it gives. Many samples yield only half their weight of oatmeal, 
others 9 stones out of 16, while some give as much as 12 stones from the 
same quantity, or three-fourths of their weight. In one variety of oat 
Vogel found 66 per cent, of meal and 34 of husk, which is equal to 10^ 
stones of meal from 16 of grain. He also extracted from the meal 2 per 
cent, of oil, and 59 of starch, and observed it to lose by drying upwards 
of 20 per cent, of water. 

Soil, season, climate, variety of seed sown, and the kind and quantity 
of manure applied — all affect the amount of produce and the chemical 
composition of the oats that are reaped. According to Hermbstadt, the 
eSect of different manures in modifying the composition of the produce 
of the same seed are represented by the numbers in the following table : 

KIND OP « 'SSiegtfri -e^S Sr-,-6 

MCAWTJRE. ^ 35S«S^3~ -15^ O «u^ 

OxBlood 120 19-3 50 04 53-1 38 5-5 03 0-4 12V 

Night-soil 12-1 19-2 4-6 0-4 53-3 3-8 54 03 0-5 Uh 

Sheep's dung... 12-6 13-3 4-0 05 540 5'2 5-5 03 0-4 14 

Goat'sdung 12-9 17-0 4-3 0-4 53-2 54 57 03 0-4 15 

Human urine... 13-0 17-0 44 05 53-1 50 57 04 0-6 13 

Horse dung 13-1 160 40 0-5 54-5 5-2 56 0-3 0-5 14 

Pigeon's dung .. 12-3 18-3 3-2 0-3 53-2 50 68 03 0-3 12 

Cowdung 11-6 15-0 31 0-3 55*0 68 73 03 0-3 16 

Veget manure.. 10-8 130 20 0-2 59-9 64 70 0-2 0-2 13 

Tnmanured 10 8 120 1-9 02 600 6-4 70 0-3 0-1 5 

The differences in tliis table are very striking [see p. 515]. 

§ 16. Composition of rye, and effect of different manures upon its composition. 
The grain of rye approaches nearest to that of wheat in the quantity 
of gluten it contains, and in the consequent fitness of its flour for baking 
into bread. It sometimes also contains much sugar — recent rye-bread 
having almost invariably a sweet taste — but the proportion of sugar ap- 
pears to be by no means constant. Thus Einhof and Greif exhibit the 
composition of a sample of rye-flour, examined by each of them, re- 
spectively as follows : — 

Einhof, per cent. Grief, per cent. 

12-8 

3-0 

58-8 

10-4 

7-2 

7-8 

100 100 



Husk . 


. 6-4 


Gluten (not dried) 


9-5 


Albumen . 


3-3 


Starch . . . 


6M 


Sugar . . 


3-3 


Gum . , 


IM 


Loss . . 


5-3 



COMPOSITION OP RICE. 511 

Perhaps no great degree of faith is to be placed in these analyses. If 
they are to be depended upon, they show that very remarkable differ- 
ences indeed may exist in the relative proportions of some of the consti- 
tuents of rye flour. The flour of rye is said to be more absorbent of 
moisture from the air than that of any other grain.* 

Rye delights in a sandy soil, and is cultivated in general in such as 
are poor in vegetable matter, and to which manure is not very abun- 
dantly added. The experiments of Hermbstadt, whose results are ex- 
hibited in the following table, do not show any very striking difference 
to have been produced upon the composition of the grain by the use of 
the different animal manures ; — 

U .C fit iT >— '.MFo 

KIND OV S -M B ri ri P Se -SmS 3rH'0 

MANURE. ^ 3 =|§5 S'ad iJ^d «J,g 

> K O <B :n WOO rcia.n.'S PS^ao 

OxBlood 10 1 10-4 120 3-6 52-2 3-6 6-2 1-0 0-8 14 

Nightsoil 100 10-7 11-9 3-2 52-4 3-5 6-3 0-9 0-9 13^ 

Sheep's dung... 100 108 11-9 3-4 52-3 3-6 6-1 M 0-6 13 

Goat'sdung. ...100 10-8 11-9 34 522 35 6-0 1-0 0-9 12^ 

Human urine... 10-1 108 120 3-5 502 3-3 4-6 1-1 4-2 13 

Horsedung 100 10-7 11-9 2-8 512 40 4-6 1-0 3-6 11 

Pigeon's dung.. 10-1 10-5 11-6 3-7 52-2 3'7 4-7 0-9 2-3 9 

Cow dung 10-0 10-4 108 2-0 543 3-9 5-7 0-9 1-8 9 

Veget. manure.. 10 10-7 8-8 2-6 55-1 4-8 5-2 0-9 1-7 6 

Unmanured 10 lO-l 86 26 56-3 4'7 5-4 0-9 1-3 4 

The above table exhibits a. larger increase in the return or produce 
from some of the animal manures than from others, but we do not see 
any of those remarkable differences in the composition of the flour, which 
are observable in the results obtained by the application of different 
manures to the wheat crop. 

The substance extracted from rye, and called gluten by Hermbstadt, is 
different from the gluten of wheat, and is more like the glutine extracted 
from the latter grain. When dough made of rye flour is washed in 
water, it nearly all diffuses itself through the liquid, leaving little more 
than the husk or bran behind. The starch deposits itself from the milky 
liquid, or may be separated by the filter. When the liquid is evaporated 
to dryness, and the dry mass boiled in alcohol, the so-called gluten is 
dissolved out, and may be separated from the alcohol by distillation. It 
must then be washed with water to free it from sugar. Like the gluten 
of wheat, it is now insoluble in water, and is less cohesive than gluten. 
Both of these forms of gluten are supposed to have the same composi- 
tion as vegetable fibrin and albumen, and as the curd of milk. 

§ 17. Composition of rice, maize {Indian corn)^ and buck-wheat. 

1°. Rice is usually supposed to differ from other kinds of grain by the 
larger proportion of starch which it contains. 

The large quantities of rice consumed by the native inhabitants of 
India, and of other warm countries, has often appeared surprizing to 
foreigners. Chemists have explained this alleged fact by supposing the 
small per-centage of gluten contained in rice, as shown by the following 
analyses, to be insufficient for the sustenance of the body — when no 
other food is used — unless this grain be eaten in exceedingly large quan- 

* A sample of rye meal, dried in my laboratory, lost only 14X per cent, of water, and of 
rye bread leavened 44, and yeasted 46 per cent. This rye meal may possibly hare been 
mixed. 



il2 



OF MAIZE OR INDIAN CORN. 



titles. It is probable, however, that the nitrogenous constituents of rice 
are stated too low in the analyses of Braconnot, and that it contains albu- 
men or casein, or some analogous substance, which has been passed over 
by this chemist. A series of carefully repeated analyses of different 
varieties of rice, if it did not modify, would at least fix our present opin- 
ions in regard to its theoretical value as food for man.* 

Two samples of rice examined by Braconnot, were found by him to 
be composed of— 

Carolina. Piedmont. 

Water .... 5-0 7-0 

Husk .... 4-8 4-8 
Gluten .... 3-6 3-6 

Starch .... 85-07 83-8 
Sugar .... 0-3 0-05 

Gum .... 0-7 0-1 

Oil 0-13 0-25 

Phosphates . . 0-4 0-4 

100 100 

2°. Maize or Indian corn is celebrated for the large return of food 
which it yields from a given extent of land, and for its remarkably fat- 
tening qualities when given to poultry, pigs, and cattle. Buckwheat 
is also a very nourishing grain. They consist respectively of — 

Dry maize (Payen). Buckwheat (Zenneck). 

6-0 26-9 

1-2 10-7 

7-1 52-3 

0-5 8-3 

8-9 0-4 

5-05 — 

1-8 ? 



Husk 

Gluten, &c. 

Starch 

Sugar and gum 

Fatty matter 

Colouring matter 

Salts 



24-53t 98-6 

The above analysis of maize must be incorrect, as it supposes the fatty 
matter to amount to nearly 36 per cent, of the weight of the com. 
Dumas has lately stated it at 8-9 per cent. — instead of 8'9 in 24-55 parts, 
as found by Payen — and Liebig denies that Indian corn contains more 
than 5 per cent, of fatty matter. New analyses, therefore, are required 
of this grain also. Indeed it may be said in general of all the substances 
used, especially in feeding animals, that we have not yet the requisite 
knowledge to enable us to reason accurately in regard to the special ope- 
ration of each in sustaining the body or in promoting the growth of fat.J 

* Five varieties of rice, as it is sold in the shops, examined in my laboratory, lost of water 
and gave of ash per cent, respectively — 

Water. Ash. Water. Ash. 

Madras rice .... 135 0-58 Carolina rice . . . 130 033 

Bengal rice .... 131 0-45 Do. flour . . 14-6 0-35 

Patna rice .... 13-1 036 

The water in these samples is very much greater than in those examined by Braconnot. By 
exposure to the air the rice in a few days re-absorbed nearly all it had lost by drying. The 
ash of rice contains more alkaline matter than that of wheat, and is very diflBcult to burn white. 

t Dumas, Traite de Chimie, vi., p. 394. 

t A sample of Indian corn examined in my laboratory, lost of water 13-6 per cent., and 
left of white earthy ash 1-3 per cent. 



GENERAL EFFECT OF MANURES. 513 

§ 18. On the alleged general effect of different manures in modifying the 
amount of gluten and albumen in ivheat, barley, oats, and rye. 

Among the general deductions in regard to the special influence of 
manures upon the quality of the grain we reap, that which has been re- 
ceived with the greatest confidence is this — that the richer in nitrogen the 
manure we apply, the richer in gluten the grain we reap. 

The only experiments, having any pretensions to accuracy, by which 
this opinion has hitherto been supported, are those of Hermbstadt. The 
results of these experiments are contained in the four tables to which I 
have directed your attention under the heads of wheat, barley, oats, and 
rye. As the opinion founded upon them is one which, if correct, is of 
great practical value, — it will be proper to examine the experiments them- 
selves a little more narrowly. Are they really deserving of implicit 
credit ? Do they justify the conclusion that has been drawn from them ? 

Turn first to the experiments upon wheat, of wliich the results are 
embodied in the following table, repeated from page 603 : — 

« '<=- . M . ro . oj . g . . 5 fc (ina 

J-. <utB .-' ^t> aSi to to gho b-boajtuS a a 

fci-J <D a ««c 50 !-c Si, c Pa bt-s 5 » C 

,9 3 



OS SS S cc-o CS-a Mb W-o Pu-a O-a ►> S (5 a 

Return Hlold. 14 fold. 12 fold. 12fold. 12 fold. lOfold. 9fold. 7fold. 5 fold. 3fold. 

Water 43 4-2 4-2 43 42 4-3 43 4-2 4-2 4-2 

Gluten 34-2 33-9 32-9 32-9 351 13-7 122 12-0 9a 9-2 

Albumen 1-0 1-3 1-3 13 ]-4 11 09 10 08 0-7 

Starch 41-3 414 42-8 42-4 399 61-6 63-2 623 659 66-6 

Sugar 1-9 1-6 r5 1-5 1-4 1-6 1-9 1-9 1-9 1-9 

Gum 1-8 1-6 1-5 1-5 1-6 1-6 1-9 1-9 1 G 18 

FattyOil 09 Tl 10 0-9 10 \0 09 1-0 I'O 10 

SolublePhosphates,&c. 05 0-6 0-7 07 0-9 0-6 05 6 05 03 

Husk and bran 139 14-0 138 14-2 14-2 14-0 14-0 149 14-0 14-0 

99-8 99-7 99-7 997 99-7 99-6 99-8 99-7 99-8 99-7 

1°. Water present. — The water in each of these 10 specimens of grain 
was nearly the same, about 4^ per cent. I have already stated the quan- 
tity of water in English flour to amount to about 16 per cent, on an ave- 
rage. Many samples of wheat also have been dried in my laboratory. 
From the results I extract the following, showing the water lost by corn 
grown in four different parts of the world : — 

English, Lammas red 15*1 per cent. 

Seminoff wheat 13-2 *' 

St. Petersburg 16-1 " 

Burletta wheat 13-1 " 

This weight of water is lost when the grain, as it is sold in the market, 
is crushed and then heated to a temperature not exceeding 220° as long 
as it loses weight. 

The above quantities of water are very much greater than those found 
in the wheats of Hermbstadt. I cannot offer these results, however, as a 
j^roq/" of inaccuracy on the part of this experimenter, as I have not had 
access to his original memoir. It is only fair towards him, therefore, to 
conclude that, before they were subjected to analysis, his wheats had been 
artificially dried in a very considerable degree. 

2°. Oil in the different samjjles. — Again, it appears remarkable that 
the quantity of oil in all the samples of wheat in the above table is nearly 
identical, and is also very small. I have examined the fine flour yielded 
by several samples of the same wheat, grown by Mr. Burnet, of Gad- 



514 OIL lis DIFFERENT SAMPLES OF WHEAT. 

girth, ui>on the same field, but dressed with different manures, [Appen- 
dix, pp. 55 and 71,] and the proportions of oil which they yielded in 
the state in which they came from the mill, were as follows : — 

Per cent. 

1°. From the undressed soil 1'4 

2°. Dressed with guano and wood-ash 1*9 

3°. With artificial guano and wood-ash 2*2 

4°. Sulphated urine and wood-ash 2*2 

5°. Do. do. and sulphate of soda 2*0 

6°. Do. do. and common salt 2*7 

7°. Do. do. and nitrate of soda 2-3 

The two facts — that the quantity of oil in nearly all the above sam- 
ples is so much greater than was found by Hermbstadt in any of his 
specimens, and that the proportion varied with the kind of manure with 
which the wheat had been dressed — these two facts, I think, show that 
the analyses of Hermbstadt have not been made with such a degree of 
accuracy as to justify us in relying with confidence upon the general de- 
ductions to which they seem to lead. 

3°. Relative effects of these manures upon different crops. — If we com- 
pare together the relative proportions of gluten and albumen contained in 
the several samples of wheat, barley, oats, and rye, examined by 
Hermbstadt, and exhibited in his tables, we shall find that the effects of 
his manures were by no means unifo'm upon the several crops. Thus, 
when manured with — 

The gluten and albumen per cent, 
taken together were in the 
Kind of Manure. Wheat " " ' " 

Ox blood .... 35-2 



•I 



Night soil . 
Sheep's dung 
Human urine 
Horse dung 
Pigeon's dung 
Cow dung . 
Nothing 

Upon the numbers in 



Barley. 


Oats. 


Rye. 


61 


5-4 


15-6 


6'3 


50 


151 


61 


45 


15-3 


6-4 


49 


15-5 


61 


45 


14-7 


60 


3-5 


15-3 


3-5 


3-4 


12-8 


30 


21 


11-2 



352 
342 
36 5 
14-8 
131 
130 
9-9 

this table I offer you the following remarks : — 
a. Upon the wheat, the effect of the horse and pigeon's dung, in in- 
creasing the amount of gluten and albumen, was little more than one- 
fifth of that produced by the sheep's dung. Thus the wheat contained 
of gluten and albumen, — 

Per cent. Increase of gluten. 

Undressed 9-9 — 

With sheep's dung . . . 34-1 24-2 per cent. 

With horse dung .... 14*7 4*8 

With pigeon's dung . . . 13-1 3-2 

But we have seen (p. 470) that in so far as the nitrogen is concerned, 
dry horse and sheep's dung ought to produce equal effects, while pigeon's 
dung should have three times the effect of either.* Whatever be the 
cause of the increased proportion of gluten in the experimental wheats 
of Hermbstadt, it cannot, therefore, have been owing solely to the pro- 
portion of nitrogen in the manures he applied . 

• 22 of dry pigeon's dung are equal to 65 of sheep's, or 64 of horse's dung. 



DIFFERENT PROPORTIONS OF GLUTEN. 515 

b. Again, upon the barley, oats, and rye, the sheep's dung produced 
little more effect than the horse's dung. It might be said that this was 
because these two manures contain nearly the same proportions of nitro- 
gen. But if so, why did they not produce like effects also upon the 
wheat ? — and why did pigeon's dung impart less gluten than either, to 
all these varieties of grain ? 

c. The unsatisfactory nature of these experiments is still more clearly 
seen when we compare the relative proportions of nitrogen, contained in 
the several manures applied, with the proportions of the same element 
contained in the several crops to which these manures had been added. 

This comparison is made in the following table — the quantity of nitro- 
gen in sheep's dung and in the crops manured with it being called 
100 :— 

Proportions of Proportions of nitrogen added to the 
Manure applied. ^iTSnl crop by each manure.- 

Wheat. Barley. Oata. Rye. 
Sheep's dung ... 100 100 100 100 100 

Horse dung ... 102 16 75 100 66 

Pigeon's dung . . 300 9 48 43 55 

Cow dung ... 97 6 1 66 22 

The relation which exists among the numbers in the first of the above 
columns, is totally unlike that which exists among those in any of the 
others. In none of the crops does the quantity of nitrogen in the manure 
hear a perceptible relation to that contained in the grain that was reaped. 

The theory, therefore, that the quantity of gluten in the crop is always 
determined by that in the manure, and that the amount of gluten in the 
grain we reap may at pleasure be increased by the use of manures 
which are rich in nitrogen — this theory derives in reality no solid support 
from the experiments of Hermbstadt. The theory may indeed be correct, 
but it is not sustained by any rigorous experiments hitherto made — and 
the prudent man will place little reliance upon it, until its correctness 
shall have been proved by future and more rigorously conducted investi- 
gations. 

§ 19. Composition of peas, beans, and vetches. 

The seeds of leguminous plants in general contain a large quantity of 
a substance — very analogous to the gluten of wheat — to which the name 
of legumin has been given. 

To extract this legumin, bruised beans, peas, or vetches, are steeped 
in tepid water for some hours, then rubbed to a pulp in a mortar with 
their own weight of warm water, and, after an hour, strained through 
linen. The strained liquid deposits, at first, a quantity of starch, but is 
obtained nearly clear by filtration. To the filtered solution diluted 
acetic acid (vinegar) or sulphuric acid is added in small quantity, when 
the legumin coagulates and falls in the form of nearly insoluble flocks, 

* These columns are calculated by multiplying together the increase of crop and the in- 
crease in the per cenfage of gluten and albumen. Thus in (he case of wheat — 

Increase of crop. Increase of gluten. Product. Proportions. 

Sheep's dung 9 fold X 24 -3 per cent. = 2187 = 100 

Horse dung 7 fold X 49 per cent. = 34-3 = 16 

Pigeon's dung 6 fold X 32 per cent. = 192 = 9 

Cow dung 4 fold X 3 1 per cent. = 12 4 = 6 

29* 



516 COMPOSITION OF PEAS, BEANS A>D liENTILS. 

which are easily collected on a filter. The addition of an excess of acid 
will re-dissolve the coagulated leguniin, which is again thrown down by 
a few drops of a solution of carbonate of soda or of ammonia ; a slight 
excess of either of the latter, however, will cause the precipitate a second 
time to disappear. The legumin of the pea and bean, therefore, differs 
from the gluten of wheat, in being soluble in water (Dumas), and in very 
dilute acid or alcaline solutions. 

The solution of legumin in water is coagulated when heated nearly to 
boiling, in which respect it resembles albumen (white of egg), and it is also 
coagulated by rennet, in which, and in its relations to acids and alcalies, 
it resembles casein, the curd of milli. Legumin has, indeed, by Liebig, 
been called vegetable casein, from an impression that it is identical in 
composition and properties with the pure curd of millv. 

The semi-transparent solution of legumin in water, obtained directly 
from beans or peas, gradually beconies opaque, and slowly deposits the 
legumin in an insoluble state. This is owing to the production of a 
small quantity of acid by the decomposition of the sugar or other sub- 
stances present in the liquid. This acid slowly coagulates the legumin 
in the same way as when dilute acids are artificially added to the solu- 
tion. It is proper to mention that other chemists consider legumin, like 
casein, [see the following lecture,] to be nearly insoluble in water, and 
that in the solutions from the bean and the pea it is rendered soluble by 
the presence of a little potash, soda, or lime — the liquid becoming turbid 
as soon as a quantity of acid is formed to combine with these alcaline 
substances. According to Dumas, pure legumin dried in vacuo at 284° 
F. consists of — 

Fibrin 
Legumin. of 

V^^heat 

Carbon 50'4 53-23" 

Hydrogen .... 69 701 

Nitrogen .... 18-2 16-41 

Oxygen, sulphur, & 
phosph 24-5 23-35 



Albumen 


Glutine 


Casein 


of 


of 


of 


Wheat. 


Wheat. 


Wheat. 


53-74 


53 05 


53-46 


711 


7-17 


713 


15-65 


15-94 


1604 


23-50 


23-84 


23-37 



100 100 100 100 100 

For the purpose of comparison, I have inserted the composition, ac- 
cording to the same chemist, of the several nitrogenous compounds ex- 
isting in wheat. 

If these analyses be correct, legumin contains more nitrogen than the 
fibrin, the albumen, the glutine, or the casein of wheat, and is almost 
identical with the gelatine of bones. The important consequence deduced 
from this fact, by Dumas, in reference to the feeding of animals, we shall 
consider in a subsequent lecture. 

Above, I have given the composition of legumin, the nitrogenous 
principles contained in peas and beans, as found by Dumas, from which 
it would appear to contain more nitrogen than any of the other vegetable 
principles hitherto found in cultivated grains. The legumin analysed by 
Dumas was extracted from sweet almonds. 

Since the preceding sheet was prepared for press, a further analysis of 
legumin, extracted from beans, has been published by Rochleder,* which 

* Armalen der Ohem. et Pharnuu^ie, jclvj., p. 155. 



ANALYSIS or LEOUMI?r. M7 

does not agree with that of Dumas, but represents this legumin as iden- 
tical with casein, the curd of milk (see the following lecture), and as dif- 
fering in properties as well as in composition from that of the almond. 

The legumin of beans and peas is soluble in cold water, and the solu- 
tion, upon evaporation, forms a skin on the surface which is renewed as 
often as it is removed. It is not coagulated by boiling, but is immediately 
thrown down in fine flocks by acetic acid, which, when added in excess, 
does not redissolve it (Liebig). 

The legumin from sweet almonds is also soluble in cold water, but, 
like albumen, falls in flocks when the solution is heated nearly to boil- 
ing. It is precipitated also by diluted acetic acid, and is again dissolved 
when an excess of this acid is added (Dumas). 

The two substances, therefore, are different in their properties. Their 
constitution is represented respectively by — 

LEGUMIN FROM 

Beans Sweet almonds 

(Rochleder). (Dumas). 

Carbon .... 54-5 60-4 

Hydrogen .... 7-4 6-9 

Nitrogen .... 14-8 18-2 

Oxygen .... 23-3 24-5 

100 100 

When we come to consider the feeding of animals, we shall find that 
this difference in the composition of the two varieties will materially af- 
fect the view we must take in regard to the action of each in contributing 
to the support of the various parts of the animal body. 

The approximate composition of the entire peas and beans is thus 
stated by Einhof. [Zierl Kncyclopcedie, ii., p. 52]. 

Composition of the grain. Composition of the meal. 

Water. Husk. Meal. Starch. Legumin. Gum,&c. 

Peas 140 105 755 650 23 12 

Field Beans . . . 155 162 683 690 19 12 

A series of rigorous analyses of the seeds of leguminous plants is at 
present much to be desired. According to those of Braconnot and Einhof, 
certain species examined by them consisted of — 

Kidney Field beans, Lentils, 
Peas. beans. (Einhof.) dried* 

(Einhof) 

Water • 125 230 15*6 

Husk 8 3 70 100 18-7 

Legumin, albumen, &c. . 26-4 23-6 11-7 38*5 

Starch 43-6 430 50-1 32-8 

Sugur 20 0-2 q.„ 3-1 

Gum, &c 40 1-5 ^^ 60 

Oil and fat 1-2 0-7 1 1 

Salts and loss .... 20 1-0 4*4 09 

1000 1000 1000 lOOOt 

These analyses agree in showing that the seeds of leguminous plants 

• By drying, the lentils lost 14 per cent, of water. 

t Dumas Traite de Chimie, vi. p. 307, comparad with Thomson's Vegetable Chemiatryt 
p 884, Schubler's AgriouUur Ckemie, il., p. 194, and Sprengel's Chetnie fur Landairth*^ a., 
p. 368. 



518 EFFECT OF SOILS AND MANURES UPON PEAS. 

are especially rich in substances containing nitrogen (legumin and albu- 
men), and are therefore fitted to contribute much to the nourishment of 
those animals which, in consequence of the state of their growth and 
health, or the purposes for which they are reared and maintained, require 
a large supply of this important element. 

§ 20. Effect of soils and manures upon the quality of peas and beans. 

The quality of the seeds of leguminous plants is also affected by the 
mode of culture to which they are subjected, and by the kind of soil in 
which they are raised. 

1°. Effect of animal manures. — The dung " of sheep or horses has 
been found to impart a better flavour to the pea, and to render the husk 
thinner than when that of hogs or oxen has been used." [British Hus- 
bandry, ii., p. 217.] 

2°. Effect of mineral manures. — The effect of gypsum and of other 
sulphates upon leguminous plants is universally known (p. 482.) The 
beneficial influence of a mixture of gypsum and common salt upon 
sickly crops of beans and peas is very strikingly displayed in the inter- 
esting experiments of Mr. Alexander, of Southbar, to the details of which 
1 have already had occasion to draw your attention. [See Appendix, p. 
217.] 

3°. Effect of lime. — Dr. Anderson says, " that the pea cannot be 
reared to perfection in any field which has not been either naturally or 
artificially impregnated with some calcareous matter," but that " a soil 
which could hardly have brought a single pea to perfection, although 
richly manured with dung, if once limed, will be capable of producing 
abundant crops of peas ever (?) afterwards, if duly prepared in other re- 
spects." [Essays, ii., p. 302.] 

4°. Boiling or melting quality of peas. — But the most singular cir- 
cumstance in connection with this class of seeds, to which the agiicul- 
tural chemist has hitherto been directed, is the property possessed by 
peas and beans of boiling soft or mouldering into a pulp more or less 
easily, according to the kind of land in which they are raised or to the 
species of manure with which they are dressed. The observations, 
however, which I have found upon record in reference to this point are 
of a contradictory character. Thus — 

a. Sprengel says " that peas which are raised after liming or marling 
boil sojt more easily, and are more agreeable to the taste than when raised 
after manure." [Die Lehre vom Diinger, p. 297.] 

b. A French authority, on the other hand, quoted by Loudon, [Ency- 
clopaedia of Agriculture, p. 837,] says, tliat " stiff land or sandy land 
that has been limed or marled, or to which gypsum has been applied, 
produces peas that will not melt in boiling, no matter what the variety 
may be. The same effect is produced on the seeds and pods of beans 
and of all leguminous plants. To counteract this fault in the boiling, it 
is only necessary to throw into the water a small quantity of the com- 
mon soda of the shops." 

c. The author of the British Husbandry, [ii., p. 217,] says, "that 
shell marl or lime is found to forward this crop more than any other 
mineral manure, though it is said to communicate a degree of hardness 
to the grain which renders it unfit for boiling." 



SOME PEAS REFUSE TO BOIL SOFT. 519- 

Independently of all applications to the soil, I believe it is generally 
observed that good boilers are produced upon light, sandy, and gravelly 
soils ; while heavy, wet, undrained (and newly broken up ?) land usually 
produces bad boiling peas and beans. Thus melting peas {sidder peas, 
as they are locally called) for the Birmingham market are grown on the 
slopes of the gravelly hill of Hopwas, two miles from Tamworth, on 
the Lichfield road — the red clay lands of the vale of the Tame produc- 
ing in general pig* peas or beans only. It is on similar soils that melt- 
ing barley and mealy potatoes are produced, and the effect upon the 
three crops may probably be due to a common cause. 

At all events it is probable — 

a. That the boiling quality of the pea crop is not owing to the qual- 
ity of the seed — since peas of both varieties have been raised from the 
same seed.f 

b. That it is not generally owing to the seasons, since some land pro- 
duces hard peas every year. If the wetness of the soil indeed have any 
influence, a rainy season may cause the production of bad boilers upon 
land from which soft peas are usually reaped. 

4°. Chemical difference between the two varieties of pea. — Why does 
one of these varieties of pea melt more readily than the other ? For 
the same reason very nearly that one potatoe boils mealy, and another 
waxy, and that one sample of barley melts better in the mash-tub than 
another. Melting peas and barley and mealy potatoes contain a larger 
proportion of starch than samples which are possessed of an opposite 
quality. 

The pea, as we have seen, consists essentially of legumin and starch. 
The former coagulates and contracts, or runs together into a mass by 
boiling, — the latter, on the contrary, expands, becomes more bulky, tends 
to burst the husk, and to separate into single grains. If the tendency to 
contract and cohere be greater than the disposition to expand and sepa- 
rate — in other words, if the legumin predominate — the pea does not melt, 
while if the starch be abundant the pea boils well. It is possible that 
tlie addition of a little soda may cause hard peas to melt, since legumin 
is soluble in a solution of soda, but in waters impregnated with lime all 
peas are said to boil soft much less readily than in such as are free from 
that ingredient. [Dumas, Traite de Chimie, vi.] 

It is only when peas and beans are raised for the food of man that the 
possession of the melting property becomes a matter of importance. It 
is rather because they are more agreeable to the palate than because they 
are ascertained to be more nutritive, that they are preferred in this state. 
When we come to consider the feeding of stock, we shall see that, ac- 
cording to the present state of our knowledge, the opinion may rea- 
sonably be entertained that insoluble peas are really better adapted for the 
feeding and fattening pigs and other stock — the purpose for which they 
are employed — than those which are possessed of the melting quality. 

It is a difference in the chemical composition of the seeds of legumi- 
nous plants that makes them melt more or less easily — but by what 

* Much used for the feeding of pigs. 

t Some however suppose it to depend upon the age of the seed, or the time of sowing. 
—British Jlttsbandry, ii., p. 217. 



620 C0MP0SITI05 or potatoes. 

quality in the soil or manure is this difference in composition produced 1 
In regard to lime the evidence is contradictory. Gypsum may render 
them harder since legumin contains sulphur, and a portion of the effect 
of gypsum upon leguminous crops is supposed to arise from its yielding 
sulphur to the growing plants, and thus promoting the production of le- 
gumin. Wet and clay lands also favour the production of legumin 
more than that of starch — but in what way, we are not yet in possession 
of experimental results of sufficient accuracy to enable us to say. 

§ 21. Of the co7nposition of potatoes, and the effect of circumstances in 
modifying their cmnposition. 

1°. Composition of potatoes. — Potatoes, in addition to much water, 
consist of starch, gum, woody fibre, and albumen. The proportions of 
these several constituents are veiy variable. Thus, according to 
Einhof and Lampadius, the following kinds of potatoe consisted in 100 
parts of — 

2°. Influence of the state of ripeness. — According to Korte the quan- 
tity of dry solid niatter contained in the potatoe depends y^ry much upon 
the state of ripeness to which it has attained. The ripest leave 30 to 32 
per cent, of dry matter, the least ripe only 24 per cent. The per 
centage of starch varies from 8 to 16 per cent. The mean result of his 
examination of 55 varieties of potatoe gave him for the solid matter 24*9, 
and for the starch 11*85 per cent. [Schiibler, Agricultur Chemie, ii., p. 
213.] 

3°. Influence of variety. — Much appears also to depend upon the 
variety of potatoe. Thus the following varieties of potatoe grown at 
Barrochan in Renfrewshire, in 1842, yielded respectively — 

Connaught cups .... 21 per cent, of starch. 
Irish blacks ..... \6^ •» 

White dons 13 ** 

Red dons lOf ♦♦ 

— while, according to a starch manufacturer in the neighbourhood, 11^ 
per cent, has been the average quantity obtained from the common 
rough red of good quality during the last four years. 

The difference in the quantity of starch yielded by the above-named 
varieties is the more striking wlien taken in connection with the weight 
of each per acre, raised from the same land, treated in the same way. 
These weights were as follows : — 

Containing of 
Manure. Produce per acre. starch. 

Cups, with 4 cwt. of guano 13| tons 2-9 tons. 

RpA Dons, with 4 cwt. of guano \A\ " 1 5 " 

White Done, with 3 cwt. of guano IS^' " 2 4 " 

So that, of these three crops, that of cups, which weighed the least, 
gave the largest produce of starch. It yielded nearly twice as much as 
the red dons, which were half a ton heavier, and one-fifth more than 
even the white dons, the crop of which was greater by five tons an acre. 
Such differences as these, in the relative quantities of starch, which may 
be obtained from an acre of the same land by the growth of different va- 
rieties of potatoe are deserving of the attentive consideration of the prac- 
tical man. 

See Appendix, p. 61. 



THE PROPORTION OF STARCH VARIES VERY MUCH- 521 

Larger quantities of slarch than any of those above stated have been 

obtained from potatoes by some experimenters. Thus from the 

Per cent, of starch. 
Kidney potatoe, Dr. Pearson obtained . . . 28 to 32 

Apple do. Sir H. Davy 18 to 20 

Shaw do. Vauquelin ..... 18'8 

L'Orpheline do. 24-4 

The first and last of these proportions are probably very rare in our 

climate. 

4°. Effect of keeping. — Those potatoes are said to keep best in which 

the starch is most abundant, but in general keeping has an effect — 

a. Oil the 'proportion of starch. — ^By keeping till the spring, potatoes 
lose from 4 to 7 per cent, of their weight, and the quantity of starch they 
are capable of yielding suffers a considerable diminution. Thus, ac- 
cording to Payen, the same variety of potatoe yielded of starch in 

October, 17-2 per cent. January, 15-5 per cent. 

November, 16-8 " February, 15-2 " 

December, 15-6 " March, 15-0 " 

April, 14-5 " 

This diminution is probably owing to the conversion of a portion of the 
starch into sugar and gum. When potatoes are rendered unfit for food 
by being frozen and suddenly thawed, the quantity of starch which they 
are capable of yielding is said to have undergone no diminution. 

b. On the proportion of gluten. — The proportion of gluten also ap- 
pears to become less when potatoes are kept. Thus, in new potatoes' 
Boussingault found the gluten amount to 2|- per cent., but in old potatoes 
to only 1| per cent, of their weight. To this natural diminution of the 
proportion of starch and gluten, is probably to be ascribed the smaller 
value in the feedmg of stock, which experience has shown very old po- 
tatoes to possess. 

5°. Effect of soils and manures. — The potatoe thrives best on a light 
loamy soil — neither too dry, nor too moist. The most agreeably flavour- 
ed table potatoes are almost always produced from newly broken up 
pasture ground, not manured, or from any new soil. [Loudon's Ency- 
clopaedia of Agriculture, p. 847.] When the soil is suitable, they delight 
in much rain, and hence the large crops of potatoes obtained in Ireland, 
in Lancashire, and in the west of Scotland. No skill will enable 
the farmer to produce crops of equal weight on the east coast where 
rains are less abundant. It has not been shown, however, that the weighs 
of starch produced in the less rainy districts is defective in an equal de- 
gree. Warm climates and dry seasons, as well as dry soils, appear to 
increase the per-centage of starch. 

Potatoes are considered by the farmer to be an exhausting crop, and 
they require a plentiful supply of manure. By abundantly manuring, 
however, the land in the neighbourhood of some of our large towns, 
where this crop is valuable, have been made to produce potatoes and 
corn every other year, for a very long period. 

6°. Influence of saline manures, — I have already drawn your attention 
to the remarkable influence of certain saline substances in promoting the 
growth of the potatoe crop in some localities. The most striking effects 
ot this kind hitherto observed in our island haye been produced by mix- 



522 OCCASIONAL FAILURE OF SEED POTATOES. 



1 



tures of the nitrate of soda with the sulphate of soda or with the sulphate 
of magnesia.* The effect of such mixtures affords a beautifal illustration 
of the principle I have frequently before had occasion to press upon youi 
attention — that plants require for their healthy growth a constant supply 
of a considerable number of different organic and inorganic substances. 
Thus upon a field of potatoes, the whole of which was manured alike 
with 40 cart loads of dung, the addition of — 

a. Nitrate of soda alone gave an increase of 3^ tons. 
Sulphate of soda alone gave ... " 
While one half of each gave ... 65- " 

h. Sulphate of ammonia alone gave . . If " 

Sulphate of soda " 

But one half of each gave .... 6| " 

c. Nitrate of soda alone gave .... 3r '* 
Sulphate of magnesia alone gave . . 1 " 
And one half of each gave .... 9| " 

These results are very interesting, and when confirmed by future re- 
petitions of such experiments — and followed up by an examination of 
the quality and composition of the several samples of potatoes produced — 
cannot fail to lead to very important practical conclusions. 

7°. Occasional failure of seed potatoes. — The seeds of all cultivated 
plants are known at times to fail, and the necessity of an occasional 
change of seed is recognised in almost every district. In the Lowlands 
of Scotland potatoes brought from the Highlands are generally pre- 
ferred for seed, and on the banks of the Tyne Scottish potatoes bring a 
higher price for seed than those of native growth. This superior quality 
is supposed by some to arise from the less perfect ripening of the w^- land 
potatoes, and in conformity with this view the extensive failures which 
have taken place during the present summer (1843) have been ascribed 
to the unusual degree of ripeness attained by the potatoes during the 
warm dry autumn of the past year. 

This may in part be a true explanation of the fact, if — as is said — the 
ripest potatoes always contain the largest proportion of starch — since 
some very interesting observations of Mr. Stirrat, of Paisley, would 
seem to indicate that whatever increases the per-centage of starch, in- 
creases also the risk of failure in jwtatoes that are to he used for seed.] 
This subject is highly deserving of further investigation. 

• For the particulars of these experiments see the Appendix. 

T I insert Mr. Stirrat's letter upon this subject, not only because his observations are in- 
tereeting in themselves, but because they are really deserving of the careful attention of 
practical men : — 

"Sir, — The following experiment wilh potatoes was tried with the view Qf eliscovering the 
cause of so many failures in the crops of late years, from the seed not vegetating, and rotting 
in the ground. I had an idea that the vegetative principle of the plant might become weak 
in consequence of being grown on land that had been a long time subjected to cropping, and 
not allowed any length of time to lie at rest. I, therefore, raised a few bolls on land that had 
Iain lea for 70 years (being part of my bleach green), and found that these on being planted 
again the following year were remarkably strong and healthy, and not a plant gave way, and 
I have continued the same method for the last six years, and the result has, in every instance, 
been equally favourable. Four years ago, one boll of my seed potatoes was planted along 
with some others in a field of about an acre, the other seed was grown on the farm, and the 
seed all gave way excepting that got from me. They were all planted at the same time and 



EFFECT OF SALINE SUBSTANCES 523 

8°. Effect of saline top-dressings on the quality of the seed. — ^It may 
be doubted, however, whether the relative proportions of starch are to be 
considered as the cause of the relative values of different samples of seed 
potatoes. This proportion may prove a valuable test of the probable 
success of two samples when planted, without being itself the reason of 
the greater or less amount of failures. With the increase of the starch 
it is probable that both the albumen and the saline matter of the potatoe 
will in some degree diminish, and hoili of these are necessary to its fruit 
fulness when used for seed. 

The value of the saline matter is beautifully illustrated by the obser- 
vation of Mr. Fleming, that the potatoes top-dressed with sulphate and 
nitrate of soda in 1841, and used for seed in 1842,* "presented a remark- 
able contrast to the same variety of potatoe, planted alongside of them, 
but which had not been so top-dressed in the previous season. These 
last came away weak, and of a yellowish colour, and under the same 
treatment in every respect did not produce so good a crop by fifteen bolls 
(3f tons) an acre." This observation, made in 1842, is confirmed by the 
appearance of the crops now growing CJuly, 1843) upon Mr. Fleming's 
experimental fields. The prosecution of the enquiry opened up by his 
experiments promises to lead to the most valuable practical results. * They 
ma^' teach us how to secure at all times a fruitful seed, and thus to dis- 
pense with supplies of imported produce. 

§ 22. The composition of the turnip, tJie carrot, the beet, and the parsnip. 

1°. Composition. — The potatoe is characterised by containing a large 
proportion of starch in connection with a small quantity of albumen — the 
turnip and carrot by containing, in place of the starch, a variable pro- 

with the same manure. From these circumstances, I am of opinion, that if farmers were 
careful in raising Iheirovvn seed potatoes from land that has lain long in a state of rest (a) — or 
where that cannot be had, the same object can be obtained by bringing new soil to tlie sur- 
face by trenching as much as is necessary, or by the use of the subsoil-plough — failures of 
the potatoe crop from the seed not being good, would become much less frequent. I am 
somewhat confirmed in this opinion by the fact, that it has been found for the last dozen of 

{fears that generally the hesi seed potatoes have been got from farms in the moors or high 
ands of the country. The reason of this may be that these high lands have been but of late 
brought under crops of any kind, and many of them but newly brought from a state of nature, 
and the superiority of seed potatoes from these high lands may not at all arise (as is gene- 
rally supposed) from a change of soil or climate. 

" Potatoes raised on new soil, or on ground that has been long lying lea, are not so good 
for the table as the others, being mostly very soft, and, by the following experiment, it would 
appear that they contain a much less quantity of farina than those which are raised from 
land that has been some time under crop, and, perhaps, this is the reason why they arc better 
for seed. From one peck of potatoes, grown on land near Paisley, which has been almost 
constantly under crop for the last 30 years, I obtained nearly 7 lbs. of flour or starch ; and 
from the other peck, grown on my bleach green, the quantity obtained was under 4 lbs., from 
which it would seem that as the vegetative principle of the plant is strengthened, the farina- 
ceous principle is weakened, and vice versa. Jas. Stirrat." 
Paisley, 22d November, 1842. 

(a)Mr. Finnie, of Swanstone, informsme that the growing of potatoes intended forseed upon 
new land, has long been practised by good farmers. Mr. Little, of Carlesgill, near Langholm, 
writes me that in Dumfriesshire, they obtain the best change of potatoe seed from mossy 
land — of oats and barley from the warmer and drier climate of Roxburghshire. The grains, 
he adds, degenerate by once sowing, still looking plump when dry, but having a thicker husk, 
and weighing two or three pounds less per bushel. The deterioration of seeds, in general, 
is a cAemico-physiological subject of great interest and importance, and will doubtles.-; soon 
be taken up and investigated. 

* In the Appendix, p, 47, the experiments are recorded, and in p. 66 I have more fully ad- 
verted to the interesting results likely to be derived from the continuance of such experiments. 



624 COMPOSITION OF THE TURNIP, CARROT, AND BEET. 

portion of sugar, and of a gelatinous gummy-like substance, to which 
the name of pectin has been given. In the Swedish turnip and in beet- 
root the sugar predominates, in the white turnip and in the carrot the 
pectin is usually present in the larger quantity. 

The composition of the turnip, the carrot, and the beet varies very much, 
and is influenced by a great variety of circumstances. We are not in 
possession of any recent detailed analyses of these roots. The following 
table exhibits the component parts of several varieties, as they have been 
given chiefly by Hermbstadt, [Schlibler, Ag. Chera., ii., p. 207] :— 





Variety of Turnips. 




Sugar 












Common 
Carrot. 


beet 
(Payen). 


Parsnip 
(Crome), 




White. 


Swedish. 


Cabbage. 


Water . . . 


, 79-0 


800 


78-0 


80-0 


85-0 


79-4 


Starch and fibre 


. 7-2 


53 


60 


90 


30 


6-9 


Gum (pectin ?) 


. 2-5 


30 


3-5 


1-7& 


20 


6-1 


Sugar . . . 


. 8-0 


90 


90 


7-8 


100 


55 


Albumen . . 


. 2-5 


20 


2.5 


M 


7 


21 


Salts .... 


. 0-5 


0-5 


05 





7 


'I 


Loss .... 


. 0-3 


0? 


05 


oil 35 


— 


— 




100 


100 


100 


100 


100 


100 



These analyses are very defective, and apply with any degree of cor- 
rectness only to the specimens actually operated upon. Any reasonings, 
therefore, which are founded upon them can only lead to probable or ap- 
proximate conclusions. 

2°. The proportion of sugar contained in the sap of these roots is 
greatest when they are young, and diminishes as they ripen. In the 
beet, it has been observed that the nitrates of potash and ammonia are 
present in considerable quantity, and that in the old beet these nitrates 
become more abundant as the sugar diminishes. In the beet, also, when 
raised by the aid of rich manure, the production of nitrates is increased 
more than that of sugar.* The same may possibly be the case with the 
common cultivated turnips. It would not be without interest, both theo- 
retically and practically, to ascertain by experiment, the relative com- 
position of the same variety of turnip, grown on the same soil, by the 
aid of rich farm-yard manure, and by the aid of bones or of rape-dust. 
The one may produce more sugar, the other more albumen or nitrates. 
Such differences may materially affect the value of the crop, either in 
the feeding of stock or in the production of an enriching manure. It is 
in suggesting and carrying on enquiries of this kind that the joint labours 
of the practical farmer and of the theoretical chemist are likely, among 
other ways, to promote the advancement of a rational and scientific agri- 
culture. 

3°. Effect of soils and manures. — These roots delight in a rich, open, 
and loamy soil — and the weight of produce varies nuich with the kind 
of manure that may have been applied to them. [See, for many in- 
structive illustrations of this fact, the experiments upon turnips, detailed 
in the Appendix, pp. 43 et seg.] No experiments, however, have yet 
been made to determine the relative proportions of water and of their 
other constituents which the same turnips contain, when raised by the 

" According to Payen, the beet, when raised with street manure, contains 20 times ai 
much saltpetre as when raised in the ordinary manner. 



•WATER PER CENT. 


DRY MA 


TTER PI 


!R CENT. 


Einhof. Playfair. Hermb- 


Einhof. Playfair. 


Hermb- 

atadt. 


93 89 79 


8 


11 


21 


87i 85 80 


12i 


15 


20 


86 — 78 


14 


— 


23 


white. 








86 87 80 


14 


13 


20 



WATER IN DIFFERENT VARIETIES OF TURNIP. 525 

aid of different manures, nor, consequently, the true effect of these 
manures upon the relative values of the several crops. 

4°. Quantity of water in different varieties of turnip. — The same re- 
mark may be made in regard to the several varieties of turnip. All 
those examined by Hermbstadt, as appears from the above tables, con- 
tained 20 to 22 per cent, of solid matter (78 to 80 of water), while other 
experimenters have found as little as from 8 to 15 of solid matter in tur- 
nips, and generally less in the white and large globe turnip than in the 
yellow and more solid Swede. 

Thus, four varieties of the above roots contain of water and solid mat- 
ter, according to three different experimenters : — 



White turnip 
Swedish do. 
Cabbage do. 

Carrot . . 

The above differences are very great, especially when we look to the 
relative proportions of dry matter in which the nutritive power resides. 
They are of much importance, therefore, to the feeding of stock, and 
the circumstances under which they occur, are deserving of a careful in- 
vestigation. 

5°. Relative nutritive properties of the potatoe and the turnip. — The 
potatoe is usually considered more nutritive than the turnip, weight for 
weight, and no doubt it generally is so. But if we compare together the 
piantities of solid matter w^hich the two roots may contain, we shall see 
how very far wrong our estimate may be in any special case. Thus — 
The turnip contains of solid matter from 8 to 22 per cent. 

The potatoe do. do. 24 to 32 " 

—so that, while the driest turnips may contain four times as much solid 
matter as the most watery potatoes, very dry potatoes may contain 
nearly as much as very juicy turnips. It is impossible, therefore, with- 
out an actual examination of the samples, to pronounce upon the relative 
amount of food which is likely to be contained in any equal weights of 
turnips and potatoes. The very discordant estimates which different 
feeders of stock have formed in regard to the relative value of these 
crops in the production of beef or mutton is partly owing to this cause. 
[Other causes for these discordant estimates will be stated in Lecture 
XXI.] Until the effects of equal weights of the different kinds of food, 
estimated in the dry state, are carefully ascertained, it will be impossible 
to obtain results of a general kind or upon which any real confidence 
can be placed. 

§ 23. Of the composition of the green stems ofpeas, vetches, clover, spurry, 

and hucTc-wheat. 
The stems and leaves of plants which are given as green food to 
animals differ much in composition, according to the age they have at- 
tained, to the rapidity of their growth, to the nature of the soil, the 
season, and the mode of culture. They are generally supposed to be 
richest in nutritive matter when the plant has just come into flower: 



526 COMPOSITION OF THE GREEN STEMS OF PEAS, ETC. 

THie following table exhibits the approximate composition of the 

feen stems of some clovers and vetches, as they have been given by 
inhof and Crome : — 

t» _ 

O _ is ,-) 





P..S 

SB 


o S 

2^ 


-38 

0)0 


S 
So 

03 — / 




en stalks 
k-wheat 
(CromeO 


Eu 

6 


27 

a a 

si 


li 

®o 




2 

C5 


P4 


1 


3 


3 

m 


OB3 




A 
^ 


Water . 


800 


760 


800 


750 


77-0 


82-5 


77-5 


79-5 


860 


Starch . 


3-40 


1-4 


10 


2-2 


23 


4-7 


26 


3-8 


1-3 


Woody fibre . 


10-31 


13-9 


11-5 


14-3 


120 


100 


10-4 


11-5 


70 


Sugar 


4-55 


21 


1-5 


0-8 


— 


— 


— 


— 


— 


Albumen 


0-90 


20 


15 


1-9 


2-3 


0-2 


1-9 


0-7 


1-8 


Extractive matter and 




















gum . 


065 


35 


34 


44 


52 


2-6 


76 


3-6 


2-9 


Phosphate of lime . 


019 


10 


0-8 


0-8 


0-8 


1 


— 


— 


— - 


Wax and Resin 


— 


01 


0-2 


0-6 


-2 


h 


1 


0-9 


10 



100 100 99-9 100 99-6 100 100 100 100 

§ 24. Of the composition of the grasses when made into hay. 

1°. An elaborate examination of the grasses of this country, in tlie 
dry state, with the view of determining their relative nutritive proper- 
ties, was made by the late Mr. Sinclair, gardener to the Duke of Bed- 
ford. His method was to boil in water equal weights of each species of 
hay tUl every thing soluble was taken up, and to evaporate the solution 
to dryness. The weights of the dry matter thus obtained he considered 
to represent the nutritive values of the grasses from which the several 
samples of hay were made. 

The results of Mr. Sinclair, liowever, have lost much of their value, 
since it has been satisfactorily ascertained — , 

a. That the proportion of soluble matter yielded by any species of 
grass, when made into hay, varies not only with the age of the grass, 
when cut, but with the soil, the climate, the season, the rapidity of 
growth, the variety of seed sown, and with many other circumstances 
which are susceptible of constant variation. 

h. That animals have the power of digesting a greater or less propor- 
tion of that part of their food which is insoluble in water. Even the 
woody fibre of the hay is not entirely useless as an article of nourish- 
ment — experiment having shown that the manure often contains less 
of this insoluble matter than was present in the food consumed.* (Spren- 
gel.) 

c. That some of the substances which are of the greatest importance 
in the nutrition of animals — such as vegetable fibrin, albumen, casein, 
and legumin — are either wholly insoluble in water or are more or less 
perfectly coagulated and rendered insoluble by boiling with water. Mr. 
Sinclair, therefore, must have left behind, among the insoluble parts of 

* This will not appear surprising when it is recollected that, by pi'olonged digestion in 
diluted sulphuric acid, insoluble woody fibre may be slowly changed into soluble gum or 
sugai- (see p. 112). The proportion of the woody fibre which will be thus worked up in the 
stomach of an animal will depend, among other circumstances, upon the constitution of the 
atiimal itself, upon the abundance of food supplied to it, and upon the more or less perfect 
mastication to which the food is subjected. 



WOOD? FIBRE AND GLUTEN IN THE GRASSES. 627 

his hay, the greater proportion of these important substances. Hence, 
the nature and weight of the dry extracts he obtained could not fairly re- 
present either the kind or quantity of the nutritive matters which the 
hay was likely to yield when introduced into the stomach of an animal. 

For these reasons I do not think it necessary to dwell upon the results 
of his experiments.* 

2°. Woody fibre in the grasses. — In the stems of the grasses (in hay 
and straw), woody fibre is the predominating ingredient. They are not 
destitute of starch, gum, and sugar, but they are distinguished from all 
the other usual forms of animal food, by the large quantity of woody 
fibre, and of saline or earthy matter which they contain. The propor- 
tion of woody fibre in the more common grasses, in their usual state of 
dryness when made into hay and straw, is thus given by Sprengel (see 

Per cent. Per cent. 

Wheat straw, ripe .... 52 Pea straw, ripe 30 

Barley straw, do 50 Bean straw, do 51 

Oat straw, do 40 | Vetch hay, do 42 

Rye straw, do 48 Red clover, do 28 

Indian corn, do 24 Rye grass, do 35 

The proportions of woody fibre here given, however, can be considered 
only as approximations. The riper the straw or grass, the less soluble 
matter does it contain, and every farmer knows how much soil, season, 
and manure, affect the quality of his artificial grasses. One field will 
grow a hard wiry rye-grass, while another will produce a soft and flexi- 
ble plant, and a highly nutritious hay. 

3°.^ Gluten in the grasses. — Boussingault, who considers the relative 
nutritive value of the vegetable substances employed for fodder to be in- 
dicated by the proportions of nitrogen they severally contain, has arranged 
grass and clover hays and the straws of the corn plants, in their usual 
state of dryness, in the following order : — 

Or pluten, Equal effects 
Nitrogen &c., should be 

per cent per cent. produced by 

Hay from mixed grasses i j'J^ ^^^ i 100 lbs. 

Do. aftermath . . . 1-54 93 75t " 

Do, from clover in flower 15 93 75 " 

Pea straw . . . . 195 12-3 64t " 

101 6-4 114 " 

0-54 3-4 240 " 

— — 520 " 

— — 520 " 

— — 550 " 

We shall have occasion to compare the above theoretical values 
{equivalents) assigned to the several kinds of fodder, with the results of 

. J ?'!'^T7''" ^-^ ^","'? ?' ^^"^'^ '" *^6 Appendix to Davy's Agricultural Chemistry, or in a 
tabulated form in Schubler's Agricultur Chemie, ii., p. 208. 

t It is usually supposed that the aftermath is not so valuable as the first produce. Schwertz, 
however, considers it more nourishing by one-tenth part. 

:t "The value of all straw for fodder must depend on (he mode in which it is harvested. 
In Scotland, the order in which the farmer places his straw for fodder is— 1st, pea ; 2nd, 
bean ; 3d, oat ; 4th, wheat ; 5th, barley. While in England, where the bean is quite withered 
before it :s cut, U stands last in the scale,"— Mr. Hyett, Rotfol AgriculturalJoumal, iv.,p. 148 



Lentil straw 
Indian corn straw 
Wheat straw 
Barley straw 
Oat straw . 



528 COMPOSITION OF HEMP AND LINT SEEDS. 

practical experience, when we come to direct our attention more parti- 
cularly to the feeding of stock. 

4°. Fatty matter in the grasses. — Besides woody fibre, starch, gum, 
and gluten, dry hay and straw contain also a variable proportion of fatty 
matter. According to Liebig, it does not exceed 1-56 per cent, in hay, 
while, according to Dumas and Boussingault, as much as 3, 4, or even 5 
per cent, of fat can be extracted from it. To this fact we shall also re- 
turn when considering the methods of fattening stock. 

5°. Inorganic matter in the grasses. — The proportion of saline and 
earthy matter contained in the grasses is an important feature in their 
composition. This, as I have already said, is much larger than in any 
of the other kinds of food usually given to animals, being seldom less 
than 5, and occasionally amounting to as much as 10 per cent, of their 
weight when in the state of hay or straw. A large proportion of the ash 
left by the stems of the corn plants, and by many grasses, consists of 
silica. The straw of the bean, pea, and vetch, and the different kinds 
of clover hay, contain little silica, its place in these plants being supplied 
by a large quantity of lime and magnesia. 

§ 25. Of hemp, line, rape, and other oil-bearing seeds. 

The oily seeds are important to the agriculturist from their long ac- 
knowledged value in the feeding and fattening of cattle. Lintseed is ex- 
tensively used for the latter purpose, both in its entire state and in the 
form of cake — when the greater part of the oil has already been expressed 
from it. All these seeds, however, are not equally palatable to cattle. 
Some varieties they even refuse to eat. Among these is the rape-seed, 
from which so much oil is expressed, and the cake left by which is now 
so extensively employed as a manure. 

These seeds are distinguished from those of the corn plants, by con- 
taining, instead of starch or sugar, a predominating proportion of oil; and 
instead of their gluten a substance soluble in water, which possesses many 
of the properties of the curd of cheese {casein). 

We are in possession of a somewhat imperfect analysis of hemp seed 
and of the seed of the common lint, according to which the varieties ex- 
amined consisted in 100 parts of — 

Hemp seed Lime seed 

(Bucholz). (Leo Meier). 

Oil . ' 19-1 11-3 

Husk, &c 38-3 44-4 

Woody fibre and starch . .5-0 1'5 

Sugar, &c 1-6 10-8 

Gum 9-0 7-1 

Soluble albumen (Casein?) . 24-7 15-1 

Insoluble do — 3-7 

Wax and resin .... 1-6 3-1 

Loss 0-7 3-0 

100 100 

These analyses show that, besides the oil, these seeds contain consi- 
derable proportions of gum and sugar and a large quantity of a substance 
here called soluble albumen, of which nitrogen is a constituent part, but 





Oil per cent. 


Sun-flower seed . 


. . 15 


Walnut kernels . . 


. 40 to 70 


Hazel-nut do. 


. . 60 


Beech-nut do. 


. . 15 to 17 


Plum stone do. . 


. . 33 


Sweet almond do. 


. . 40 to 54 


Bitter do. do. 


. . 28 to 46 



PROPORTION OF OIL IN DIFFERENT SEEDS. 529 

which differs in its properties from the gluten and albumen of the seeds 
of the corn-bearing plants, and has much resemblance to the curd of 
milk. Besides their fattening properties, therefore — which these seeds 
probably owe in a great measure to the oil they contain — this peculiar 
albuminous matter ought to render them very nourishing also ; — capable 
of promoting the growth of the growing, and of sustaining the strength 
of the matured, animal. 

The quantity of oil contained in different seeds of this class, and even 
in the same species of seed when raised in different circumstances, is 
very variable. These facts will appear from the following table, which 
represents the proportions of oil that have been found in 100 lbs. of some 
of the more common seeds : — 

Oil per cent. 

Line seed 11 to 22 

Hemp seed 14 to 25 

Rape seed 40 to 70 

Poppy seed . . . . 36 to 53 
White mustard do. . . 36 to 38 
Black do. do. . . 15 
Swedish turnip do. . . 34 

It seems to be a provision of nature, that the seeds of nearly all plants 
should contain a greater or less proportion of oil, which is lodged for the 
most part in, or immediately beneath, the husk, and, among other pur- 
poses, may be intended to aid in preserving the seed. We shall here- 
after see that this oily constituent is of much importance also to the prac- 
tical agriculturist. 

§ 26. General differences in composition among the different kinds of 

vegetable food. 

It may be useful shortly to recapitulate the leading differences in 
chemical constitution which exist among the different kinds of vegetable 
food to which I have directed your attention in the present lecture. 

We have seen that each of the varieties of food contains a greater or 
less proportion of three different classes of chemical substances — an 
organic substance containing nitrogen, an organic substance containing 
no nitrogen, and an in-organic substance. But it is interesting to mark 
how in each class of those vegetable products which we gather from the 
earth for our sustenance, the organic substances vary either in composition 
or in chemical characters, while the inorganic matter alters also either in 
kind or quantity. Thus — 

1°. In the seeds of the corn plants — wheat, oats, &c. — the predomi- 
nating ingredient is starch, in connection with a considerable, proportion 
of gluten, and a small quantity of saline matter consisting chiefly of the 
phosphates of potash and of magnesia, and in the case of barley of a 
considerable proportion of lime. 

2°. In the seeds of leguminous plants — the pea, the bean, the vetch, 
&c. — starch is still the predominating ingredient, but it is connected with 
a large quantity of Icgumin, and with a greater proportion of inorganic 
matter — in which phosphate of lime also is more abundant. 

3°. In the oil-bearing seeds — those of hemp, lint, &c. — oil is often the 






630 SPECIAI* DIFFERENCES AMONG SEtDS AND ROOTS. 

predominating ingredient, and it is connected with a large proportion of a 
nitrogenous substance, resembling the curd of milk {casein), and with a 
quantity of ash about equal to that in the pea, but in which the phos- 
phate of lime is said to be still more abundant. 

4°. In the potatoe — starch is the greatly predominating ingredient, but 
it is united with albumen nearly in the same proportion as it is with 
gluten in wheat. The inorganic matter is nearly in the same proportion 
to the dry organic matter, as in the pea and the bean, but is much 
more rich in potash and soda. Still it is more rich in the earthy phos- 
phates than the ash left by wheat and oats, and is inferior in this respect 
only to that of barley. 

5°. In the turnip — sugar and pectin take the place of the starch, and 
the^e are associated with albumen, and with a proportion of inorganic 
matter about equal to that of the potatoe, abounding like it in potash and 
soda, but more rich in the phosphates of lime and of magnesia. 

6°. In the stems of the grasses and clovers — ivoody fibre becomes the 
predominating ingredient, associated apparently with albumen, and with 
a larger proportion of inorganic matter than in any of the other crops. 
In the straws and in some of the grasses which are cut for hay, silica 
forms a large portion of this inorganic matter. In the clovers, lime and 
magnesia take its place. 

The natural differences above described not only exercise an important 
influence upon the mode of culture by which the different crops may be 
most successfully and most abundantly raised, but also upon the way 
in which they can be most skilfully and economically employed in the 
feeding of stock. To this latter point we shall return hereafter. 

§ 27. Average composition and produce of nutritive matter per acre^ by 
each of the usually cultivated crops. 

1°. Average composition. — The relative proportions of the several most 
important constituents contained in our cultivated crops vary, as we have 
seen, with a great number of circumstances. The following table exhi- 
bits the average composition of 1 00 parts of the more common grains, 
roots, and grasses, as nearly as the present state of our knowledge upon 
the subject enables us to represent it. (See table at top of next page.) 

In drawing up this table, I have adopted the proportions of gluten, for 
the most part, from Boussingault. Some of them, however, appear to 
be very doubtful. The proportions of fatty matter are also very uncer- 
tain. With a few exceptions, those above given have been taken from 
Sprengel, and they are, in general, stated considerably too low\ 

It is an interesting fact, that the proportion of fatty matter in and im- 
mediately under the husk of the grains of corn, is generally much greater 
than in the substance of the corn itself. Thus I have found the pollard 
of wheat to jdeld more than twice as much oil as the fine flour obtained 
from the same sample of grain ;* and Dumas states that the husk of oats 
sometimes yields as much as 5 or 6 per cent, of oil. We shall perceive 
the practical value of this fact when we come to consider the use of bran 
and pollard in the fattening of pigs and other kinds of stock. 

' Thus the four portions separated by the miller from a superior sample of wheat grown 
in the neighbourhood of Durham, gave of oil respectively :— fine flour, 1-5 per cent. ; pollard, 
2-4 ; boxings, 3 6 ; and bran, 3-3 per cent. 



AVERAGE COMPOSITION OF THE DIFFERENT CROPS. 



631 





Water. 


Husk or 
woody 
fibre. 


starch, 

gum, and 

sugar. 


Gluten, al- 
bumen, le- 
gumin,&c. 


Fatty 
matter. 


Saline 
matter. 


Wheat . . 


16 


15 


55 


10tol5 


2 to 4 J. 


20 


Barley . . 


15 


15 


60 


121 


2-5 J 


20 


Oats . . . 


16 


20 


50 


14-51 


5-6 J 


3-5 


Rye . . . 


12 


10 


60 


14-5 


30 


10 


Indian corn . 


14 


151 


50 


120 


5 to 9 D. 


1-5 


Buckwheat . 


161 


251 


50 


14-5 


0-41 


1-5 


Beans . . . 


16 


10 


40 


28-0 


2 + 


30 


Peas . . . 


13 


8 


50 


240 


2-81 


2-8 


Potatoes . . 


. ■ 751 


51 


121 


2-25 


0-3 


0-8 to 1 


Turnips . . 


85 


3 


10 


1-2 


1 


0-8 to 1 


Carrots , . 


85 


3 


10 


20 


0-4 


10 


Meadow hay 


14 


30 


40 


71 


2 to 5 D. 


5 to 10 


Clover hay . 


14 


25 


40 


93 


30 


9 


Pea straw 


10tol5 


25 


45 


12-3 


1-5 


5 


Oat do. . . 


12 


45 


35 


1-3 


0-8 


6 


Wheat do. 


12tol5 


50 


30 


1-3 


0-5 


5 


Barley do. 


do. 


50 


30 


1-3 


0-8 


5 


Rye do. . . 


do. 


45 


38 


13 


05 


3 


Indian corn do. 


12 


25 


52 


30 


1-7 


4 



2°. Gross 'produce per acre. — The gross produce, per acre, of the dif- 
ferent crops varies as we have already seen (p. 487) in different districts 
of the country. The weight of each crop in pounds, however, will, in 
general, approach to one or other of the quantities represented by the num- 
bers in the following table : — 













Produce 
per acre. 


Weight 
per bushel. 


Total weight 
in pounds. 


Wheat 25 bush. 60 lbs. 


1500 


—, 










30 






1800 


Barley 










35 

40 




53 lbs. 


1855 
2120 


Oats . . 










40 




42 lbs. 


1680 


_ 










50 






. 2100 


Rye . 










25 




54 lbs. 


1350 


— 










30 






1620 


Indian corn . 








30 




60 lbs. 


1800 


Buckwheat 








30 




46 lbs. 


1380 


Beans 








. 25 




64 lbs. 


1600 


— 








. 30 






1920 


Peas 








. 25 




66 lbs. 


1650 


Weight of produce. 




Weight of produce. 


Potatoes . . .6 tons. 




Carrots . 


. 25 tons. 


— 12 tons. 




Meadow hay 


. 1| tons. 


Turnips . . .20 tons. 
— 30 tons. 




Clover hay 


. 2 tons. 






2 


3 













632 



PRODUCE PER ACRE. 



Wheat straw 
Barley straw 
Oat straw . 



Weight of produce. 
. 3000 lbs. 

3600 " 
. 2100 " 

2500 " 
. 2700 ♦' 

3500 " 



Rye straw 
Bean straw 
Pea straw 



Weight of produce. 

4000 lbs. 

4800 " 
2700 "? 
3200 " 
2700 " ? 



3°. Average produce of nutritive matter per acre. — In the gross pro- 
duce above given, there are contained, according to the first table, the fol- 
lowing average proportions of nutritive matter of various kinds : — 

AVERAGE PRODUCE OF NUTRITIVE MATTER OF DIFFERENT KINDS FROM 
AN ACRE OF THE USUALLY CULTIVATED CROPS. 





Gross produce. 


Husk, or 

woody 

fibre. 

lbs. 


Stanxh, 
sugar, &c. 

lbs. 


Gluten, 
lbs. 


Oil or fat. 
lbs. 


Saline 
matter. 




bush. 


lbs. 


lbs. 


Wheat . 


25 


1,500 


225 


825 


150 to 220 


30 to 60 


30 






30 


1,800 


270 


990 


180 to 260 


36 to 72 


36 


Barley 




35 


1,800 


270 


1080 


216 


45 + 


36 






40 


2,100 


315 


1260 


252 


52 + 


42 


Oats 




40 


1,700 


340 


850 


2301 


95 


60 






50 


2,100 


420 


1050 


290? 


118 


75 


Rye . 




25 


1,300 


130 


780 


190 


40 


13 






30 


1,600 


160 


960 


230 


48 


16 


Indian corr 


I 30 


1,800 


270 


900 


216 


90 to 170 


27 


Buck whea 


t 30 


1,300 


3207 


650 


180 


5 + 


21 


Beans . 


25 


1,600 


160 


640 


450 


32 + 


48 




30 


1,900 


190 


760 


530 


36 + 


57 


Peas 


25 


1,600 


130 


800 


380 


45 


45 


Potatoes 


tons. 
6 


13,500 


675 


1620 


300 


45 


120 




. 12 


27,000 


1350 


3240 


600 


90 


240 


Turnips 


20 


45,000 


1350 


4500 


5401 


1 


400 




. 30 


67,000 


2010 


6700 


800 7 


7 


600 


Carrots 


. 25 


56,000 


1680 


5600 


11207 


200 


560 


Meadow h 


ay IJ 


3,400 


1020 


1360 


240 


70 to 170 


220 


Clover hay 


2 


4,500 


1120 


1800 


420 


135 to 225 


400 


Pea straw 


— 


2,700 


675 


1200 


330 


40 


135 


Wheat stra 


w — 


3,000 


1500 


900 


40 


15 


150 




— 


3,600 


1800 


1080 


48 


18 


180 


Oat straw 


— 


2,700 


1210 


950 


36 


20 


135 




— 


3,500 


1570 


1200 


48 


28 


175 


Barley stra 


w — 


2,100 


1050 


630 


28 


16 


105 




— 


2,500 


1250 


750 


33 


20 


125 


Rye straw 


— 


4,000 


1800 


1500 


53 


20 


120 






— 


4,800 


2200 


1800 


64 


24 


144 



The most uncertain column in this table is that which represents the 
quantity of oil or fat contained in the several kinds of produce. The 
importance ot the whole table to the practical man will appear more 
clearly when we come to treat of the feeding of stock. 



1 



633 



LECTURE XX. 

Of milk and its products.— Properties and composition of the milk of different animals.— 
Circumstances which affect the quality and quantity of milk— species, size, variety, age, 
health, and constitution of the animal, time of milking, kind of food, &c.— Mode of sepa- 
rating and estimating the several constituents of milk.— Sugar of milk, and acid of milk 
(Lactic acid), their composition and properties.— Souring of milk, cause of-^Cream— 
composition and variable proportions of— mode of estimating its quantity— the galactom>>- 
^er.— Churning of milk and cream.— Composition of butter.— Butter-milk.— The solid and 
liquid fats contained in butter— mar^-ann and butter- oil— their separation and properties.— 
Rancidity and preservation of butter.— Composition and properties of the curd (casein).— 
Curdling of milk, natural and artificial— by acids and by animal membranes.— Making and 
action of rennet— howr explained.— Manufacture of cheese.— Varieties of cheese.— Aver- 
age produce of butter and cheese.— Colouring of butter and cheese.— The whey.— Saline 
matter in the whey.— Nature of the saline constituents of milk.— Fermentation of milk.— 
Intoxicating liquor from milk.— Milk vinegar.— Purposes served by milk in the economy 
of nature. 

Of the indirect products of agriculture, milk, and the butter and 
cheese manufactured from it, are among the most important. In our 
large towns these substances may almost be considered as necessaries of 
life, and many extensive agricultural districts are entirely devoted to the 
production of them. The branch of dairy husbandry also presents many 
curious and interesting questions to the scientific enquirer, and upon 
these questions modern chemistry has thrown much light. To the con- 
sideration of this subject, therefore, it is my intention to devote the pre- 
sent lecture. 

§ 1. Of the jjroperties and composition of milk. 
1°. Properties of milk. — The milk of most animals is a white opaque 
liquid, having a slight but peculiar odour — which becomes more distinct 
when the milk is warmed — and an agreeable sweetish taste. It is 
heavier than water — usually in the proportion of about 103 to 100.* 
When newly taken from the animal, cow's milk is alriiost alwa3''s 
slightly alcaline. It speedily loses this character, however, when ex- 
posed to the air, and hence even new milk often exhibits a slight degree 
of acidity. f When left at rest for a number of hours, it separates into 
two portions, throwing up the lighter part to the surface in the form of 
cream. If the whole milk, or the cream alone, be agitated in a proper 
vessel (a churn), the temperature of the liquid undergoes a slight increase, 
it becomes distinctly sour, and the fatty matter separates in the form of 
butter. If a little acid, such as vinegar or diluted muriatic acid, be add- 
ed to milk warmed to about 100° F., it immediately coagulates and se- 
parates into a solid and a liquid part — the curd and the whey. The 
same effect is produced by the addition of rennet or of sour milk — and 
it takes place naturally when milk is left to itself until it becomes sour. 
At a very low temperature, or when kept in a cool place, milk remains 
sweet for a considerable time. At the temperature of 60° F. it soon 

' Or it has a specific gravity of 1020 in woman's milk, to 1041 in sheep's milk ; vvater being 
1000. 

t It is said that if the animal remain long unmilked, the milk will begin to sour in the 
udder, and that hence it is sometime* slightly acid when fresh drawn from the cow. 



534 PROPERTIES AND COMPOSITION OF MILK. 

turns or acquires a sour taste, and at 70° or 80° it sours with still greater 
rapidity. If sour milk be gently warmed it undergoes fermentation, and 
may be made to yield an intoxicating liquor. By longer exposure to the 
air it gradually begins to putrify, becomes disagreeable to the taste, 
emits an unpleasant odour, and ceases to be a wholesome article of 
food. 

The milk of each species of animal is distinguished by some charac- 
ters peculiar to itself. 

Ewe^s milk does not diflfer in appearance from that of the cow, but it 
is generally more dense and thicker, and gives a pale yellow butter, 
which is soft, and soon becomes rancid. The curd is separated from 
this milk with greater difficulty than from that of the cow. 

Goafs milk generally possesses a characteristic unpleasant odour and 
taste, which is said to be less marked in animals of a white colour or 
that are destitute of horns. The butter is always white and hard, and 
keeps long fresh. The milk is considered to be very wholesome, and is 
often recommended to invalids. 

Ass^s milk has much resemblance to that of the woman. It yields 
little cream, and the butter is white and light, and soorr becomes rancid. 
It contains much sugar, and hence soon passes to the state of fermenta- 
tion, -t 

2°. Composition of milk. — Milk, like the numerous vegetable products 
we have had occasion to consider, consists, besides water, of organic sub- 
stances destitute of nitrogen — -sugar and butter; of an organic substance 
containing nitrogen in considerable quantity^ — the curd or casein ; and 
of inorganic or saline matter, partly soluble and partly insoluble in pure 
water. 

The proportions of these several constituents vary in different animals. 
This appears in the following table, which exhibits the composition of 
the milk of several animals in its ordinary state, as found by Henry and 
Chevallier : — 

Woman. 

Casein (cheese) . . 1'52 

Butter 3-55 

Milk sugar . . . 6-50 

Saline matter . . . 0-45 

Water 87-98 



Cow. 


Ass. 


Goat. 


Ewe. 


4-48 


1.82 


4-08 


4-50 


3-13 


0-11 


3-32 


4 20 


4-77 


6-08 


5-23 


5-00 


0-60 


0-34 


0-58 


0-68 


87-02 


91-65 


86-80 


88-62 



100 100 100 100 100 

From the numbers in the above table, it appears that the milk of the 
cow, the goat, and the ewe, contains much more cheesy matter than that 
of the woman or the ass. It is probably this similarity of asses' milk to 
that of the human species, together with its deficiency in butter, which, 
from the most remote times, has recommended it to invalids, as a light 
and easily digested drink. 

§ 2. Of the circumstances by which the composition or quality of the milk 

is modified. 

But the composition or quality of milk varies with a great variety of 
circumstances. Let me direct your attention to a few of these. 

1°. Distance from the time of calving. — The most remarkable depar- 



INFLUENCE OF THE HEALTH OF THE ANIMAL. 535 

ture from the ordinary composition of milk is observed in the heistings, 
colostrum or first milk, yielded by the animal after the birth of its yaung. 
This milk is thicker and yellower than ordinary milk, coagulates by 
heating, and contains an unusually large quantity of casein or cheesy 
matter. Thus the first milk of the cow, the ass, and the goat, consisted, 
in some specimens examined by Henry and Chevallier, of — 

Cow. Ass. Goat. 

Casein . . 15-1 11-6 24-5 

Butter . . 2-6 0-6 5-2 

Milk sugar . — 4-3 3-2 

Mucus . . 2-0 0-7 3-0 

Water . . 80-3 82-8 64-] 



100 100 100 

The increase in the proportion of cheese is peculiarly great in the first 
milk of the ass and the goat. 

This state of tlie milk, however, does not long continue. It gradually 
assumes its ordinary qualities. After ten or twelve days from the time 
of calving, its peculiarities disappear, though in the celebrated dairy dis- 
tricts of Italy it is considered that the milk does not reach perfection until 
about eight months after calving. [Cataneo, 11 latte e i suoi prodotti, p. 
27.] 

2°. Age of the animal. — It is observed that milk of the best quality is 
given only by cows which have been already three or four times in calf. 
Such animals continue to give excellent milk till they are ten or twelve 
years of age, and have had seven or eight calves, when they are 
generally fattened for the butcher. 

3°. Climate and season of the year. — Moist and temperate climates 
are favourable to the production of milk in large quantity. In hot coun- 
tries, and in dry seasons, the quantity is less, but the average quality is 
richer. Cool weather favours the production of cheese and sugar in the 
milk, while hot weather increases the yield of butter, [Sprengel, Che- 
mie fiir Landwirthe, ii., p. 620.] 

In spring the milk is more abundant and of finer flavour. In autumn 
and winter, other things being equal, it yields less cheese, but a larger 
return of butter.* Where cattle are fed upon pasture grass only, this 
observed difference may be derived from a natural difference in the 
qucdity of the herbage upon which the cow is fed. 

4°. Health and general state of the animal. — It is obvious that the 
quality of the milk must be affected by almost every change in the health 
of the animal. It is sensibly less rich in cream also, as soon as the cow 
becomes pregnant, and the same is observed to be the case when it shows 
a tendency to fatten. The poorer the apparent condition of the cow, 
good food bemg given, the richer in general is the milk. 

6°. Tme and frequency of milking. — If the cow be milked only once 
a day, the milk will yield a seventh part more butter than an equal 
quantity of that which is obtained by two milkings in the day. When 
the milk is drawn three times a day, it is more abundant but still less 

' British Husbandry, ii., p. 404. This opinion seems to contradict that of Sprengel in the 
preceding paragraph. Does this difference arise from the locality and other unlike circum- 
stances in which the observations of the two writers were severally made — or are there no 
accurate experiments upon the subject from which a correct result can be drawn ) 



636 INFLUENCE OF THE BREED ON THE QUALITY OF MILK. 

rich. It is also universall}^ remarked, that the morning's milk is of bet- 
ter quality than that obtained in the evening. 

6°T Period at ivhichit is taken, during the milking.'— The milk in the 
udder of the cow is not uniform in quality. That which is first drawn 
off is thin and poor, and gives little cream. That which is last drawn — 
the stroakings, strippings, or afterings — is rich in quality, and yields 
much cream. Compared with the first milk, the same measure of the 
last will give at least eight and often sixteen times as much cream (An- 
derson). The quality of the cream also, and of the milk when skimmed, 
is much better in the later than in the earlier drawn portions of the milk. 

7°. Treatment and, moral state of the animal. — A state of comparadve 
repose is favourable to the performance of all the important functions in 
a healthy animal. Any thing which frets, disturbs, torments, or renders 
it uneasy, affects these functions, and, among other results, lessens the 
quantity or changes the quality of the milk. Such is observed to be the 
case when the cow has been newly deprived of her calf — when she is 
taken from her companions in the pasture field — when her usual place 
in the cow-house is changed — when she is kept long in the house after 
the spring has arrived — when she is hunted in the field or tormented by 
insects — or when any other circumstance occurs by which irritation or 
restlessness is caused, either of a temporary or of a permanent kind. I 
do not enquire at present into the physiological nature of the changes 
which ensue — to the dairy farmer it is of importance chiefly to be familiar 
with the facts. 

8°. The race or breed and size of the animal. — The quality of the milk 
depends much upon the race and size of the cow. As a general 
rule, small races, or small individuals of the larger races, give the richest 
milk from the same kind of food. Thus the small Highland cow gives 
a richer milk than the Ayrshire. The small Alderneys give a richer 
cream than any other breed in common use in this country.* The small 
Kerry cow is said to equal the Alderney in this respect, while the small 
Shetlander has been found in the north of Scotland to give from the same 
food a more profitable return of rich milk than any of the larger races. 
All these breeds are hardy, and will pick up a subsistence from pastures 
on which other breeds would starve. 

The old Yorkshire stock, a cross between the short-horn and the 
Holderness, is preferred by the London cow-keepers as giving the largest 
quantity of milk, though poor in quality. 

The long-horns are preferred in Cheshire and Lancashire because of 
their producing a greater quantity of cheese. The Ayrshire kyloe, on 
ordinary pasture, is said to be unrivalled for abundant produce (Ayton) 
— though the milk is not so rich as that of the small breeds. Various 
crosses have been tried in different parts of the island — and in almost 
every district it has been found that the produce of some particular stock 
is best adapted to the climate, the soil, the natural grasses, the prevailing 
husbandry, or to the kind of dairy produce which it is the interest of the 
farmer to raise in his own peculiar neighbourhood. 

• A very striking illustration of the difference in the quality of the milk of two breeds, in 
the same circumstances, is given by Mr. Malcolm, in his Compendium of Modem Hus- 
bandry. He kept an Alderney and a Suffolk cow, the latter the best he ever saw. During 
seven years, the milk and butter being kept separate, it was found, year after year, that the 
value of the Alderney exceeded that of the Suffolk, though the latter gave more than 
double the quantity of milk at a meal — British Husbandry, ii., p. 397. 



EXPERIMENTS WITH DIFFERENT KINDS OP FOOD. 537 

In the South of Europe, the Swiss breeds are considered the best for 
dairy purposes, and of these that of the Canton of Schweitz, which, in 
size, is intermediate between the large cattle of Fribourg and Berne, and 
the small breed of Hasti. They have enormous udders and give much 
milk, but like that of the Suffolk cows it is less rich in butter and cheese. 

The influence of breed alone upon the quality of the milk is well il- 
lustrated by the result of a series of trials made at Bradley Hall, in 
Derbyshire. During the height of the season, and when fed upon the 
same pasture, cows of four different breeds gave jper day — 

Or 1 lb. of butter was 
Breed. Milk. Butter. yielded by 

Holdemess . . 29 quarts, and 38i oz. 12 quarts of milk. 

Alderney ... 19 '' 2b " 12 ". 

Devon ... 17 " 28 " 9| " 

Ayrshire ... 20 " 34 " 9^ *' 

The Ayrshire cows gave the richest milk and a larger quantity of both 
milk and butter than the Alderneys or Devons, but the Holdemess breed 
surpassed them all. It gave \ lb. more butter than the Ayrshire, and 
nearly one-half more milk. It would appear, therefore, to be admirably 
adapted to the purposes of the town dairyman, whose profit arises from 
milk and cream only. It does not appear what is the relative value of 
this breed in the production of cheese. 

9°. The kind of food. — But the kind of food has probably more in- 
fluence upon the quality of the milk than any other circumstance. It is 
familiar to every dairy farmer that the taste and colour of his milk and 
cream are affected by the plants on which his cows feed, and by the food 
he gives them in the stall. The taste of the wild onion and of the turnip, 
when eaten by the cow, are often perceptible both in the milk and in the 
butter. If madder be given to cows the milk is red, if they eat saffron 
it becomes yellow. It has also been observed from the most remote 
times, that when fed upon one pasture a cow will yield more cheese, 
upon another more butter. From this has arisen the practice more or 
less observed in all dairy districts of varying the food of the cattle — of 
giving some artificial food in addition to that obtained in the natural pas- 
tures — of leaving the animal at liberty to roam over wide pastures and 
thus to seek out for itself, as the sheep does on extensive sheep-walks, 
those different kinds of herbage which are necessary to the production 
of a rich and valuable milk — or in more inclosed districts, and where 
different soils exist on the same farm, of turning them during the former 
part of the day into one field, and during the latter part into another. 

Various sets of experiments have been made with the view of deter- 
mining the relative quantities of butter and cheese produced by the same 
animals, when fed upon different kinds of food. Much, however, re- 
mains yet to be done both by the practical dairy farmer and by the an- 
alytical chemist, before this subject can be fully cleared up. According 
to theory, as I shall more fully explain in my next lecture, the legumi- 
nous plants — clover, tares, &c., and the cultivated seeds of such plants — 
peas and beans, ought to promote the production of cheese ; while oil- 
cake, oats, and other kinds of food which contain much oily matter, 
ought to favour the yield of butter. The most recent experiments we 
possess, however, do not lend any decided confirmation to these theoreti- 



538 EXPERIMENTS WITH DIFFERENT KINDS OF FOOD. 

cal views. The most extensive series of trials lately published is tha 
of Boussingault, [Annales de Chim. et de Phys., Ixxi., p. 79,] from 
which I select the following : — 

FIRST SERIES MADE ON A FRENCH COW. 

Davs after Quarts Composition of the milk per cent. 

ralvinfr Kindoffood. of , ■ » 

^" milk. Casein. Butter. Sugar. Salts. Water. 

200 Hay .... 5 30 45 47 01 87-7 

207 Turnips ... 5i 30 42 50 0-2 87-6 

215 Beet .... 5 34 40 5-3 02 87-1 

229 Potatoes ... 4f 34 40 5-9 02 86-5 

302 Hay and oil-cake 2^ 34 36 60 02 86-8 

SECOND SERIES MADE ON A SWISS COW. 

176 Potatoes and hay 8} 3-3 4-8 5-1 0-3 86-5 

182 Hay and clover 7i 4-0 4-5 4-0 03 87-2 

193 Clover ... 8| 40 22 4-7 0-3 88-8 

204 Do. in flower . 6§ 37 35 52 0-2 87-4 

In the first series of experiments the proportion of cheesy matter and 
of sugar was greatest when beets, potatoes, and oil-cake were given, 
while the largest proportion of butter was obtained from the use of hay 
and the least from oil-cake. 

In the second series the proportion both of cheese and of butter de- 
creased by the use of clover, while the quantity of milk was not per- 
manently increased. 

These two series of experiments may appear to be deserving of less 

reliance because they were not made on successive days, but at varying 

intervals of time. But some recent experiments, made in Lancashire 

by Dr. Playfair, are little more satisfactory. These were made upon a 

short-horned cow, which was fed one day in the field on after-grass, and 

during the four succeeding days in the stall, upon weighed quantities of 

different kinds of food. [Memoirs of the Chemical Society, i., p. 174.] 

Composition of the milk. 

Day's Food. Qts. , ■ ., 

Casein. Butter. Sugar. Salts. Water. 

lo AftPraras., ^ Evening's milk.. 4 5-4 3-7 3-8 0'6 86-5 

1 . Alter grass ^Morning's do.. 4i 3-9 5-6 30 0-5 87-0 

2°. 281bs.Hay P Evening's do.. 3^ 4'9 5'1 38 0-5 85-7 

2|lbs. Oatmeal S Morning's do.. 4 5-4 3-9 4-8 0*5 85-4 

'"•it-'&Jtm^aV-^ Evening's do.. 4 - - - - - 

ilbs.Van?Iour:: ^Morning's do.. 4^ 3-9 46 4-5 0-7 86-3 

^°-^lih=^wLv°^^"" Evening's do.. 5 3-9 6-7 4-6 0-6 84-2 
8 lbs Be^xVlou;-::^ Morning's do.. 4 2-7 4-9 5-0 0-5 86-9 

5°. 141bs.Hay P Evening's do.. 5h 3-9 4-6 3-9 0-5 87-1 

SOlbs. Potatoes... S Morning's do.. 4f 3-5 4-9 3-8 0-5 87*3 

In these experiments there appears an increase in the proportion of but- 
ter and sugar, and in the quantity of milk on the fourth day, when the 
potatoes, hay, and bean flour were given together. On the fifth, when 
potatoes and hay only were given, the quantity of milk went on increas- 
ing, but it was poorer in quality. Could we infer any thing, then, from 
a single day's trial, it would be that the bean meal had aided in the pro- 
duction of butter and sugar — instead of cheese, as theory would indicate 
— while the steamed potatoes had added to the quantity of the milk. 
But no sensible results can justly be expected in regard to the influence 



INFLUENCE OF THE STATE OF PREGNANCY. 639 

of this or that food, except by a much more prolonged series of careful 
observations. 

If we compare the quantity of albumen and casein contained in the 
food, with that yielded in the milk during the four days' experiments of 
Dr. Playfair, we shall find no perceptible relation between the two quan- 
tities. Thus, the cow on the — 

Albumen Of Casein 

2d day eat 2^- lbs., and yielded 0-93 lbs. 

3d " 5 " " 1-0 " 

4th " 4 '* " 0-75 " 

5th " 1-7 " ♦' 0-94 " 

So that, whether, as on the third day double the quantity was eaten, or, 
as on the fifth, little more than half as much as was consumed on the 
second day, the produce of cheesy matter in the milk was sensibly the 
same, on each of the three days. 

We must not, however, from these experiments, infer that the kind of 
food really has no influence upon the quality of the milk — for this con- 
clusion is contradicted by general experience. We must wait rather for 
renewed and more extended practical researches, by which both our 
theory and practice may probably be amended, and by which the con- 
clusions may be reconciled to which they respectively lead us. [See the 
following Lecture " On the feeding of stocAr."] . 

10°. State of pregnancy. — I have already stated (p. 535), that the 
richness in cream diminishes as soon as the cow becomes pregnant. The 
same is no doubt true also of the amount of cheese which the same 
volume of milk will be capable of yielding. It must become poorer in 
every respect, or else considerably less in quantity (p. 541), as soon as the 
cow is with calf, since a portion of the food which might otherwise have 
been einployed in the production of milk, must now be directed to the 
nourishment of the young animal in the womb of the mother. In the 
experiments to which I have just directed your attention in regard to the 
effect of the kind of food upon the quality of the milk, the state of preg- 
nancy of the animal was not taken into consideration, though, as I have 
already said, this must necessarily exercise an important influence upon 
the quality of the milk, whatever be the kind of food upon which the 
animal may have been fed.* To this the want of accordance between 
theory and experiment is probably in part to be ascribed. 

11°. Individual form and constitution of the animal. — But it is well 
known that animals of the same breed, fed on the same food, will yield 
milk not only in different quantities, but also of very different quality. 
In regard to the form, Mr, Youatt states that the " Milch cow should 
have a long thin head, with a brisk but placid eye, — should be thin and 
hollow in the neck, narrow in the breast and point of the shoulder, and 
altogether light in the forequarter — but wide in the loins, with little dew- 
lap, and neither too full fleshed along the chine, nor shewing in any part 
an inclination to put on mucli fat. The udder should especially be 
large, round, and full, with the milk veins protruding, yet thin skinned, 
but not hanging loose or tending far behind. The teats should also stand 
square, all pointing out at equal distances and of the same size, and al- 

* Both of the cows experimented upon by Boussingault were with calf; Dr. Playfair (Joes 
not mention whether his waa so or not. 
23* 



540 EFFECT OF INDIVIDUAL FORM AND CONSTITUTION. 

though neither very large nor thick towards the udder, yet long and 
tapering towards a point. A cow with a large head, a high backbone, a 
small udder and teats, and drawn up in tlie belly, will, beyond all doubt, 
be Ibund a bad milker." [Youatt's Cattle, p. 244, quoted in British Hus- 
bandry, ii., p. 397.] Thus, while much depends upon the breed, the 
form of the individual also has much influence upon its value as a 
milker. 

But independent of form, the quality of the milk is greatly affected by 
the individual constitution of every cow we feed. Thus in a report of 
the produce of butter yielded by each cow of a drove of 22, chiefly of the 
Ayrshire breed — all of which we may presume to have been selected 
for dairy purposes with equal regard to their forms — and which were 
all fed upon the same pastures in Lanarkshire, the yield of milk and 
butter by four of the cows in the same week is given as follows : — 
Milk. Butter. 

A yielded ... 84 quarts, which gave . . . . 3^ lbs. 

F and R each . 86 " " " 5i lbs. 

G yielded ... 88 " " " 7 lbs.* 

Showing that, though the breed, the food, and the yield of milk was 
nearly the same, the cow G produced twice as much butter as the cow 
A — or its milk was twice as rich. This result would have been still 
more interesting had we known the relative quantities of grass consumed 
by these two cows respectively. 

I will not insist upon other causes by which the quality of the milk is 
more or less materially affected. It is said that when stall fed the same 
cow will yield more butter than when pastured in the field — that the age 
of the pasture also influences the yield of butter — and that salt mingled 
with the food improves both the quantity and the quality of the milk. 
There are, probably, few circumstances which are capable in any way 
of affecting the comfort of the animal which will not also modify the 
(juality of the milk it yields. 

§ 3. Of the circumstances which affect the quantity of the milk. 

The epithet good-milker applied to a cow has very different significa- 
tions in different districts and countries. Thus the experiments of 
Bou.ssingault upon the effect of different kinds of food on the quality of 
the milk (p. 538) were made upon a French cow which was considered 
a good milker, and yet when in best condition never gave more than 11 
quarts a day. Two, or even two and a half, times that quantity is not 
considered extraordinary in the height of the season in many parts of our 
island. 

There are three circumstances which principally affect the quantity of 
milk — namely, the breed, the kind of food or pasture, and tlie distance 
from the time of calving. 

1°. The breed. — The smaller breeds of cattle yield, as is to be ex- 
pected, a smaller daily produce of milk — though from the same weight 
of food they occasionally give even a greater volume of milli than the 
larger breeds. 

Good ordinary cows in this country yield, on an average, from 8 to 12 

• Prize Essays of the Higldand Society, New Series, ii., p. 258. 



CIRCUMSTANCES AFFECT THE QUANTITY OF MILK. 541 

quarts a day. The county surveys state the average daily produce of 
dairy cows to be, in — 

Devonshire ... 12 qts. I Lancashire . . . 8 to 9 qts. 

Cheshire .... 8 " | Ayrshire ^ " . 

But the best Ayrshire kyloes will yield an average of 12^ quarts daily, 
during 10 months of the year (Ayton). 
The yearly produce of the best Ayrshire kyloes is stated by Mr. 

Ayton at 4000 qts 

Of average Ayrshire stock 2400 " 

Good short-horns, grazed in summer, and fed on hay and tur- 
nips in winter (Dickson) ....... 4000 '* 

Mixed breeds in Lancashire (Dickson) ..... 3500 " 

Large dairy of mixed long and short-horns, at Workington 

Hall, taking an average of 4 years (Mr. Curwen) . . 3700 *' 
Crossed breeds in many localities are found more productive in milk 
than pure stock of any of the native races of cattle. 

2°. Food and pasture. — In the same animal the quantity of milk is 
known to be greatly influenced by the kind of food. This is best under- 
stood in the neighbourhood of large towns where the profit of the dairy- 
man is dependent upon the quantity* rather than upon the quality of his 
milk. Hence the value of highly succulent foods — of the grass of irri- 
gated meadows — of mashed and steamed food — of brewers' grains — of 
turnips, potatoes and beets — and of other similar vegetable productions 
which contain much water intimately mixed with nutritive matter, and 
thus tend both to aid in the production of milk and to increase its quan- 
tity. 

3°. Distance from the time of calving. — It is a well-known fact that 
cows in general after the first two months from the time of calving, 
though fed upon the same food in equal quantity, begin gradually to give 
less milk, till at the end of about 10 months they become altogether, or 
nearly, dry. In the best Ayrshire k3'^loes, the rate of this decrease is thus 
represented by Mr. Ayton : — 

First fifty days, 24 qts. per day,- 



Second 


do. 


20 


Third 


do. 


14 


Fourth 


do. 


8 


Fifth 


do. 


8 


Sixth 


do. 


6 



day,- 


-or in all, 1200 qts. 




1000 " 




'♦ 700 " 




u 400 " 




u 400 " 




" 300 " 



Some cows indeed do not run dry throughout the whole year, but tliese 
may be considered as exceptions to the general rule. By feeding them 
upon brewer's grains, mashes, and succulent grass, the milk-sellers near 
our large towns occasionally keep the same cow in profitable milking 
condition for three years and upwards. f Such cows are generally fat- 
tened after they have become dry — indeed as they cease to give milk, 
they generally lay on fat in its stead — and, as soon as they are consider- 
ed ripe, are sold off to the butcher. 

* It is quoted, even by forei<;n writers, as a fair joke against the dairy establishments of 
our large towns, that among the advantages possessed by one which was advertised for sale, 
much stress was laid upon a never-failing pump. — See II latte e i suoi produtti. p. 67. 

t Even on shipboard I have heard of a cow being kept in milk during the whole of a three 
years' cruise — the food being principally a kind of pease soup. After the first year, how- 
ever, the milk is said to bpcome thinner and more watery. 



642 MODE OF SEPARATING THE CONSTITUENTS OF MILK. 

§ 4. Of the mode of separating and estimating the several constituents 

of milk. 

1°. If a weighed quantity of milk be allowed to stand for a sufficient 
length of time, the cream will rise to the top, and may be easily skim- 
med off. If this cream be gently heated the butter in an oily form will 
collect upon the surface, and when cold may be separated from the 
water beneath, and its weight determined. 

2°. If the skimmed milk be gently warmed, and a little vinegar or 
rennet then added to it, the curd will separate, and may be collected in a 
cloth, pressed, dried, and weighed. 

.3°. If a second equal portion of the milk be weighed and then evap- 
orated to dryness by a gentle heat and again weighed, the loss will be 
the quantity of water which the milk contained. 

4°. If now the dried milk be burned in the air till all the combustible 
matter disappears, and the residue be weighed, the quantity of inorganic 
saline matter will be determined. 

5°. Supposing those processes to be performed with tolerable accuracy, 
the difference between the sum of the weight of the water, butter, curd, 
and ash, and the weight of the milk employed, will nearly represent 
that of the sugar contained in the given quantity of milk. 

For many purposes a rude examination of milk after this manner may 
be suffi.cient, but where any thing like an accurate analysis is required, 
more refined methods must be adopted. In such cases, the following 
appears to be the best which has hitherto been recommended. [Haid- 
len, Annal. der Chem. & Phar., xlv., p. 263.] 

a. The butter. — The weighed quantity of milk is mixed with one- 
sixth of its weight of common unburnt gypsum previously reduced to a 
very fine powder. The whole is then evaporated to dryness with fre- 
quent stirring at the heat of boiling water (212° F.) A brittle mass is 
obtained, which is reduced to fine powder. By digesting this powder in 
ether, the whole of the butter is dissolved out, and by evaporating the 
ether, may be obtained in a pure state and weighed. Or the powder 
itself, after being treated with ether, may be dried and weighed. The 
butter is then estimated by the loss. 

b. The sugar. — After the removal of the butter, alcohol is poured upon 
the powder and digested with it. This takes up the sugar with a little 
saline matter soluble in alcohol. By evaporating this solution and 
weighing the dry residue, the quantity of sugar is determined. Or, as 
before, the powder itself may be dried and weighed and the sugar esti- 
mated by the loss. If we wish to estimate the small quantity of inor- 
ganic saline matter which has been taken up along with the sugar, it 
may be done by burning the latter in the air, and weighing the residue. 

c. The saline matter. — A second weighed portion of milk is now evap- 
orated carefully to dryness and again weighed. The loss is the water. 
The dried milk is then burned in the air. The weight of the incombus- 
tible ash indicates the proportion of inorganic saline matter contained in 
the milk. 

d. The casein. — The weight of the butter, sugar, saline matter and 
water being thus known and added together, the deficiency is the weight 
of the casein. 



PROPERTIES OF THE SUGAR OF MILK. 543 

§ 5. Of the augar of milk, and of the acid of milk or lactic arid. 

Before I can hope to make you uiulerstand llie nature of the (changes 
which take place during the souring, the churning, and the curdling of 
milk, it will be necessary to make you acquainted with the sugar of 
milk, and with lactic acid or the acid of milk. 

1°. Sugar of milk. — When the curd is separated from milk, the raw 
whey afterwards boiled — with or without the addition of new and butter 
milk — and the floating churd skimmed off or separated by straining 
through a cloth, the whey is obtained nearly free from butter and cheese. 
By mixing it while hot with well beat white of egg, the remainder of the 
curd is coagulated, and may be removed by again straining through 
cloth. If the clear whey, thus obtained, be boiled down in a pan to one 
fourth of its bulk, then poured into an earthen dish, and set aside for a 
few days in a cool place, minute hard white crystals gradually de- 
posit themselves upon the sides and bottom of the vessel. These crystals 
are sugar of milk. A second portion may be obtained by evaporating 
the remaining whey still further, and again setting aside. If the whey 
be at once evaporated to dryness a white mass of impure sugar is pre- 
pared, which in many places is used as an article of food. Of the purer 
variety large quantities are extracted from milk by the Swiss shepherds, 
and in their country it forms an important article of commerce. 

The sugar of milk is less sweet than that of the grape, or of the sugar 
cane. It is harder also, and much less soluble in water, and is gritty 
between the teeth. This sugar undergoes no change when exposed to 
the air, either in the dry state or when dissolved in water. But if a little 
of the curd of milk (casein) be introduced into the solution it gradually be- 
comes sour, lactic acid is formed, and the liquid begins to ferment. Car- 
bonic acid is given off — as is the case during the fermentation of other 
liquids — and alcohol is produced. In milk the two substances are na- 
turally intermixed, and it is the presence of the cheesy matter, as we 
shall hereafter see, which at favourable temperatures always causes milk 
of every kind first to become sour and then to ferment. 

The gluten of wheat and animal membranes of various kinds produce 
a similar effect upon solutions of sugar of milk. A piece of bladder, or 
of the gut or stomach of an animal, immersed into a solution of the sugar, 
changes it by degrees into lactic acid, and upon this influence depends 
the effect of the calf's stomach, in the form of rennet, in the curdling of 
milk. The effect of such membranes is more speedy after they have 
been some time taken from the body of the animal, a fact which also ac- 
cords with the long experience of the dairy districts in the preparation of 
rennet. 

When a little sulphuric or muriatic acid is added to a solution of milk 
sugar, it is slowly converted into grape sugar. This change is hastened 
very much by boiling it with the acid. It is supposed that previous to 
the fermentation of milk the sugar it contains undergoes a similar change 
into the sugar of grapes. 

Milk sugar has not hitherto been formed by art. It exists in the milk 
of all mammiferous animals, and from this source alone have we hith- 
erto been able to obtain it. 

2°. The acid of milk — lactic acid. — When milk is exposed to the air 
for a length of time it acquires a sour taste, which gradually increases in 



544 



THE ACID OF MILK, OR LACTIC ACID. 



intensity till at length the whole begins to ferment. This sour taste is 
owing to the production of a peculiar acid, to which the name of acid 
of milk or lactic acid has been given. The same acid is formed during 
the fermentation of the juices of the beet, and of the turnip, in sour cab- 
bage {sauer Jcraut), and sour malt, in brewers' grains wliich have become 
sour, in the sour vegetable mixtures with which cattle are often fed, in 
the waste liquor of the tanners, in the fermented extract of rice, and in 
large quantity during the fermentation of the gluten in the manufacture 
of starch from wtieaten flour, or of a mixture of oat-meal or bean- 
meal with water, which is allowed to stand and become sour. 

The acid, therefore, differs from the sugar of milk in so far that it can 
readily be formed, and in any quantity, by artificial means. As it is 
not employed for any economical purposes, I shall not trouble you with 
the methods by which this acid is obtained in a state of purity. 

It is rarely found in milk when first drawn from the cow, but it very 
soon begins to be formed in it. It is produced from the sugar, through 
the influence of the cheesy matter of the milk. The pure acid may be 
mixed with cold milk without causing it to curdle, but if the mixture be 
heated, the curd forms and speedily separates. It is for the same reason 
that milk may be distinctly sour to the taste, and yet may not coagulate. 
But if such milk be heated it will curdle immediately. So cream when 
sour may not appear so, till it is poured into hot tea, when it will break 
and leave its cheesy matter floating on the surface. 

§ 6. Of the mutual relations which exist between lactic acid and the cane, 
grape, and milk sugars. 

It is important, and I think it will prove interesting to you, to under- 
stand the beautifully simple relation which exists between the sugar of 
milk and this lactic acid, which plays so important a part in nearly all 
your daily operations. 

Cane sugar, grape sugar, milk sugar, and lactic acid, as they exist in 
solution in water or in milk, may all be represented as compounds of car- 
bon with water— or of carbon with hydrogen and oxygen in the propor- 
tions in which they exist in water. Thus they consist respectively of — 

12' Carbon + 12 Water 

Cane sugar . . . 

Grape sugar . . 

Milk sugar . . . 

Lactic acid . . . 

Acetic acid (vinegar) 

I have added acetic acid to this list, to show you that the lactic acid 
bears a similar relation to the sugars as this acid does. You will recol- 
lect that starch, gum, and woody fibre, have also a similar relation to 
the sugars — and tliat by certain apparently simple transformations these 



12C 


+ 


12H + 


120 


or 


12C + 12HO* 


12C 


+ 


14H + 


140 


or 


12 Carbon + 14 Water 
12C -f 14HO 


24C 


+ 


24H + 


240 


or 


24 Carbon + 24 Water 
24C -f 24HO 


6C 


+ 


6H + 


60 


or 


6 Carbon + 6 Water 
6C + 6HO 


4C 


+ 


3H + 


30 


or 


4 Carbon -f- 3 Water 
4C + 3HO 



' C, H, and O, as in our fortner lectures, representing respectively carbon, hydrogen, and 
oxygen, and HO wRter— a compound of hydrogen with oxygen. 



CHANGE OF MILK SUGAR INTO LACTIC ACID. 545 

several substances are capable of being converted into grape sugar. In 
like manner all these sugars by a similar simple transformation are 
readily converted into one or other of the two acids above named. Starch, 
gurn, and woody fibre in favourable circumstances are transformed intc 
sugar, (see Lecture VI., p. Ill) — the sugars, in favourable circum- 
stances, are further transformed into the lactic or the acetic acids. 

We have seen that animal membranes or the curd of milk have the 
property of changing these sugars into lactic acid. This they do, though 
excluded from the action of the air, and without the escape of any gas. 
The above formulae show with what apparent simplicity this may be 
accomplished. 

In fact, cane sugar, milk sugar, and lactic acid, as above represented, 
consist of the same elements united together in the same proportions. It 
is easy to conceive theretbre in what way the one may be transformed 
into the other. 

1°. Two of lactic acid are represented by 12C + 12H + 120, which 
is the formula for cane sugar. The transforming action of the animal 
membrane, or of the casein in its state of incipient decay, is therefore 
simply to cause the elements of the sugar to assume a new arrangement 
— in which instead of cane sugar they form a substance having the very 
different properties of lactic acid. 

2°. Again, milk sugar is represented by 24C -f 24H + 240, and 4 
of lactic acid are also equal to 24C + 24H -f- 240 ; the change which 
takes place when milk becomes sour, therefore, is easily understood 
Under the influence of the casein the elements of a portion of the milk 
sugar are made to assume a new arrangement, and the sour lactic acid 
is the result. There is no loss of matter, no new elements are called into 
play, nothing is absorbed from the air or given off" into it — but a simple 
transposition of the elements of the sugar takes place, and the new acid 
compound is produced. 

These changes appear very simple, and yet how difficult it is to con- 
ceive by what mysterious influence the mere contact of this decaying 
membrane or of the casein of the milk, can cause the elements of the 
sugar to break up their old connexion, and to arrange themselves anew 
in another prescribed order, so as to form a compound endowed with 
properties so very different as those of lactic acid. It is beautiful to see 
the simple means by which in nature so many important ends are ac- 
complished — to observe how they are all veiled to the uninstructed — and 
how every slight accession to our knowledge opens up new wonders to 
us even in those ordinary operations with which during our whole lives 
we have been most familiar. 

From these intellectual, in addition to other rewards, which constantly 
follow the study of nature, you will with me draw the conclusion — 
which is ever pressing itself upon our attention — that it is the will and 
intention of the Deity, that all his works shall be thoroughly studied and 
investigated. But you will, I think, agree with me in drawing this con- 
clusion, because of the further and higher moral effect also which such 
investigations tend to produce upon the mind. Every fresh discovery, 
as it opens up new fields of knowledge, forces upon us more distinctly the 
sense of our own ignorance. In the case before us we are delighted by 
the apparent simplicity which the several transformations of starch intc 



546 SOURING AND PRESERVING OF MILK. 

sugar, and of the latter into lactic acid, may be brought about, and seem 
almost to understand how it is done, since it can be effected by a simple 
transposition of their elements. But the after-thought occurs — by what 
kind of power is this change effected ? The materials are certainly pre- 
sent, but how are they made to shift their relative positions, and move 
into their new places ? We have conquered one intellectual difficulty 
only to encounter another apparently still harder to overcome. 

It was said first, I believe by Priestley, [Experiments and Obser- 
vations, ii., p. ix., edition 1781,] " that the greater the circle of light, 
the greater is the boundary of darkness by which it is confined." Thus 
they who know the most are the most strongly impressed with the sense 
of their own want of knowledge. What a fine result this is of large 
acquirements ! And how touchingly it was expressed by Sir Isaac New- 
ton, when he likened his great discoveries to the gathering of a few peb- 
bles along the sea-shore — the vast ocean of natural knowledge lying still 
unexplored before him I 

§ 7. Of the souring and 'preserving of milk. 

The natural souring of milk requires now little explanation. It arises 
from the gradual conversion of the sugar into the acid of milk by the 
action of the casein. There are, however, one or two circumstances con- 
nected with it to which it may be proper to advert. 

1°. If milk be kept at a low temperature, it may be preserved for se- 
veral days without becoming sensibly sour. This is effected in Switzer- 
land by immersing the milk vessels in a shallow trough of cool water, 
which, by means of a running stream, can at any time be renewed. In 
such circumstances the action of the cheesy matter in converting the 
sugar into lactic acid is very slow. 

2°. But if the milk be kept at the temperature of 65° or 70° F. it be- 
comes sour with great rapidity, and if afterwards raised to the boiling 
point curdles immediately. An easy way of preserving milk or cream 
sweet for a longer time, or of removing the sourness when it has already 
come on, is to add to it a small quantity of the common soda, pearl ash, 
or magnesia of the shops. Enough is added, when a little of the milk 
poured into boiling water no longer throws up any curd. As the small 
quantity of soda or magnesia thus added is not unwholesome, cream 
may in this way be kept sweet for a considerable time, or may have its 
sweetness restored when it has already become sour. 

3°. I have already observed to you that animal membrane, the curd of 
milk, or any of those substances which possess the power of changing sugar 
into lactic acid, loose that power if the solution in which they are present 
be raised to the boiUng temperature. Hence if milk be introduced into 
bottles, be then well corked, put into a pan with cold water, and gradually 
raised to the boiling point, and after being allowed to cool be taken out 
and set away in a cool place, the milk may be preserved perfectly 
sweet for upwards of half a-year. 

I mentioned also that if the solution containing the sugar and cheesy 
matter be again exposed to the air after boiling, it will gradually resume 
the property of transforming the sugar into lactic acid. Hence, if milk 
be boiled, it is preserved sweet for a longer period of time, but the 
casein gradually resumes its transforming property, and at the end of a 



SEPARATION OF CREAM FROM THE MILK. 547 

few days turns it sour. If, however, the milk be boiled every morning 
or every second morning, the souring property of the casein is at every 
boiling destroyed again, and the milk may thus be kept fresh for two 
months or more. 

4°. Another mode of preserving milk is to evaporate it to dryness by 
a gentle heat, and under constant stirring. By this means a dry mass is 
obtained which may be preserved for a length of time, and which when 
dissolved in water is said to possess all the properties of the most excel- 
lent milk. It is known in Italy by the name of latteina. [II latte e i 
suoi prodotti, p. 19.] 

§ 8. Of the separation and measurement of cream, the galactometer, the 
composition of cream, and the pireparation of cream-cheese. 

1°. Separation of cream. — The fatty part of the milk which exists in 
the cream, and which forms the butter, is merely mixed with and held in 
suspension by the water of which the milk chiefly consists. In the 
udder of the cow it is in some measure separated from, and floats on, the 
surface of the milk, the later drawn portions being always the richest in 
cream. During the milking, the rich and poor portions are usually 
mixed intimately together again, and thus the after- separation is render- 
ed slower, more difficult, and less complete. That this is really so, is 
proved by two facts — first, that if nalk be well shaken or stirred, so 
as to mix its parts intimately together before it is set aside, the cream 
will be considerably longer in rising to the surface — and second, that 
more cream is obtained by keeping the milk in separate portions as it is 
drawn, and setting these aside to throw up their cream in separate ves- 
sels, than when the whole milking is mixed together. When the collec- 
tion of cream, therefore, is the principal object, economy suggests that 
the first, second, third, and last drawn portions of the milk should be 
kept apart from each other. Even in large dairies this could easily be 
effected by having three or four pails, in one of which the first, in 
another the second milk, and so on, might be collected. 

Cream does not readily rise through any considerable depth of milk ; 
it is usual, therefore, to set it aside in broad shallow vessels in which the 
milk stands at a depth of not more than two or three inches. By this 
means the cream can be more effectually separated within a given time. 

But the temperature of the surrounding air materially affects the 
quantity of cream which milk will yield, or the rapidity with which it 
rises to the surface and can be separated. Thus it is said that from the 
same milk an equal quantity of cream may be extracted in a much 
shorter time during warm than during cold weather — that, for example, 
milk may be perfectly creamed in — 

36 hours, when the temperature of the air is 50° F. 
24 " " " " 55° F. 

18 to 20 hours " " " 68° F. 

10 to 12 " " " 77° F. 

— while, at a temperature of 34° to 37° F., milk may be kept for three 
weeks, without throwing up any notable quantity of cream (Sprengel). 

The reason of this is that the fatty matter of the milk becomes partially 
solidified in cold weather, and is thus imable to rise to the surface of the 
milk so readily as it does when in a wann and perfectly fluid state. 



548 COMPOSITION OF CREAM. 

The above remarks apply to milk of ordinary quality and consistency. 
In very thin or poor milk, in which little cheesy matter is contained, the 
cream will rise more quickly. 

2°. Measurement of cream — the galactometer. — The richness of milk 
is very generally estimated by the bulk of cream which rises to its 
surface ia a given time. For the purpose of testing this richness, a 
simple instrument, dignified by the learned name of a galactometer 
(milk-gauge), has been recommiended and may often be useful. It con- 
sists of a narrow cylindrical vessel or long tube of glass, divided or gra- 
duated into 100 equal parts. This vessel is filled up to 100 with the 
milk to be tested, and at the end of 24 or 36 hours, the quantity of cream 
which has risen is estimated by the number of degrees of space which it 
occupies at the top of the milk. If it cover 3 degrees the milk yields 
3 per cent., if 7 degrees 7 per cent, of cream. This instrument, how- 
ever, will give a result which will be generally less than the truth, be- 
cause the cream will always rise slowly through 5 or 6 inches of milk— 
the smallest length which the instrument can conveniently be — and most 
slowly in the richest and thickest milk. Unless considerable care be 
taken, therefore, this milk-gauge may easily lead to erroneous con- 
clusions in regard to the relative degrees of richness of different samples 
of milk. 

3°. Composition of cream. — Cream does not consist wholly of fatty 
matter (butter), but the globules of fat as they rise bring up with them a 
variable proportion of the casein or curd of the rhilk, and also some of the 
milk sugar. It is owing to the presence of sugar that cream is capable 
of becoming sour, while the casein gives it the property of curdling when 
mixed with acid liquids or with acid fruits. 

The proportion of cheesy matter present in cream depends upon the 
richness of the milk and upon the temperature at which the milk is kept 
during the rising of the cream. In cool weather the fatty matter will 
bring up with it a larger quantity of the curd, and form a thicker cream, 
containing a greater proportion of cheesy matter. The composition of 
cream, therefore, is very variable — much more so than that of milk — 
and depends very much upon the mode in which it is collected. 

A specimen of cream, examined by Berzelius, which had a density 
(specific gravity) of 1-0244, consisted of — 

Butter, separated by agitation 4*5 per cent. 

Cheesy matter, separated by coagulating the butter- 
milk 3-5 " 

Whey 92-0 " 

100 
Some of the butter remained, as is usually the case, in the butter- 
milk, and added a little to the weight of the curd which was afterwards 
separated, but the result of this analysis is sufficient to show that cream 
in general contains a very considerable proportion of cheesy matter- 
sometimes almost as much cheese as butter.* 

' The clouted cream of Devonshire and other Western counties, as well as the butter pre- 
pared from it, probably contains an unusually large quantity of cheese. It is prepared by 
straining the warm milk into large shallow pans into which a little water has previously been 

Eut, allowing these to stand from 6 to 12 hours, and then carefully heating them over a slow 
re, or on a hot plate, till the milk approaches the boiling point. The milk, however, must 



i 



CREAM-CHEESE AND MASCARPONI. 549 

I would remark, however, that this cream examined by Berzelius 
must have been of an exceedingly poor quality — little richer, indeed, 
than common milk, since 100 lbs. of it would only have yielded 4^ lbs. 
of butter. Cream of good quality in this country, when skillfully 
churned, will yield about one-fourth of its weight of butter, or one wine 
gallon of cream, weighing 8| lbs., will give nearly 2 lbs of butter.* 

A^ . Cream-cheese. — You will now readily understand the nature of 
what is called cream-cheese — how it differs from ordinary cheese and 
from butter, and why it so soon becomes first sour, and then rancid. 

In preparing this cheese the cream in this country is generally, I be- 
lieve, either tied up in a cloth or put into a shallow cheese vat, and al- 
lowed to curdle and di-ain without any addition. The cheesy matter and 
butter remain thus intimately intermixed, and it is more or less rich, ac- 
cording as the proportion of butter to the cheesy matter in the cream is 
greater or less. This cheese becomes soon rancid and unpleasant to the 
taste, because the moist curd, after a certain length of exposure to the 
air, not onl}^ decomposes and becomes unpleasant of itself, but acquires 
the property of changing the butter also and of imparting to it a dis- 
agreeable taste and smell. 

In Italy, cream-cheeses, called ynascarjioni., are made by heating the 
cream nearly to boiling, and adding a little sour whey as the oily matter 
begins to separate. The whole then coagulates, and the curd is taken 
out and set to drain in shapes. As the sour whey is apt to give this 
cheese an unpleasant flavour or a yellow colour, it is said to be better to 
take 20 grains of Tartaric acid for each quart of cream, to dissolve it in 
a little water, and to add this, instead of the sour whey, to the hot cream. 
The acid runs otF in the whey of the cream, and the cheese is colour- 
less and free from foreign flavour. The 7nascarj)oni^ like the English 
cream-cheeses, are covered with leaves or straw, are littled pressed or 
handled, 'and must be eaten fresh. 

§ 9. Of the separation of butter by churning or otherivise. 

Milk is a kind of natural emulsion in which the fatty matter exists in 
the state of very minute globules, suspended in a solution of casein and 
sugar. Cream is a similar emulsion, differing from milk chiefly in con- 
taining a greater number of oily globules and a much smaller proportion 
of water. In milk and cream these globules appear to be surrounded 
with a thin white shell or covering, probably of casein, by which they 
are prevented from running into one another, and collecting into larger 
oily drops. 

But when cream is heated for a length of time, these globules, by their 
lightness, rise to the surface, press nearer to each other, break through 

not actually boil, nor must the skin of the cream be broken. The dishes are now removed 
into the dairy, and allowed to cool. In summer the cream should be churned on th^i fol- 
lowing day — in winter it may stand over two days. The quantity of cream obtained is said 
to be one-fourth greater by this method, and the milk which is left is proportionably poor. 
When milk on which no cream floats is heated nearly to boiling in the air, a pellicle of 
cheesy matter forms on its surface. Such a pellicle may form in a less degree in the scald- 
ding process of Devonshire, and may thus increase the bulk of the cream. The Corstor- 
phine cream of Mid-Lothian resembles the clouted cream very much, and is made in a very 
similar way. 

' A series of analyses of cream, collected under different circumstances, might throw some 
useful light upon the manufacture and preservation of butter. 



550 OF THE SEPARATION OF BUTTER. 

their coverings, and unite into a film of melted fat. In like manner, 
when milk and cream are strongly agitated by any mechanical means, 
the temperature is found to rise, the coverings of the globules are broken 
or separated, and the fatty matter unites into small grains, and finally 
into lumps, which form our ordinary butter. This union of the globules 
appears to be greatly promoted by the presence of a small quantity of 
acid — since in the }>ractice of churning it never takes place until the 
milk or cream has become somewhat sour. 

These two facts afford an explanation of the various methods which 
are in different places ado})ted for the preparation of butter. 

1°. By healing the cream. — When rich cream is heated nearly to boil- 
ing, and is kept for some time at that temperature, the butter gradually 
rises and collects on the surface in the form of a fluid oil. On cooling, this 
oil becomes solid, and may be readily removed from the water and curd 
beneath. The fatty matter of the milk is thus obtained in a purer foma, 
than when butter is prepared in the usual way. It may, therefore, be 
kept for a longer period without salt and without becoming rancid, but it 
has neither the agreeable flavour nor the consistence of churned butter, 
and is, therefore, scarcely known in our climate as an article of food.* 

The same oily kind of butter may also be obtained by melting the 
churned butter and pouring off" the transparent liquid part which floats 
upon the top. This is the only form in which sweet butter is known in 
many parts of Russia. In warm weather it has the consistence of a 
thick oil, is used instead of oil for many culinary purposes, and is de- 
noted, indeed, by the same Russian word. It may be kept for a consi- 
derable time without salt. 

2°. By churning the cream — a. Sour cream. — Cream for the purpose 
of churning is usually allowed to become sour. It ought to be at least 
one day old, but may with advantage be kept several days in cool 
weather — if it be previously well freed from milk and be frequently 
stirred to keep it from curdling. 

This sour cream is put into the churn and worked in the usual way 
till the butter separates. This is collected into lumps, well beat and 
squeezed free from the milk, and in some dairies is washed with pure 
cold water as long as the water is rendered milky. In other localities 
the butter is not washed, but, after being well beat, is carefully freed 
from the remaining inilk by repeated squeezings and dryings with a clean 
cloth. Both methods, no doubt, have their advantages. In the same 
circumstances the washed butter may be more easily preserved in the 
fresh state, while the unwashed butter will probably possess a higher 
flavour. 

b. Sweet cream. — If sweet cream be put into the churn the butter may 
be obtained, but in most cases it requires more labour and longer time, 
without, in the opinion of good judges, affording in general a finer 
quality of butter. In all cases the cream becomes sour during the agi- 
tation and before the butter begins distinctly to form (see p. 554.) 

c. Clouted cream. — The churning of the clouted cream of this and 
other countries forms an exception to the general rule just stated, that 
more time is required in the churning of sweet creams. Clouted cream 

* It is said, that when melted butter is poured into very cold water, it acquires the consis* 
tency and appearance of common butter. 



CHURNING THE WHOLE MILK. 551 

may be churned in the morning after it is made, that is, within 24 hours 
of the time when the milk was taken from the cow — and from such 
cream it is well known that the butter separates with very great ease. But 
in this case the heating of the cream has already disposed the oily matter 
to cohere, an incipient running together of the globules has probably taken 
place before the cream is removed from the milk, and hence the com- 
parative ease with which the churning is effected. I suppose there is 
something peculiar in butter prepared in this way, as it is known in 
other counties by the name of Bohemian butter. It is said to be very 
agreeable in flavour, but it must contain more cheesy matter than the 
butter from ordinary cream. 

3°. Churning the whole milk. — Butter m very many districts is pre- 
pared from the whole milk. This is a much more laborious method — 
from the difficulty of keeping in motion such large quantities of fluid. 
It has the advantage, however, it is said, of giving a larger quantity of 
butter ; and in the neighbourhood of the towns in Scotland and Ireland 
the ready sale obtained for the butter-milk is another inducement for the 
continuance of the practice. 

At Rennes, in Brittany, the milk of the previous evening is poured 
into the churn along with the warm morning's milk, and the mixture is 
allowed to stand for some hours, when the whole is churned. In this 
way it is said that a larger quantity of butter is obtained, and of a more 
delicate flavour. [II latte e i suoi prodotti, p. 112.] 

In the neighbourhood of Glasgow, according to Mr. Ayton,* the milk 
is allowed to stand 6, 12, or 24 hours in the dairy till the whole has 
cooled, and the cream has risen to the surface. Two or three milkings, 
still sweet, are then poured, together with their cream, into a large ves- 
sel, and are left undisturbed till the whole has become distinctly sour, 
and is completely coagulated. The proper sourness is indicated by the 
formation of a stiff" 6ra^ upon the surface which has become uneven (Bal- 
lantyne). Great care must be taken, however, to keep the brat and 
curd unbroken until the milk is about to be churned, for if any of tlie 
whey be separated the air gains admission to it and to the curd, and 
fermentation is induced. By this fermentation the quality of the butter 
may or may not be affected, but that of the butter-milk is almost sure to 
be injured. 

In Holland the practice is a little different. The cream is not allow- 
ed to rise to the surface at all, but the milk is stirred two or three times a 
day, till it gets sour, and so thick that a wooden spoon will stand in it. 
It is then put into the churn, and the working or the separation of the 
butter is assisted by the addition of a quantity of cold water. 

By churning the sour milk in one or other of these ways, the butter 
IS said to be " rich, sound, and well-flavoured." If it be greater in 
quantity — which appears to be the opinion of those who practise it in 
this country, in Germany, and in Holland — it is, according to Sprengel, 
because the fatty matter carries with it from the milk a larger quantity of 
casein than it does in most cases from the cream alone ( ?). 

§ 10. Of the composition of butter. 
Butter prepared by any of the usual methods contains more or less of 

♦ In his Dairy Httsbundry, a work much praised, and which I regret that I have never seen. 



552 COMPOSITION OK BUTTER* 

all the ingredients which exist in milk. It consists, however, essentially 
of the fat of milk intimately mixed with a more or less considerable 
proportion of casein and water, and with a small quantity of sugar of |{ 
milk. Fresh butter is said to contain about one-sixth of its weight (16 t 
per cent.) of these latter substances, and five-sixths of pure fat (Chev- 
reiil). How much of the 16 per cent, usually consists of cheesy matter i 
has not yet been determined.* | 

It is probable, however, that the proportion of cheesy matter contained 
in butter varies very much. The thickness and richness of the milk — 
the mode of preparing the butter, whether from the whole milk or from 
the cream — the way in which the cream is separated from the milk, 
whether by clouting or otherwise — and the nature of the food and pas- 
ture, must all affect in a very considerable degree the relative pro- 
portions of the fatty and cheesy matters of which our domestic butter 
consists. 

Besides the casein and sugar, butter also usually contains some colour- 
ing substance derived from the plants on which the cow has fed, and 
some aromatic or other similar ingredients to which its peculiar flavour 
is owing, and which are also derived from the food on which the animal 
lives. 

The fat of butter may be readily separated from all these substances, 
and obtained in a nearly pure state. Fresh newly-churned butter is 
melted in a cylindrical jar at a temperature of 140° to 180° F., the 
fluid oil poured off" into water heated to the same temperature, and re- 
peatedly shaken with fresh portions as long as any thing soluble is taken 
up. When left at rest in a warm place, the melted fat rises to the sur- 
face in the form of a nearly colourless transparent oil, which, on cooling, 
hardens into a colourless mass. 

This pure fat may be preserved for a much longer time without be- 
coming rancid (Thenard). It is the various substances with which its 
fatty matter is mixed that give to common butter its tendency to become 
so speedily rancid and to acquire an unpleasant taste. To the nume- 
rous precautions which have bsen adopted with the view of counteract- 
ing this tendency, and of preserving the sweet taste of butter, I shall pre- 
sently direct your attention. 

§ 11. Of the average quantity of butter yielded by milk and cream, and 
of the yearly produce of a cow. 

I have already made you acquainted with some of those numerous 
circumstances by which the quality of milk is affected. These same 
circumstances will necessarily more or less affect the quantity of butter 
also, which a given weight or measure of milk can be made to yield. 

Thus in the King William's town dairy (County Kerry), the average 
quantity of milk and butter yielded by the Kerry and Ayrshire breeds 
respectively was, in a whole year — 

Ayrshire coiv, 1328 quarts, of which 9| to 9^^ quarts gave 1 lb. of but- 
ter. 

* Since the above was written, two samples of fresh butter, from cream, examined in my 
laboratory, have yielded only 0-5 and 07 per cent, respectively of cheesy matter. This Is 
certainly a mucli smaller quantity than 1 had expected. Does butter from the tchole milk 
contain more 1 A aeries of such examiuatimis would prove not tuiLnteresting. 



QUANTITY or BUTTER YIELDED BY MILK. 563 

Kerry cow,, 1264 quarts, of which from 8 quarts to Q\ gave 1 lb. of 
butter. 

Showing, as I have before stated, (p. 536), that the small Kerry cow, 
upon the same pasture, will give a richer milk even than the Ayrshire. 

In Holstein and Lunenburg again, it is considered, on an average, 
that 15 quarts of milk will yield 1 lb. of butter. The milk in that 
country, therefore, must be very much poorer in butter. [Journal of the 
Royal Agricultural Society, I. p. 386.] 

The result of numerous trials, however, made upon the milk and 
cream of cows considered as good butter-givers, in this country, has 
established the following average relation between milk, cream, and but- 
ter : — 

Milk. Cream. Butter. 

18 to 21 lbs. I . , , W lbs. ? , ,, 

9tollqts.J y^^^^ j2qts.M ""' ^ ^^' 

The cow, therefore, that yields 3000 quarts of milk should produce, 
where butter is the principal object of the farmer, about 300 lbs. of but- 
ter, or 1 lb. a day for 300 days in the year. 

This is not a large daily produce, since some cows have been known 
to give for a limited time as much as two or even three pounds of butter 
in a single day. It is a large quantity however, taken as the average of 
a lengthened period of time, and hence such cases as that of Mr. Cramp's 
cow, which for four years continuously yielded nearly a pound aud a 
half of butterf every day, are naturally quoted as extraordinary. 

In most districts the average of the whole year is much less than a 
pound a day, even for ten months only. In Devon, for the first twenty 
weeks after calving, a good cow will yield 12 quarts of milk a day, from 
which, by the method of scalding, a pound and a quarter of butter can be 
extracted. 

In South Holland, [Loudon's Encyclopaedia,] a good cow will pro- 
duce during the summer months about 76 lbs. of butter. In the high 
pastures of Scaria in Switzerland, a cow will yield during the ninety 
days of summer about 40 lbs. of butter, or less than half a pound a day. 
In Holstein and Lunenburg it is considered a fair return if a cow yields 
100 lbs. of butter, and even in England, [British Husbandry, II., p. 
404,] 160 to 180 lbs. is reckoned a fair annual produce for a cow, or from 
8 to 9 ounces a day for ten months in the year. 

§ 12. Of the circumstances which affect the quality of butter. 
It is known that the butter produced in one district of the country, dif- 
fers often in quality from that produced in another, even though the same 
method of manufacture be adopted. In different seasons also the same 
farm will produce different qualities of butter — thus it is said that cows 
which are pastured yield the most pleasant butter in May, when the first 
green fodder comes in — that the finest flavoured is given by cows fed upon 
spurrey (Sprengel) — that it is generally the hardest when the animal 
lives upon dry food — and that autumn butter is best for long keeping. 

* The quarts spoken of in this lecture are old wine quarts, of which 5 make an imperial 
gallon. A wine gallon of milk or cream weighs about 8 lbs. 4 oz., an imperial gallon about 
10 lbs. 5 oz. About two imperial gallons, therefore, should yield a pound of butter. 

t It gave in four years 2132 lbs. of butter from 23,559 quarts of milk, or 16 qudrta a day, of 
which U quarts gave a pound of butter. 



554 FIRST AND SECOND MILK AND CREAM. 

These differences may all be ascribed to varieties or natural differences 
in the pasture or fodder upon which the cow is fed.* The constitution of 
the aaimal also is known to affect the quality of the butter — since there 
are some animals which with the best food will never give first-rate but- 
ter. 

In all such cases as these, however, the quality of the butter is almost 
entirely dependent upon that of the milk ^oni which it is made, so that 
whatever affects the quality of the milk must influence also that of the 
butter prepared from it. But as I have already considered the circum- 
stances by which the quality of the milk is principally modified (p. 
534), I shall not farther advert to this subject at present. 

But from the same milk, and even from the same cream, by different 
modes of procedure, very different qualities of butter may be obtained. 
The mode of making or extracting butter, therefore, is highly worthy of 
3' )ur attention. Let us consider a few of the more important circum- 
stances under which different qualities of butter may be extracted from 
the same quality of milk or cream. 

1°. First and second drawn milk. — If the milk be collected in two or 
three successive portions, as it comes from the cow, we have already 
seen (p. 536), that the last drawn portion wall be much richer than that 
which has been taken first. The cream yielded by it will also be richer, 
and of a finer and higher flavour. Whether, therefore, the butter be ex- 
tracted directly from the whole milk, or from the cream, the butter ob- 
tained from the three successive portions will differ in quality almost as 
much as the several portions of milk themselves. 

A practical application of this fact is made in some of the Highland 
counties of Scotland, and in other districts, where the calves are allowed 
to suck, or are fed with, the first half of the milk as it comes from the 
cow — the latter and richest half only being reserved for dairy purposes. 
This second milk is found to afford an exquisite butter. 

2°. First and second cream. — In like manner the first cream that rises j 
upon any milk is always the richest, and gives the finest flavoured but- ' 
ter. The after-creamings are not only poorer in butter, but yield it of a 
whiter colour and of inferior quality. 

This fact again is well understood, and has been long practically ap- 
plied in the neighbourhood of Epping, which is celebrated for the excel- 
lence of its butter. The cream of the first 24 hours is set aside and 
churned by itself. The second and third creams produce a pale, less 
pleasant butter, which always sells for an inferior price. Any admix- 
ture of the after-creamings causes a corresponding diminution in the value 1 1 
of the butter produced. To produce the most exquisite butter the cream *' 
of the first eight hours only ought to be taken. 

3°. Mode of creaming. — The rapidity with which cream rises to the 
surface, either naturally or when influenced by art, affects the quality of 
the cream, and consequently that of the butter made from it. In warm 
weather it rises more quickly than in cold, and more quickly still when 
the milk is heated, as in the preparation of clouted cream. The butter 

* The influence of the food given in the stall and of the plants eaten in the pasture, upon 
the colour and flavour of the butler, is familiar to all practical men. The turnipy taste of 
the butter in wrinter — the garlic taste in summer, where the wild onion grows in the pastures 
— and the alleged effect of raw potatoes in winter, in giving a rich colour to the butter, jure 
eommon examples of this kind. 



TOO RAPID OR OVER-CHURNING. 565 

(Bohemian butter) obtained from such cream — from cream thus rapidly 
brought to the surface — may be expected to differ both in flavour, in con- 
sistency, and in composition, from that yielded by the cream of the same 
milk when allowed to rise in the usual manner. 

4°. Sourness of the cream. — For the production of the best butter it is 
necessary that the cream should be sufficiently sour before it is put into 
the churn. Butter made from sweet cream (not clouted), is neither good 
in quality nor large in quantity, and longer time is required in churning. 
It is an unprofitable method (Ballantyne). 

5°. Quickness in churning. — The more quickly milk or cream is 
churned, the paler, the softer, and the less rich the butter. Cream, ac- 
cording to Mr. Ayton, may be safely churned in an hour and a half, 
while milk ought to obtain from two to three hours. The churning 
ought also to be regular, slower in warm weather that the butter may 
not be soft and white, and quicker in winter that the proper temperature 
may be kept up. 

Mr. Blacker has lately introduced into this country a barrel-churn in- 
vented by a Mr. Valcourt, which, being placed in a trough of water of 
the proper temperature, readily imparts the degree of heat required by 
the milk or cream without the necessity of adding warm water to the 
milk, and churns the whole in ten or twelve minutes. It is said also to 
give a larger weight of butter from the same quantity of milk. If the 
quality be really as good by this quick churning, the alleged inferiority 
in the quality of butter churned quickly in the common churn can not 
be due to the mere rapidity of churning alone. 

6°. Over- churning. — When the process of churning is continued after 
the full separation of the butter, it loses its fine yellowish, waxy ap- 
pearance, and becomes soft and light coloured. The weight of the butter, 
however, is said to be considerably increased ; and hence that in Lan- 
cashire over-churning is frequently practised in the* manufacture of fresh 
butter for immediate sale (Dr. Traill.) 

7°. Temperature of the milk or cream. — Much also depends upon the 
temperature of the milk or cream when the churning is commenced. 
Cream when put into the churn should never be warmer than 53° to 55° 
F. It rises during the churning from 4° to 10° F. above its original 
temperature. When the whole milk is churned, tne temperature should 
be raised to 65° F., which is best done by pouring in hot water into the 
churn while the milk is kept in motion.* 

The importance of attending to the temperature and to the quickness 
of churning, when the best quality of butter is required, is shown by the 
two following series of results obtained in the churning of cream at dif- 
ferent temperatures and with different degrees of rapidity. 

The first series was obtained in the August and September of 1823, by 
Dr. Barclay and Mr. Allan. The quantity of cream churned in each 
experiment was 15 wine gallons, weighing from 8 lbs. to S\ lbs. per gal- 
lon. 

• Ballantyne, Transactions of the Highland Society, New Series, I., p. 24. Some object to 
this method of adding hot water, saying that it renders the butter pale and less valuable m the 
market. This is by no means universally the case, and the keeping the milk in motion, 
while the water is added, may possibly, in some cases, make the difference. lu other cases, 
may be owing to natural differences in the quality of the milks operated upon. 

24 



556 TEMPERATURE OF THE MILK OR CREAM. 

Temperature. Quantity of 

,- ■ , Time in Butter 

No. Begin- w„^ Churning, per gallon. (duality of the Butter, 

ning. ^^^- Hours. lb. oz. 

1 50° 60° 4 1 15i Very best, rich, firm, well tasted. 

2 55° 65° '6\ 1 \b\ Not sensibly superior to the former. 

3 58° 67° 3 1 14 Good, but softer. 

4 60° 68° 3 1 12| Soft and spongy. 

5 66° 75° 2| 1 10§ Inferior in every respect. 

The results of these experiments prescribe the temperature of 50 to 55° 
F. for the cream when put into the chum, and from 3| to 4 hours as the 
most eligible for producing butter, both in the largest quantity and of the 
finest quality. Something, however, appears to depend upon the quality 
of the cream ; since the indications of the next series of experiments dif- 
fer considerably from the above, in so far at least as regards the length 
of time expended in churning. 

The following experiments were made in Edinburgh, by Mr. Ballan 
tyne, between June and August, 1825. The quantity of cream he used 
at each churning was 8 wine gallons — weighing 8 lbs. to the gallon, ex- 
tcept hat of the fourth experiment, which weighed 4 ounces le.ss. 

Temperature. Time in Quantity of 
Churn- Butter 



No. Of the When but- ing. per gallon. Quality of the butter, 

cream, ter came. Hours. lbs. oz. 

1 56°F. 60°F. \h 2 1 Inferior; white and softer than No. 2. 

2 52° 56° 2 2 0) The flavour and quality of these two 

3 52° 56 2 2 0) butters could not be surpassed. 

4 65° 67° h 1 15 Soft, white, and milky. 

5 50** 53j° 3 1 15| Good — evidently injured by long churn- 

ing. 

6 53^° 57i° l\ 2 Of Most excellent. High in flavour and 

colour, and solid as wax. 

To obtain butter from cream, therefore, both finest in quality and 
largest in quantity, these two series of experiments prescribe the follow- 
ing temperatures of the cream, and times in the churning — 

Temperature. Time. 

First ... 50° to 55° 3^ to 4 hours 

Second . . 53|° 1\ to 1^ " 

In the temperature both agree. It is probable that the nature of the 
cream obtained at different seasons or in different localities may render 
a longer time necessary in the churning on some occasions or in some 
places than in others. It is certain that the sourer the cream, the sooner 
generally will the butter come.* 

8°. Churning the entire milk. — It is in connection witli the tempera- 
ture at which milk and cream ma}^ respectively be best and most eco- 
nomically churned, that the chances of obtaining a butter of good quality 
at every season of the year appear to be greater when the whole milk is 
used, than when the cream only is put into the churn. 

Cream, when the churning commences, should not be warmer than 
55° F. — milk ought to be raised to 65° F. In winter, either of these tem- 
peratures may be easily attained. In cold weather it is often necessary 

* In sweet cream, when the butter is long in coming, the addition of a little vinegar, brandy, 
or whiskey, will hasten the churning. 



ADVANTAGE OF CHURNING THE WHOLE MILK. 557 

10 add hot water to the cream to raise it even to 55°. But in summer, 
and Pispecially in hot weather, it is difficult, even in cool and well or- 
dered dairies, to keep the cream down to this comparatively low temper- 
ature. Hence if the cream be then churned, a second rate butter, at best, 
is all that can be obtained. 

Milk, on the other hand, requires a temperature of 65° — ten degrees 
liigher than cream — and therefore neither summer nor -udnter weather 
materially affects the ease of churning it. In winter, its temperature is 
raised by hot water, as that of cream is, and even in summer there can 
be few days in our climate — where the milk is kept in a well contrived 
dairy — in which it will not be necessary to add more or less hot water in 
order to raise the milk to 65° F. Thus, where the entire milk is churned, 
the same regular method or system of churning can be carried on through- 
out the whole year. No difficulty is to be apprehended from the state 
of the weather, nor, so long as the quality of the milk remains the same, 
is there reason to apprehend any change in the quality of the butter. 
The winter butter and the summer butter may be alike firm, finely fla 
voured, and rich in colour. 

The alleged advantages of churning the entire milk rather than the 
cream may be thus stated : — 

a. The proper temperature can be readily obtained both in winter and 
in summer. 

b. A hundred gallons of entire milk will give in summer five per cent, 
more butter than ihe cream from the same quantity of milk will give 
(Ballantyne). 

c. Butter of the best quality can be obtained without difficulty both 
in winter and in summer. 

d. No special attention to circumstances or change of method is at 
any time required. The churning in winter and summer is alike simple 
and easy. 

e. The butter is not only of the best quality while fresh, but is also 
best for long keeping, when properly cured or salted (Ballantyne). 

To these advantages it is set oflT, that except in the neighbourhood of 
large towns, the butter-milk is of little value — while from the skimmed- 
milk, a marketable cheese can always be manufactured. But this ought 
to be no objection, where churning the whole milk would otherwise be 
preferred, since it is little more difficult to make cheese from the sour 
butter-milk than from the sweet skimmed-milk. To this point I shall 
direct your attention hereafter. 

9°. Cleanliness. — It seems almost unnecessary for me to allude to 
cleanliness as peculiarly necessary to the manufacture of good butter. 
But I do so to bring under your notice the fact, that cream is remarkable 
for the rapidity witli which it absorbs and becomes tainted by any un- 
pleasant odours. It is very necessary thai the air of the dairy should be 
sweet, that it should be often renewed, and that it should be open in no 
direction from which bad odours can come. 

§ 13. Of the fatty substances ofivhich butter consists, and of the acid of 
butter (butyric acid,) and the capric and caproic acids. 
1°. Butter-fat. — I have already mentioned to you that if the butter as 
it is taken from the churn be melted in water of a temperature not ex- 



638 THE FATTY SUBSTANCES IN BDTTER. 

ceeding 180° F., and be then washed with repealed portions of warm 
water, a nearly colourless fluid oil is obtained, which, if not transpar- 
ent, becomes so when filtered through paper, and when cool congeals into 
a more or less pure white solid fat. If this fat be put into a linen cloth 
and be submitted to a strong pressure in a hydraulic or other press at the 
temperature of 60° F., a slightly yellow, transparent oil will flow out, 
and a solid white fat will remain behind in the linen cloth. The solid 
fat is known to chemists by the name o? margarine. The liquid oil is 
peculiar to butter, at least it has not hitherto been found in any other sub- 
stance ; it is therefore called the oleine of butter, or simply butter-oil. 

The pure fat of butter consists almost entirely of these two substances, 
there being generally present in it only a small quantity of certain fatty 
acids, which I shall presently introduce to your notice. Thus a speci- 
men of butter made in the month of May gave a fat which was found 
by Bromeis to consist of about^ 

Margarine . 68 per cent. 

Butter oil 30 " 

Butyric, caproic, and capric acids .... 2 " 



100* 
But the proportion of the solid and fluid fats in butter varies very much. 
It is familiar in every dairy that the butter is harder and firmer at 
one time and with one mode of churning than with another, — and this 
greater firmness depends mainly upon the presence of the solid fat {mar- 
garine) in larger proportion. According to Braconnot, summer butter 
contains much more of the hutter-oil than winter butter does ; and he 
states their relative proportions in these two seasons, in the butter of the 
Vosges, which he examined, to be as follows : — 

Summer. Winter. 

Margarine 40 65 

Butter oil 60 35 



100 100 

Of course these proportions are not to be considered as constant. In- 
deed, the proportion of oil here given for summer butter is much greater 
than in the butter examined by Bromeis. It is probable, therefore, that 
the relative proportions of the two fats are affected by climate, by sea- 
son, by the race, the food, and the constitution of the animal; by the way 
in which the butter is made, by the manner in which it is kept, and by 
other circiunstances not hitherto investigated. 

2°. Margarine. — This solid fat, which exists so largely in butter, is 
also the solid ingredient in olive oil, and in goose and human fat. But- 
ter, therefore, appears to be a most natural food for the human race, since 
it contains so large a proportion of one of those substances which enter 
directly into the constitution of the human frame. 

Margarine is white, hard, and brittle, and melts at 118° F. In the 
pure state it may be kept for a Jength of time without undergoing any 
sensible change, but in the state of mixture in which it exists in milk and 
butter it is apt to absorb oxygen from the atmosphere, and to be partially 

* Annal. der Chem. und Phar.f xUi., p. 70. 



PROPERTIES OF THE SUGAR OP MILK. 559 

changed into butter oil, and into one or other of those fatty acids which 
are present in butter in smaller quantity. 

3°. Margaric acid. — When this fat (Margarine) is introduced into a 
hot solution of caustic potash, it readily dissolves and forms a soap. If 
the solution of this soap in water be decomposed by the addition of diluted 
sulphuric acid a white fatty substance separates, which, after being col- 
lected, dried, and dissolved in hot alcohol, crystallizes as the solution 
cools, in the form of pearly scales. This substance is known by the 
name of the margaric (or pearly) acid. Margarine consists of this acid 
in combination with a sweet substance known by the name of glycerine, 
or oil sugar.* 

Margaric acid is represented by the formula 34 C + 34 H + 4 O, or 
C34 H34 O4. To this formula it will be necessary in a few minutes to 
revert. 

Butter oil. — The liquid fat expressed from butter has the appearance 
of an oil, sometimes colourless, but often tinged of a yellow colour. It 
has the taste and smell of butter — mixes readily with alcohol, and be- 
comes solid when cooled down to 32° F. — the freezing point of water. 
It dissolves without difficulty in a solution of caustic potash, and forms 
a soap. 

Acid of huiter-oil — oleic acid of butter. — When the solution of the oil 
in caustic potash is diluted with much water, and decomposed by the ad- 
dition of diluted sulphuric acid, an oily substance is separated, which is 
different from the original oil of butter, possesses acid properties, and is 
known by the name of the oleic acid of butter. This fatty acid has 
never hitherto been obtained from any other substance than the oil of 
butter, and the oil consists of the acid in combination with oil-sugar. 
You will recollect that margarine consists of margaric acid in combination 
with the same sugar (p. 558.) 

* Such is the apparent composition of the two fatty substances, margarine and butter-oil, 
inasmuch as when they are dissolved in a solution of caustic potash, and their solutions 
afterwcirds decomposed by an acid, they are resolved respectively — 
Margarine — into margaric acid and oil-sugar ; 
Butler-oil— inio butter oleic acid and oil-sugar. 

But, for the benefit of my chemical readers (my other readers will please to pass over 
this note), it is necessary to state — 

1°. That a compound is supposed to exist, consisting of 3 atoms of carbon united to 2 of 
hydrogen— C3 H-j, to which the name of lipyle is given. 

2°. That this radical C3 H2 unites with an atom of oxygen, forming C3 H2 O, or oxide of 
lipyle. , 

30. That in neutral fatty bodies, such as margarine^ this oxide exists m combmation 
with a fatty acid. Thus, for example, that— 

,, . . ^ ^Sl of margaric acid = C34 H34 O4 

Margarine consists of j^ ^j- ^^^^ ^f u^yjg = C3 H2 O 

Forming, together, 1 of margarine =C37H36 05 

And r „ •; ^f S 1 of oleic acid of butter = C34 Hal O5 

butter.otl of J J ^f ^^j^je ^f Upyle = C3 H2 O 

Forming, together, 1 of butter-oil =:C37H33 06 

40. And that when this oxide of lipyle is separated from its combination with the fatty 
acids it unites with a quantity of water, and forms glycerine or oil-sugar. Thus— 

2 of oxide of lipyle = C6 H4 O2 united to 

3 of water = H3 O3 give 

1 of glycerine (oil-sugar) . . • . . . . = Ce H? O5 
50 The above 's the view of Berzelius, but Redtenbacher has recently suggested, [Annal. 
der Chem. und Phar, XLVII., p. 141,] that a known substance called acrolein exists in the 



560 CHANGE OF MARGARINE INTO OLEIC ACID. 

When pure, this oily acid is colourless and transparent, and is re- 
markable for ike rapidity with which it absorbs oxygen from the atmos- 
phere, and becomes converted into new chemical compounds. It is re- 
presented by the formula 34C + 31H + 50, or C34 H31 O5. 
Let us compare this formula with that of the margaric acid : 

Margaric acid = C34 H34 O4 

Butter oleic acid . . . . = C34 H31 O5 



Difference . . . . . . +H3 — Oi 

or, if 3 of hydrogen be taken from the margaric acid and 1 of oxygen 
added to it, it will be converted into the oleic acid. 

Now this may be effected by simply supposing one atom of margaric 
acid to absorb four atoms of oxygen from the atmosphere. Thus — 

1 of margaric acid = C34 H34 O4 

4 of oxygen . . := O4 

1 of oleic acid + ^ of water. 

C34 H34 Os , or C34 H31 O5 + 3HO. 

So that either in the body of the animal, in the milk while it remaijis 
in the udder, or when it is exposed to the air after being drawn from the 
cow, or even in the churn itself, it may happen that a portion of the 
margaric acid may absorb oxygen and become changed into the oleic 
acid. It may also be that this change, this absorption of oxygen, is pro- 
moted by warm and retarded by cold weather, and that thus the butter 
is rendered generally softer in the summer and harder in the winter sea- 
son. But these are as yet only conjectures ; for, after all, the relative pro- 
portions of the soft and hard fat in butter at different times of the year 
may depend upon natural differences in the herbage at the several 
seasons, or upon some other causes which have not as yet been in- 
vestigated. 

5°. Butyric, capric, and caproic acids. — These substances, as I have 
already stated to you, exist in butter only in small quantity — to the 
amount of 2 or 3 per cent. To these acids, and especially to the capric 
and caproic, butter owes its disagreeable smell when it becomes rancid. 
They do not exist, naturally, to any unpleasant extent in perfectly fresh 
butter — they are gradually formed in it, however, when fresh butter 
is exposed to the air. I do not enter into any detail of their proper- 
ties, or of the mode of extracting them from butter, because these points 

fats in combination with the fatty acid. Tiiis acrolein is represented by C6 H4 O2, which 
is exactly the constitution of 2 of lipyle. So that according to this view the soUd fat of but- 
ter would consist of— 

2 of margaric acid . . . . = C68 H68 08 

1 of acrolein = C6 H4 O2 

2 of margaric acid . . . . = C74 H72 Oio 

and, by a like substitution of acrolein for oxide of lipyle, may the constitution of butter-oil 
be represented. 

The principal known fact in favour of this view of Redtenbacher is, that when glycerine is 
distilled with anhydrous phosphoric acid, acrolein is produced. He supposes that the acid 
takes the elements of 3 atoms of water from glycerine, forming acrolein : since if from — 

1 of glycerine = Ce H7 Os we take 

3 of water = H3 Od 

Acrolein remains = Ce H4 O2 

The conversion of acrolein into glycerine, when it is separated from the fatty acids, is sup- 
posed to proceed, as in the case of lipyle, from its combination with the water at the moment 
of extrication. Further researches are yet required to clear up this subject. 



PROPERTIES OF THE CURD OF MILK. 561 

are of less interest or importance to you. It is necessary only, to a 
clear understanding of the kind of changes which take place when butter 
becomes rancid, that I should exhibit to you the formulae by which these 
acid bodies are severally represented : — 

Butyric acid = Cs Ug O4 

Caproic acid = C12 H9 O3 

Capric acid = Cis H14 O3 
We shall see how these substances are produced from the solid and 
fluid fats of butter, when we come to treat of the preservation of butter. 

§ 14. Of casein or the curd of milk and its properties. 

The casein or cheesy matter of milk may be obtained nearly pure by 
the following process : — Heat a quantity of milk which has stood for 5 
or 6 hours, as if you intended to prepare clouted cream (p. 548), let it 
cool, and separate the cream completely. Add now to the milk a little 
vinegar and heat it gently. The whole will coagulate, and the curd will 
separate. Pour off the whey, and wash the curd well by kneading it 
with repeated portions of water. When pressed and dried, this will be 
casein sufficiently pure for ordinary purposes. It may be made still 
more pure by dissolving it in a weak solution of carbonate of soda, al- 
lowing the solution to stand for 12 hours in a shallow vessel, separating 
any cream that may rise to the surface, again throwing down the curd 
by vinegar, washing it frequently, and occasionally boiling it with pure 
water. By repeating this process two or three times, it may be obtained 
almost entirely free from the fatty and saline matters of the milk. 

Casein thus prepared reddens vegetable blues, and is therefore a 
slightly acid substance. It is very sparingly soluble in water — 400 lbs. 
of cold water dissolving only 1 lb. of pure casein (Rochleder). It dis- 
solves readily, however, and in large quantity, in a weak solution of the 
carbonate of potash or of soda, and to some extent even in lime-water. 
These solutions are coagulated by the addition of an acid — of sulphuric 
acid, of vinegar, or of lactic acid — and the curd readily separates on the 
application of a gentle heat. If a large quantity of acid be added, a por- 
tion of the casein is re-dissolved. This property of dissolving in weak 
alcaline (potash or soda) solutions, satisfactorily explains what takes 
place during the curdling of milk, as we shall hereafter see (p. 667). 

The casein of milk is identical in chemical constitution with the fibnn 
of wheat, the legumin of the pea and bean,* and the albumen of the 
egg or of vegetable substances. Hence the opinion has naturally arisen 
among chemists, that the cheesy matter contained in an animal's milk is 
derived directly, and without change, from the food on which it lives. 
The probability of this opinion will come naturally under our considera- 
tion in the following lecture. (See next lecture, " On the feeding of 
stock.'') 

Casein possesses still one property more remarkable than any of its 

' In page 394 it is stated, on the authority of Dumas, that the legumin of the pea and bean 
differs in composition from fibrin and alhunven. Since that sheet was published, it appears, 
from the experiments of Rochleder (Annal. der Chem. und Pharm., xlvi., p. 162), that the 
legumin which Dumas extracted from the almond, analysed, and supposed to be identical 
with the legumin of the bean and pea, is not so, but is in reality a different substance ; and 
that the legumin of peas does agree in composition with the casein of milk. 



562 ACTION OF CASEIN UPON SUGAR. 

Others, and exceedingly interesting to the practical agriculturist. Let 
me explain this property a little more in detail. 

§ 15. Of the relations of casein to the sugars and the fats. 
1°. Relation to the sugars. — a. Production of lactic acid. — I have 
already adverted (p. 543) to the remarkable property which casein tdos- 
sesses of gradually converting milk or other sugars into lactic acid.^ If 
a small quantity of this substance, either in the state of fresh curd or in 
the purer form just described, be introduced into a solution of cane-sugar, 
or of sugar of milk, lactic acid begins very soon to be formed. Thus 
the casein it contains is the cause of the souring of milk. In like man- 
ner it is the casein contained in bean or pea-meal which makes it so 
soon become sour when mixed with water. 

h. Production of butyric acid. — But the transforming action of casein 
doos not end when this change is produced. After a longer time a 
further alteration is effected by its means. A fermentation commences, 
during which carbonic acid and pure hydrogen gases are given off, and 
butyric acid is produced (Pelouze and Gelis). Let us consider the 
nature of this new change. 

Butyric acid is represented by Cs Hs O4 ; and lactic acid, as we have 
seen, by Ce He Oe ; therefore — 

4 of lacticacid = C24 H24 O24 and 

3 of butyric acid = C24 H24 O12 

Difference ..... O12 
That is to say, that 4 of lactic acid, in order to be converted into 3 of 
butyric acid, must give off 12 of oxygen. But during the fermentation 
which accompanies the change no oxygen is given off. The gases 
which escape are carbonic acid and hydrogen. The oxygen given off 
by one portion of the lactic acid, therefore, must combine with the ele- 
ments of another portion, and convert it into these gases. Thus to 

1| of lactic acid . . = C9 H9 O9 
Add 12 of oxygen . . = O12 

9 of carbo- , 6 of hy- ,3 of 
nic acid "*" drogen • water. 

And we have . . . C9 H9 O21 = 9 C O2 -f 6H -f 3 HO ; 
or, while 4 atoms of lactic acid are converted into 3 of butyric acid, 1^ 
of lactic acid are at the same time converted into 9 of carbonic acid gas, 
6 of hydrogen gas, and 3 of water. The gases escape and cause the fer- 
mentation, while the water remains in the solution.* 

' I have taken in the text the smallest numbers by which the general change could be re- 
presented in the simplest way. According to Pelouze and Gelis, however, the hydrogen 
given off IS sensibly one-third of the bulk of the carbonic acid when the butyric fermenta- 
tion is m Its vigour. To satisfy this condition, therefore, much higher numbers must be 
taken ; such as the following : — 

20 of lactic acid = Ciyo H120 O120 are converted into 

15 of butync Eicid = C120 Hi2o Oeo 

Givingoff = Oeo 

And these 60 of oxygen decompose 6 of lactic acid, as above described Thus to 

6 of lactic C36 H36 036 

Add 60 of oxygen . . Oeo 

6 of carbonic acid + 12 hydrogen + 24 water. 
And we have . . C36 H36 0% = 36C02 -|. ]2H + 24HO 

where the carbonic acid gas is exactly three times the bulk of the hydrogen gas produced. 



or THE RANCIDITV OF BUTTER. 563 

The butyric acid thus produced is a colourless transparent volatile 
liquid, which emits a mingled odour of vinegar and of rancid butter. 
To the production and presence of this acid, therefore, in the milk or 
cream or in the manufactured butter, the rancidity of this important 
dairy product is partly to be ascribed. 

2°. Relation to the fatty bodies.— -It is probable that in certain cir- 
cumstances the casein of milk is capable of inducing chemical changes 
in the fatty bodies as well as m the sugars, but this conjecture has not, 
as yet, been verified by rigorous experimental investigation. 

3°. Relation to fats and sugars mixed. — It is knonrn, however, to act 
upon fatty bodies when mixed with sugar. Thus, if a small quantity 
of casein be added to a solution of sugar, lactic acid is produced for a 
certain length of time, but it ceases to be sensibly formed before the 
whole of the sugar is transformed into this acid. If now a quantity of 
oily matter be added to the mixture, the production of lactic acid will re- 
commence, and may continue till all the sugar is changed. If more 
sugar be added by degrees, the formation of acid will go on again, and, 
after a while, will cease. The introduction of a little more oil will again 
give rise to the production of acid, and, at length, the acid will cease to 
be formed, while both sugar and oil are present. The casein originally 
added has now produced its full effect (Lehmann). 

It appears, therefore, that in the presence of sugar, casein is capable 
of changing or decomposing the fatty bodies also, and of giving birth to 
oily acids of various kinds. Now, in milk, in cream, and in butter, the 
casein is mixed with the sugar of the milk and the fats of the butter, and 
thus is in a condition for changing at one and the same time both the 
sugar into lactic or butyric acid, and the butter into other acids of a 
fattv kind. Among those latter into which the butter-oil is convertible 
may probably be reckoned the capric and caproic acids, which are still 
more unpleasant to the smell and taste than the butyric acid, and which 
are known to be present in rancid butter. 

§ 16. O/" the rancidity and preservation of butter. 

We are now prepared, in some measure, to understand the changes 
that take place when butter becomes rancid — and the way in which those 
substances act which are usually employed for preserving it in a sweet 
and natural state. 

1°. When butter becomes rancid, there are two substances which 
change— the fatty matters and the milk sugar with which they are mixed. 
There are also two agencies by which these changes are induced—the 
casein present in butter, and the oxygen of the atmosphere. The quantity 
of casein or cheesy matter which butter usually contains is very small, 
but, as we have seen, it is the singular property of this substance to in- 
duce chemical changes of a very remarkable kind, upon other compound 
bodies, even when mixed with them in very minute quantity. 

2°. As it comes from the cow, this substance, casein, produces no 
change on the sugar or on the fatty matters of the milk. But after a 

Every chemist is aware, however, that in decompo4(ions of this kind, it is seldom 
that one single product is obtained alone. Though the above formula, therefore, represents 
trSv how butyric acid maybe produced from lactic acid under the circumstances yet 
other substances are not unfrequently formed durmg the actual experiment, by whi6h the 
resuit is more or loss complicated. 
24* 



564 INrLUENCE OF THE CHEESY MATTES. 

short exposure to the air it alters in some degree, and acquires the power 
of transforming milk sugar into lactic acid. Hence, as we have seen, the 
milk begins speedily to become sour. Further changes follow, and, 
among other substances, butyric acid is formed. 

In butter tlie same changes take place. The casein alters the sugar 
and the fatty matters, producing the butyric and other acids, to which its 
rancid taste and smell are to be ascribed. 

In the manufacture of butter, therefore, it is of consequence to free it as 
completely as possible from the curd and sugar of milk. This is done 
in some dairies by kneading and pressing only ; in others, by washing 
with cold water as long as the latter comes off" milky. The washing 
must be the most elFective method, and is very generally recommended 
for butter that is to be eaten fresh. In some dairies, however, it is care- 
fully abstained from, in the case of butter which is to be salted for long 
keeping. 

There are two circumstances which, in the case of butter that is to be 
kept for a length of time, may render it inexpedient to adopt the method 
of washing. The water may not be of the purest kind, and thus may 
be fitted to promote the future decomposition of the butter. Sprengel 
says that the water ought to contain as little lime as possible, because 
the butter retains the lime and acquires a bad taste from it. 

But the water may also contain organic substances in solution — vege- 
table or animal matters not visible perhaps, yet usually present even in 
spring water. These the butter is sure to extract, and they may mate- 
rially contribute to its after-decay, and to the difficulty of preserving it 
from rancidity. 

Again, the washing with water exposes the particles of the butter to 
the action of the oxygen of the atmosphere much more than when the 
butter is merely well squeezed. The effect of this oxygen, in altering 
either the fatty matters themselves or the small quantity of casein which 
remains mixed with them, may, no doubt, contribute to render some but- 
ters more susceptible of decay. 

3°. But the casein, after it has been a still longer time or more fully 
exposed to the air, undergoes a second alteration, by which its tendency 
to transform the substances with which it may be in contact, is consi- 
derably increased. It acquires the property also of inducing chemical 
changes of another kind, and it is not improbable that the more un- 
pleasant smelling capric and caproic acids may be produced during this 
period of its action. 

In the preservation of butter, therefore, for a length of time, it is of 
indispensable necessity that the air should be excluded from it as com- 
pletely as possible. In butter that is to be salted also, it is obvious that 
the sooner the salt is applied and the whole' packed close, the better and 
sweeter the butter is likely to remain. 

4°. The action of this cheesy matter, and its tendency to decay, are 
arrested or greatly retarded by the presence o^ saturated solutions of cer- 
tain saline and other substances. Of this kind is common salt, which is 
most usually employed for the purpose of preserving butter. Saltpetre, 
also, possesses this proper^ in a less degree, and is said to impart to the 
butter an agreeable flavour. A syrup or strong solution of sugar will 
likewise prevent both meat and butter from becoming rancid. Like salt- 



tfOW TO PURIFY SALT FOR BUTTEK. 565 

petre, however, it is seldom used alone, but it is not uncommon to em- 
ploy a mixture of common salt, saltpetre, and sugar, for the preservation 
of butter. Where the butter has been washed, this admixture of cane- 
sngar may supply the place of the milk-sugar which the butter originally 
contained, and may impart to it a sweeter taste. 

The salt should be as pure as possible, as free, at least, from lime and 
magnesia as it can be obtained, since these substances are apt to give 
it a bitter or other disagreeable taste. It is easy, however, to purify the 
common salt of the shops from these impurities by pouring a couple of 
quarts of boiling water upon a stone or two of salt, stirring the whole 
well about, now and then, for a couple of hours, and afterwards straining 
it through a clean cloth. The water which runs through is a saturated 
solution of salt, and contains all the impurities, but may be used for com- 
mon culinary purposes or may be mixed with the food of the cattle. 
The salt which remains on the cloth is free from the soluble salts of lime 
and magnesia, and may be hung up in the cloth till it is dry enough to 
be used for mixing with the butter or witli cheese. 

The quantity of salt usually employed is from g^-th to /gth part of the 
weight of the butter — with which it ought to be well and thoroughly in- 
corporated. The first sensible effect of the salt is to make the butter 
shrink and diminish in bulk. It becomes more solid and squeezes out a 
portion of the water — with which part of the salt also flows away. It is 
not known that the casein actually combines with the salt, nor, if it did, 
considering the very small quantity of this substance which is present in 
butter, could much salt be required for this purpose. But the points to 
attend to in the salting of butter are to take care that all the water which 
remains in the butter shall be fully saturated with salt — that is to say, 
shall have dissolved as much as it can possibly take up — and that in no 
part of the butter shall there be a particle of cheesy matter which is not 
also in contact with salt. If you exclude the air, the presence of a sat-, 
urated solution of salt will not only preserve this cheesy matter from it- 
self undergoing decay, but will render it unable also to induce decay in 
the sugar and fat which are in contact with it.* 

It is really extraordinary that such rigid precautions should be neces- 
sary to prevent the evil influence of half a pound of cheesy matter, or less, 
in a hundred pounds of butter (p. 551). 

5°. Though the curd or casein appears to be the enemy against whose 
secret machinations the dairy farmer has chiefly to guard, yet the oxygen 
of the atmosphere is a second agent by which the fatty matters of butter 
are liable to be brought into a state of decomposition, and the presence 
of which, therefore, should be excluded as carefully as possible. 

We have seen that by the action of oxygen the solid margaric acid of 
butter may be changed into the oleic or liquid acid of butter (p. 560.) 

' Mr. Ballantyne thus describes the method of salting butter practised at his dairy farm of 
30 cows, near Edinburgh :— " The butter is drawn warm from the churn, and it is an invari- 
able rule never to wash it or dip it into loater, when intended to be salted. 'I'he dairymaid 
puts it into a clean tub, which is previously well rinsed with cold water, and then works it 
with cool hands till all the milk is thoroughly squeezed out. Half the allowed quantity of 
salt is then added, and well mixed up with the buiter, and in this state it is allowed to stand 
till next morning, when it is again wrouglit up, any brine squeezed out, and the remainder 
of the salt added. It is then packed into kits, which, when full, should be well covered up, 
and placed in a cool dry store — a small quantity of salt is usually sprinkled on the surface. 
The proportion of salt used at this dairy is half a-pound to fourteen pounds of butter." — 
Journal oj Agriculture, New Series, vol. J. , p. 26. 



566 EVIL EFFECT OF THE AIR UPON BUTTER. 

This is the first, stage in the decomposition, which, when once begun, 
generally spreads or extends with increasing rapidity.* 

Again, I have also stated that this fluid (oleic) acid of butter absorbs 
oxygen with great rapidity from the air (p. 560), and changes rapidly into 
other compounds. This is the second stage, and is succeeded by others, 
which it is unnecessary to enumerate. 

To this action of the air is partly to be ascribed that peculiar kind of 
rancidity, which, without penetrating into the interior of well packed 
butter, is yet perceptible on its external surface, wherever the air has 
come in contact with it. A knowledge of this action of the atmosphere, 
therefore, urges strongly the necessity of closely incorporating and knead- 
ing together the butter in the cask or firkin — that no air holes or openings 
for air be left — that the cask itself be not only water-tight but air-tight — 
and that it should never be finally closed till the butter has shrunk in as 
far as it is likely to do, and until the vacancies, which may have 
arisen between the butter and the cask, have been carefully filled up 
again. 

§ 17. Of the natural and artificial curdling of milk. 

When milk is left to itself for a certain length of time it becomes sour 
and curdles. The curd and whey, however, do not readily separate un- 
less a gentle heat be applied, when the curd contracts in bulk, and either 
squeezes out and floats upon the whey, or, when cut into pieces or placed 
in a perforated cheese-vat, allows the whey freely to flow from it. If 
the mixed curd and whey from the entire milk be allowed to simmer for 
a length of time at a slow fire, the buttery part will separate from the 
cheese, and will float on the top in the form of a fluid oil. 

1°. Natural curdling. — The natural curdling of milk is produced by 
the lactic acid, which, as we have seen (p. 544), is always formed from 
the milk-sugar when milk is allowed to stand for any length of time in 
the air. It does not curdle immediately upon becoming sour, for a reason 
which I shall presently explain. 

2°. Artificial curdling. — But it is not usual in the manufacture of 
cheese to allow the milk to sour and curdle of its own accord. The pro- 
cess is generally hastened by the artificial addition of acid, or of some 
substance, such as rennet, by which the natural production of acid is ac- 
celerated. Almost any acid substance will have the effect of curdling 
milk. Muriatic acid (spirit of salt), diluted with water, is said to be ex- 
tensively, though not universally, employed in Holland for this pur- 
pose. In other countries vinegar,f tartaric acid, lemon juice, cream of 

* I do not know whether a converse change is ever observed in butter by long keeping in 
contact with brine — whether it ever becomes very sensibly harder. Tallow, as is well 
known to candle-makers, and especially to the manufacturers of stearin candles, becomes 
harder by keeping, indeed sometimes is unfit for use until it is a year old — candles in a damp 
place become harder by keeping — and in tallow that has lain long in a wet mine the oily part 
has been found entirely changed into the solid fat of tallow (Beetz). A similar change, 
therefore, is not impossible nor inexplicable in butter also — only if it ever do take place, we 
should expect the changed butter to be less solid and dense than before. 

t " To coagulate a cotyla of milk we add a cyathus of sweet vinegar" (Dioscorides). Milk 
is also curdled by ardent spirits, by the juice of the fig, and by a decoction of the flowers of 
the artichoke, of the white and' yellow bed-straw (.galium), and of the crowfoot (ranunculus 
Jlammula and Ungula). The Tuscan ewe-cheese is curdled with the juice of the fresh, or 
with a decoction of the dried flowers of the wild thistle, or with the flowers of the artichoke, 
which gives a cheese of finer colour and less pungent taste. 



i 



NATURAL AND ARTIFICIAL CURDLING OF MILK. 567 

tartar, and salt of sorrel have been occasionally used, and in Switzerland 
— especially in the manufacture of the schabzieger cheese — it is cus- 
tomary to add merely a little sour milk for the purpose of producing the 
curd. 

3°. Ckeynical action of the acid. — But how does the acid act in causing 
the milk to curdle, and why is it necessary to allow a little time to 
elapse and to apply also a gentle heat before the curd will completely 
separate ? 

In regard to casein or the cheesy matter of milk, we Ixave seen (p. 
561)— 

a. That though nearly insoluble in pure water, it dissolves readily in 
water containing in solution a small quantity of potash or soda, either in 
the caustic or carbonated state. In other words the casein, which is an 
acid substance, unites chemically with the potash or the soda, and forms 
a compound which is soluble in water. 

h. That when an acid is added to this solution, it takes the potash or 
soda from the casein and combines with it, leaving the curd again in its 
original insoluble state, and causing it, therefore, to separate from the 
water. 

Now in milk, as it comes from the cow, the casein is in chemical 
combination with a small quantity of soda, by which it is rendered so- 
luble in the water of which the milk chiefly consists. When the milk 
stands for a time in the air, the sugar of milk, as we have seen, is trans- 
formed into lactic acid — this acid takes the soda from the casein, and 
forms lactate of soda, and the cheesy matter, in consequence, being itself 
insoluble in water, separates in the form of curd. The application of a 
gentle heat acts in two ways. It aids the acid in more completely taking 
the soda from the casein, and causes the latter at the same time to 
shrink in, to become less bulky, and thus to separate readily from the 
whey. 

If we add an acid artificially to milk, the effect is exactly the same. 
Either muriatic acid, or tartaric acid, or vinegar, or sour milk, will, in the 
same way, take the soda from the casein, and render it insoluble. And 
that this is the true action is readily proved by adding a little soda to 
curdled milk, when the curd will be re-dissolved, and the milk will be- 
come sweet. Add acid to it now, or let it sour naturally a second time, 
and the curd will again be separated. 

The action of rennet is in some degree different, though no less simple 
and beautiful. Let us first, however, consider what rennet is, and how 
it is prepared. 

§ 18. Of the preparation of rennet. 

Rennet is prepared from the salted stomach or intestines of the suck- 
ling calf, the utiweaned lamb, the young kid, or the young pig-* In 
general, however, the stomach of the calf is preferred, and there are 
various ways of curing and preserving it. 

1°. Preparing the stomach. — The stomach of the newly killed animal 
contains a quantity of curd derived from the milk on which it has been 
fed. In most districts (Switzerland, Gloucester, Cheshire) it is usual to 

* Dried pig^s bladder is often employed instead of the dried kid's stomach for curdling the 
goat's milk on Mont Dor. 



568 METHODS OF MAKING THE RENNET. 

remove by a gentle washing the curd and slimy matters which are pre- 
sent in the stomach, as they are supposed to impart a strong taste to the 
cheese. • In Cheshire the curd is frequently salted separately for imme- 
diate use. In Ayrshire and Limburg, on the other hand, the curd is 
always left in the stomach and salted along with it. Some even give 
the calf a copious draught of milk shortly before it is killed, in order that 
the stomach may contain a larger quantity of the valuable curd. 

2°. Salting the stomach.— In the mode of salting the stomach similar 
differences prevail. Some merely put a few handfuls of salt into and 
around it, then roll it together, and hang it near the chimney to dry. 
Others salt it in a pickle for a few days, and then hang it up to dry 
(Gloucester), while others again (Cheshire) pack several of them in 
layers with much salt both within and without, and preserve them in a 
cool place till the cheese-making season of the following year. They 
are then taken out, drained from the brine, spread upon a table, sprinkled 
with salt which is rolled in with a wooden roller, and then hung up to 
dry. In some foreign countries, again, the recent stomach is minced very 
fine, mixed with some spoonfuls of salt and bread-crumb into a paste, 
put into a bladder, and then dried. In Lombardy the stomach, after 
being salted and dried, is minced and mixed up with salt, pepper, and a 
little whey or water into a paste, which is preserved for use. [Cattaneo, 
II latte e i suoi prodotti, p. 204.] 

In whatever way the stomach or intestine of the calf is prepared and 
preserved, the almost universal opinion seems to be, that it should be 
kept for 10 or ] 2 months before it is capable of yielding the best and 
strongest rennet. If newer than 12 months, the rennet is thought in 
Gloucestershire " to make the cheeses heave or swell, and become full 
of eyes or holes." [British Husbandry, ii., p. 420.] 

3°. Making the rennet. — In making the rennet different customs also 
prevail. In some districts, as in Cheshire, a bit of the dried stomach is 
put into half a pint of lukewarm water with as much salt as will lie 
upon a shilling, is allowed to stand over night, and in the morning the 
infusion is poured into ihe milk. For a cheese of 601bs. weight, a piece 
of the size of half-a-crown will often be sufficient, though of some skins 
as much as 10 square inches are required to produce the same effect [Dr. 
Holland.] 

It is perhaps more common, however, to take the entire stomach 
{dried-maws, veils, reeds, or yirning* they are often called), and to pour 
upon them from one to three quarts of water for each stomach, and to 
allow them to infuse for several days. If only one has been infused, and 
the rennet is intended for immediate use, the infusion requires only to be 
skimmed and strained. But if several maze- skins be infused — or, as is 
the custom in Cheshire, as many as have been provided for the whole 
season — about two quarts of water are taken for each, and, after stand- 
ing not more than two days, the infusion is poured off', and is completely 
saturated with salt. During the summer it is constantly skimmed, and 
fresh salt added from time to time. Or a strong brine may at once 

• In Northumberland the dried stomach is sometimes called the keslap, which is evidently 
the German k'dse-lab, cheese-rennet. Loppert and lajrpert, applied in Northumberland and 
the West of Scotland respectively to sour, curdled milk, is derived from the same German 
lab, rennet, or later, to coagulate. 



THEORY OF THE ACTION OF RENNET. 569 

be poured upon the skins, and the infusion, when the skins are taken 
out, may be kept for a length of time. Some even recommend that 
the liquid rennet should not be used until it is at least tv/o months old. 
When thus kept, however, it is indispensable that the water should be 
fully saturated with salt. 

In Ayrshire, and in some other counties, it is customary to cut the 
dried stomach into small pieces, and to put it, with a handful or two of 
salt and one or two quarts of water, into a jar, to allow it to stand for two 
or three days, afterwards to pour upon it another pint for a couple of days, 
to mix the two decoctions, and, when strained, to bottle the whole for 
future use. In this state it may be kepi for many months.* 

In all the methods above described, the exhausted skins are thrown 
away. Where they are cut into pieces, as in Cheshire and Ayrshire, 
they cannot of course be put to any second use, but where they are steeped 
whole, there is every reason to believe that they might be used with al- 
most equal advantage a second or even a third time. Accordingly, it 
has long been the custom in the north of England to re-salt the stomach 
after it has been once steeped, and when long dried, as before, to use it 
a second and even a third time for the preparation of rennet. When we 
explain the mode in which rennet acts, you will see that the same skin 
may, with good reason, be expected to yield a good rennet, after being 
salted again and again for an indefinite number of times. 

In making rennet, some use pure water only, others prefer clear whey, 
others a decoction of leaves — such as those of the sweetbriar, the dog- 
rose, and the bramble— or of aromatic herbs and flowers, while others, 
again, put in lemons, cloves, mace, or brandy. These various practices 
are adopted for the purpose of making the rennet keep better, of lessen- 
ing its unpleasant smell, of preventing any unpleasant taste it might 
give to the curd, or finally of directly improving the flavour of the cheese. 
The acidity of the lemon will, no doubt, increase also the coagulating 
power of any rennet to which it may be added. 

4°. How the rennet is used. — The rennet thus prepared is poured into 
the milk previously raised to the temperature of 90° or 95° F., and is 
intimately mixed with it. The quantity which it is necessary to add 
varies with the quality of the rennet — from a table-spoonful to half a 
pint for 30 or 40 gallons of milk. The time necessary for the complete 
fixing of the curd varies also from 15 minutes to an hour or even an hour 
and a half. The chief causes of this variation are the temperature of the 
milk, and the quality and quantity of the rennet employed. 

But how does the rennet act in causing this coagulation? Before 
we can answer this question it is necessary to enquire what rennet 
really is. 

§ 19. Theory of the action of rennet. 

It has been stated, and hitherto almost generally received, that the only 
effective substance contained in rennet is the gastric juice derived from 
the stomach of the calf. To this persuasion is, no doubt, to be ascribed 

* A table-spoonful of this rennet, according to Mr. Alton, will coagulate 30 gallons of milk, 
and will curdle it in five or ten minutes, wliereas the English rennet requires from one to 
three hours. This superiority he ascribes to the custom of leaving the curdled milk in the 
dtomach. He denies also that this milk gives any harsh taste to the cheese. 



570 THE SUBSTANCE Of THE STOMACH CHANGES 

the custom both of preserving the natural contents of the stomach — and 
of generally throwing away the bag after being once salted, dried, and 
extracted. The gastric juice which exudes from the interior surface of 
the stomachs of all animals is known to curdle milk readily, and, there- 
fore, it was natural to ascribe the action of rennet to the presence of this 
substance, and to infer that, being once extracted, it was in vain to ex- 
pect much advantage from salting and infusing the membrane a second 
time. But the three facts — 

a. That in most places it is customary to wash the interior of the 
stomach before salting it, and thus to remove the greater part of the gas- 
tric juice it may contain ; 

b. That besides, in many places, the bags are laid up in brine for 
weeks and months, and are then drained out of this brine before they are 
dried — by which any gastric juice remaining must be almost entirely re- 
moved, — and 

c. That after being dried and steeped once for the preparation of ren- 
net, experience. has proved that they may again be salted and used over 
again ; 

— these three facts, I think, shew that the efficacy of rennet does not de- 
pend upon any thing originally contained in the stomach, but upon 
something derived from the substance of the stomach itself. 

Now when considering the properties of milk-sugar and of lactic acid, 
I have stated that if a piece of the fresh membrane of the stomach or in- 
testine, or even of the bladder of an animal, be exposed to the air for a 
few days, and be then immersed into a solution of milk-sugar, it will 
gradually transform the sugar into lactic acid. In milk this membrane 
would produce a similar effect, aiding and hastening the natural souring 
and curdling effect of the casein. By exposure to the air, the surface of 
the membrane has undergone such a degree of change or decomposition, 
as enables it to induce the elements of the sugar to alter their mutual 
arrangement, and to unite together in such a way as to form lactic acid. 

If the moist membrane be exposed for a longer time to the air this 
change of its surface will penetrate deeper, and it will become more ef- 
fective in inducing the transformation of the sugar into lactic acid. But, 
at the same time, a portion of its surface may run into a state of putre- 
faction, and besides acquiring a disagreeable odour may become capable 
also of bringing on fermentation and putrefactive decay in the solutions 
upon which it may be made to act. It is not expedient, therefore, to at- 
tempt to heighten the transforming effect of animal membranes by 
exposing them for a greater length of time to the air in a moist and fresh 
state. 

But if the membrane be salted, and thus preserved from the rapid 
action of the air, it will be protected from putrefaction in a great degree, 
while, at the same time, it -will undergo that gradual change upon its 
surface to which its power of transforming solutions of sugar is ascribed. 
And this change will be materially hastened and increased and made to 
penetrate deeper, if the salted membrane be subsequently dried slowly 
in the air by a gentle heat, and be afterwards kept for a length of time 
where the air has more or less ready access to it. Such is the mode of 
treatment to which the calf's stomach is subjected for the preparation of 
rennet, and it is an important practical observation that the membrane 



WHEN EXPOSED A SHORT TIME TO THE AIR. S7%> 

should be kept at least 12 months, if it is to acquire very powerful 
coagulating properties. 

It is necessary further to remind you that when malt is steeped in 
water for a few minutes, a substance, named diastase, is extracted from 
it, which possesses the remarkable property of changing starch into 
sugar in a very short time, and in large quantity (p. 119). Now if this 
diastase be exposed to the air for a length of time, it undergoes a change 
similar to that experienced by the surface of animal membranes, and 
acquires the property of transforming sugar into lactic a<"id. After un- 
dergoing this change it still dissolves readily in water, and if a solution 
of it be poured into one of sugar, the transformation of the latter into lactic 
acid gradually proceeds. There exist, therefore, substances soluble in 
water, which possess the same power as slightly decayed but insoluble 
animal membrane, of converting sugar into lactic acid. 

During the protracted drying and decay of the salted stomach, the 
change undergone at length by the surface of the membrane is such as to 
produce a quantity of matter capable of dissolving in water, and which 
also possesses the property of quickly converting the sugar into the acid 
of milk. This matter, water extracts from the dried skin, and it forms 
the active ingredient in rennet. 

I need not further explain to you upon what this activity depends — 
since as you already know any thing which will rapidly change sugar 
into lactic acid, will also, if gently warmed, rapidly curdle milk (p. 
567). 

Thus the action of rennet resolves itself simply into a curdling of milk 
by the action of its own acid. It is the same thing as when sour milk 
in Switzerland is at once mixed with that from which the cheese is to be 
made ; or it is only a more speedy way of bringing about the curdling 
that takes place when milk sours naturally and is then gently warmed 
till the curd separates. 

But how, it may be asked, is the coagulation effected so much more 
rapidly by the action of rennet than when the milk is left to sour of its 
own accord ? It is because the whole of the animal matter in the rennet 
is already in the state in which it easily transforms the sugar into acid, 
and being intimately mixed with the whole milk in a warm state, it pro- 
duces acid near every particle of the cheesy matter. From this 
cheesy matter the acid formed takes away the soda that holds it in solu- 
tion, and thus renders it insoluble or curdles the raill<:. In milk, on tiie 
other hand, which is left to sour and curdle of itself, the casein must first 
be changed by the action of the air before it can transform the sugar and 
produce acid. This change takes place more or less slowly, and chiefly 
at the surface of the milk where it is in contact with the air. The sour- 
ing, therefore, must also proceed slowly, and the curdUng of which it is 
the cause. 

It is no objection to this explanation of the action of rennet, that neither 
the milk nor the whey become sensibly sour during the separation of the 
curd. The acid, as it is produced, combines directly with the soda pre- 
viously united to the curd, and renders the latter insoluble — while, if 
any excess of acid do happen to be formed, it is in great part taken up 
and retained mechanically by the curd, and thus is not afterwards sen- 
sibly perceived in the whey. 



572 USE OF THE CURD FOUND IN THE CALF's STOMACH. 

Using the same skin a second time. — If this then be a true explanation 
of the action of rennet — if the coagulating ingredient in it be merely a 
portion of the changed membrane of the stomach itself — it is obvious that 
the bag, after being once used, may be again salted and dried with ad- 
vantage. The slow decay may, after a second salting, become still 
slower, and thus it may require to be longer kept after the second than 
after the first salting, before it will give a rennet as powerful as that 
which was first extracted from it. But unless it be merely the inner 
membrane of the stomach and intestines which is capable of undergoing 
that kind of change upon which the coagulating power depends, there is 
no apparent reason, as I have already sta*ed to you, why the sSme 
maw- skin may not be salted, dried, and steeped many times over. 

Use of whey. — Again, in the maldng of rennet there seems some pro- 
priety in the use of whey rather than of water. The whey may contain 
a portion of the rennet which had been added to the milk from which 
it was extracted, and may thus be able of itself to curdle milk. It is 
sure also to contain some milk-sugar, which, being changed into acid 
when the whey is poured upon the dried stomach, will add to the coag- 
ulating power of the rennet obtained. 

Use of the curdled milk contained in the sto^nach. — Does the view we 
have taken of the action of rennet throw any light upon the use of the 
curdled milk found in the stomach? Is it of any service, or ought it to 
be rejected? 

We are certain that it must be of service in coagulating mUk, since in 
Cheshire, according to Dr. Holland, it is frequently taken out and salted 
by itself for immediate use. But a slight consideration of the properties 
of casein, as I have already stated them to you (p. 562), will explain 
why this curdy matter should be serviceable for such a purpose. 

You will recollect that casein, after being exposed to the air for a short 
time, acquires, like animal membranes, the property of converting sugar 
into lactic acid (p. 562), and of curdling milk. Now the curdy matter 
taken from the stomach of the calf, after being exposed to the air, ac- 
quires this property as completely as a more pure curd will do. If salted 
and kept, it will be changed still further, and will acquire this property 
in a greater degree. In short, keeping will affect the curd precisely in 
the same way as it does the membrane of the stomach itself, and wiU 
render it alike fit to be employed in the preparation of rennet. Nor is 
it unlikely that fresh well-squeezed curd, if mixed with much salt and 
kept in slightly covered jars for 10 or 12 months, might yield a rennet 
possessed of good coagulating properties. 

It thus appears that, so far as economy is concerned, the curdy matter 
contained in the calfs stomach ought to be preserved and salted for use. 
If in any district this curd be suspected to impart an unpleasant flavour 
to the cheese, this bad effect may probably be remedied by taking it out 
of the stomach, washing it well with water — as is done in some dairy 
districts — mixing it with salt, and then returnijig it into the stomach 
again. 

Another practical conclusion may also be drawn from this explanation 
of the action of the stomach. Since it is the membrane alone that acts, 
there can no loss accrue by carefully washing the stomach as well as 
the curd it contains. On the contrary, by so doing we may remove 



CHEESE OF DIFFERENT QUALITIES — ^HOW OBTAINED. 573 

from its inner surface some substances which, if allowed to remain, might 
afterwards act injuriously upon the flavour or upon the other qualities of 

the cheese. 

• 

§ 20. Of the circumstances by which the quality of cheese is affected. 

All cheese consists essentially of the curd mixed with a certain por- 
tion of the fatty matter and of the sugar of milk. But differences in the 
quality of the milk, in the proportions in which the several constituents 
of milk are mixed together, or in the general mode of dairy manage- 
ment, give rise to varieties of cheese almost without number. Nearly 
every dairy district produces one or more qualities of cheese peculiar to 
itself It will not be without interest to attend briefly to some of these 
causes of diversity. 

1°. Natural differences in the milk. — It is obvious that whatever gives 
rise to natural differences in the quality of the milk must affect also that 
of the cheese prepared from it. If the milk be poor in butter, so must 
the cheese be. If the pasture be such as to give a milk rich in cream, 
the cheese will partake of the same quality. If the herbage or other food 
affect the taste of the milk or cream, it will also modify the flavour of the 
cheese. 

2°. Milk of different animals. — So the milk of different animals 
will give cheese of unlike qualities. The ewe-milk cheeses of Tuscany, 
Naples, and Languedoc, and those of goat's milk made on Mont Dor 
and elsewhere, .are celebrated for qualities which are not possessed by 
cheeses prepared from cow's milk in a similar way. Buffalo milk also 
gives a cheese of peculiar qualities, which is manufactured in some parts 
of the Neapolitan territory. 

Other kinds of cheese agam are made from mixtures of the milk of dif- 
ferent animals. Thus the strong tasted cheese of Lecca and the cele- 
brated Roquefort cheese are prepared from mixtures of goat with ewe- 
milk, and the cheese of Mont Cenis* from both of these mixed with the 
milk of the cow.f 

3°. Creamed or uncreamed milk. — Still further differences are pro- 
duced according to the proportion of cream which is left in or is added to 
the milk. Thus if cream only be employed, we have the rich cream- 
cheese which must be eaten in a comparatively recent state. Or, if the 
cream of the previous night's milking be added to the new milk of the 
morning, we may have such (jheese as the Stilton of England, or the 
small, soft, and rich Brie cheeses, so much esteemed in France. If the 
entire milk only be used, we have such cheeses as the Cheshire, the 
Double Gloucester, the Cheddar, the Wiltshire, and the Dunlop cheeses 
of Britain, the Kinnegad cheese, I believe, of Ireland, and the Goudaand 
Edam cheeses of Holland. Even here, however, it makes a difference 
whether the warm milk from the cow is curdled alone, as at Gouda and 
Edam, or whether it is mixed with the milk of the evening before, as is 
generally done in Cheshire and Ayrshire. Many persons are of opin- 
ion that cream, which has once been separated, can never be so well 

* Lecca i^ a province in the Eastern part of the Neapolitan territory ; Roquefort, a town 
in the pastoral department of Aveiron, in the South of France, famed for its sheep; and 
Mont Cenis, a mountain in Savoy. 

t The milk of 2 goats is mixed with that of 20 sheep and 5 cows. 



574 BUTTER-MILK, WHEY, AND VEGETABLE CHEESES^. 

mixed again with the milk, that a portion of the fatty matter shall not 
flow out with the whey and render the cheese less rich. 

If, again, the cream of the evening's milk be removed, and the skim- 
med milk added to the new milk of the next morning, such cheeses as 
the Single Gloucester are obtained. If the cream be taken once from 
all the milk, the better kinds of skimmed-milk cheese, such as the Dutch 
cheese of Leyden, are prepared — while if the milk be twice skimmed, 
we have the poorer cheeses of Friesland and Groningen. If skimmed 
for three or four days in succession, we get the hard and horny cheeses 
of Essex and Sussex, which often require the axe to break them up. 

4°. Butter-milk cheese. — But poor or butterless cheese will also differ 
in quality according to the state of the milk from which it is extracted. 
If the new milk be allowed to stand to throw up its cream, and this be 
then removed in the usual way, the ordinary skimmed-milk cheese will 
be obtained by adding rennet to the milk. But if, instead of skimming, 
we allow the milk to- stand till it begins to sour, and then remove the 
butter by churning the whole, we obtain the milk in a sour state {butter- 
milk). From this milk the curd separates naturally by gentle heating. 
But being thus prepared from sour milk and without the use of rennet, 
butter-milk cheese differs more or less in quality from that which is made 
from sweet skimmed milk. 

The acid in the butter-milk, especially after it has stood a day or two, 
is capable of coagulating new milk also, and thus, by mixing more or 
less sweet milk with the butter-milk before it is warmed, several other 
qualities of mixed butter and sweet milk cheese may readily be manu- 
factured. 

If, as is stated by Mr. Ballantyne, the churning of the whole milk 
gives butter in larger quantity, of better quality, and more uniformly 
throughout the whole year (p. 556), the manufacture of these butter-milk 
cheeses is deserving of the attention of dairy farmers, especially in those 
districts where butter is considered as the most important produce. 

5°. Whey-cheese. — The whey which separates from the curd, and 
especially the white whey, which is pressed out towards the last, contains 
a portion of curd, and not unfrequently a considerable quantity of butter 
also. When the whey is heated, the curd and butter rise to the surface, 
and are readily skimmed off. This curd alone will often yield a cheese 
of excellent quality, and so rich in butter, that a very good imitation of 
Stilton cheeee may sometimes be made with alternate layers of new 
milk-curd and this curd of whey. 

•6°. Mixtures of vegetable substances ivith the milk.- — New varieties 
of cheese are formed by mixing vegetable substances with die curd. A 
green decoction of two parts of sage-leaves, one of marigold, and a httle 
pcirsley, gives its colour to the green cheese of Wiltshire ; some even mix 
up the entire leaves with the curd. The celebrated Schabzieger cheese 
of Switzerland is made by crushing the skim-milk cheese after it is se- 
veral months old to fine powder in a mill, mixing it then with one-tenth 
of its weight of fine salt and one-twentieth of the powdered leaves of the 
mellilot trefoil {trifolium melilotus cerulea),, and afterwards with oil or 
butter — working the whole into a paste, which is pressed and carefully 
dried. 

Potato cheeses,, as they are called, are made in various ways. One 



TEMPERATURE AND HEATING OF THE MILK. 575 

pound of sour milk is mixed with five pounds of boiled potatoes and a 
little salt, and the whole is beat into a pulp, which, after standing five or 
six days, is worked up again, and then dried in the usual way. Others 
mix three parts of dried boiled potatoes with two of fresh curd, or equal 
weights, or more curd than potato according to the quality required. 
Such cheeses are made in Thuringia, in Saxony, and in other parts of 
Germany. In Savoy, an excellent cheese is made by mixing one of the 
pulp of potatoes with three of ewe milk curd, and in Westphalia a po- 
tato cheese is made with skimmed milk. This Westphalian cheese, 
while in the pasty state, is allowed to undergo a certain extent of fer- 
mentation before it is finally worked up with butter and salt, made into 
shapes and dried. The extent to which this fermentation is permitted to 
go determines the flavour of the cheese. 

§ 21. Circumstances under which cheese of different qualities may be 
obtained from the same milk. 

But from the same milk, in the same state, different kinds or qualities 
of cheese may be prepared according to the way in which the milk or 
the curd is treated. Let us consider also a few of the circumstances by 
which this result may be brought about. 

1 °. Temperature to which the milk is heated. — The temperature of new 
or entire milk, when the rennet is added, should be raised to about 95° F. 
— that of skimmed milk need not be quite so high. If the milk be 
warmer the curd is hard and tough, if colder, it is soft and difficult to ob- 
tain free from the whey. When the former happens to be the case, a 
portion of the first whey that separates may be taken out into another 
vessel, allowed to cool, and then poured in again. If it prove to have 
been too cold, hot milk or water may be added to it — or a vessel contain- 
ing hot water may be put into it before the curdling commences — or the 
first portion of whey that separates may be heated and poured again 
upon the curd. The quality of the cheese, however, will always be 
more or less affected when it happens to be necessary to adopt any of 
these remedies. To make the best cheese, the true temperature should 
always be attained as nearly as possible, before the rennet is added. 

2°. Mode in which the milk is wanned. — If, as is the case in some 
dairies, the milk be warmed in an iron pot upon the naked fire, great care 
must be taken that it is not singed or Jirefanged. A very slight inat- 
tention may cause this to be the case, and the taste of the cheese is sure 
to be more or less affected by it. In Cheshire the milk is put into a large 
tin pail, which is plunged into a boiler of hot water, and frequently stir- 
red till it is raised to the proper temperature. In large dairy establish- 
ments, however, the safest method is to have a pot with a double bottom, 
consisting of one pot witMn another — after the manner of a glue-pot — the 
space between the two being filled with water. The fire applied be- 
neath thus acts only upon the water, and can never, by any ordinary 
neglect, do injury to the milk. It is desirable in this heating, not to raise 
the temperature higher than is necessary, as a great heat is apt to give 
an oiliness to the fatty matter of the milk. 

3°. The time during which the curd stands is also of importance. It 
should be broken up as soon as the milk is fully coagulated. The longer 
it stands after this the harder and tougher it will become. 



576 QUALITY AND QUANTITY OF THE RENNET. 



i 



4°. The quality of the rennet is of much importance not only in regard 
to the certainty of the coagulation, but also to the flavour of the cheese. 
In some parts "of Cheshire, as we have seen, it is usual to take a piece 
of the dried membrane and steep it overnight with a little salt for the 
ensuing morning's milk. It is thus sure to be fresh and sweet if the 
dried maw be in good preservation. But where it is customary to steep 
several skins at a time, and to bottle the rennet for after-use, it is very- 
necessary to saturate the solution completely with salt and to season it 
with spices, in order that it may be preserved in a sweet and wholesome 
state. In some parts of Scotland the rennet is said to be frequently kept 
in bottles till it is almost putrid, and in this state is still put into the milk. 
Such rennet may not only impart a bad taste to the cheese, but is likely 
also to render it more difficult to cure and to bring on putrefaction after- 
wards and a premature decay. 

5°. The quantity of rennet added ought to be regulated as carefully 
as the temperature of the milk. Too much renders the curd tough ; too 
little causes the loss of much time, and may permit a larger portion of 
the butter to separate itself from the curd. It is to be expected also that 
when rennet is used in great excess, a portion of it will remain in the 
curd, and will naturally affect the kind and rapidity of the changes it 
afterwards undergoes. Thus it is said to cause the cheese to heave or 
swell out from fermentation. It is probable also that it will affect the 
flavour which the cheese acquires by keeping. Thus it may be that the 
agreeable or unpleasant taste of the cheeses of certain districts or dairies 
may be less due to the quality of the pastures or of the milk itself, than 
to the quantity of rennet with which it has there been customary to co- 
agulate the milk. 

6*^. The way in which the rennet is 7nade, no less than its state of pre- 
servation and the quantity employed, may also influence the flavour or 
other qualities of the cheese. For instance, in the manufacture of a 
celebrated French cheese — that of Epoisse — the rennet is prepared as fol- 
lows : — Four fresh calf-skins, with the curd they contain, are well 
washed in water, chopped into small pieces, and digested in a mixture 
of 5 quarts of brandy with 15 of water, adding at the same time 2^ lbs. 
of salt, half an ounce of black pepper, and a quarter of an ounce each 
of cloves and fennel seeds. At the end of six weeks the liquor is filtered 
and preserved in well corked bottles, while the membrane is put into salt- 
water to form a new portion of rennet. For making rich cheeses, the 
rennet should always be filtered clear. [II latte e i suoi prodotti, p. 274.] 

Again, on Mont Dor, the rennet is made with white vidne and vinegar. 
An ounce of common salt is dissolved in a mixture of half a pint of 
vinegar with 2§ pints of white wine, and in^his solution a prepared 
goat's stomach or a piece of dried pig^s bladder is steeped foralength of 
tune. A single spoonful of this rennet is said to be sufficient for 45 or 
50 quarts of milk. No doubt the acid of the vinegar and of the wine aid 
the coagulating power derived from the membrane. 

Rennets prepared in the above ways must affect the flavour of the 
cheese differently from such as are obtained by the several more or less 
careful methods usually adopted in this country. 

7°. When acids are used alone — as vinegar, tartaric acid, and muria- 
tic acid sometimes are — for coagulating the milk, the flavour of the 



now THE WHEY IS SEPARATED. 677 

cheese can scarcely fail to be in some measure difTerent from that, which 
is prepared with ordinary rennet. 

8°. The tvay in which the curd is treated. — It is usual in our best 
cheese districts carefully and slowly to separate the curd from the whey — 
not to hasten the separation, lest a larger portion of the fatty matter should 
be squeezed out of the curd and the cheese should thus be rendered poorer 
than usual. But in some places the practice prevails of washing the 
curd with hot water after the whey has been partially separated from it. 

Thus at Gouda in Holland, after the greater part of the whey has been 
gradually removed, a quantity of hot water is added, and allowed to re- 
main upon it for at least a quarter of an hour. The heat makes the 
cheese more solid and causes it to keep better. 

In Italy, again, the so-called pear-shaped caccio-cavallo cheeses and 
the round palloni cheeses of Gravina, in the Neapolitan territory, are 
made from curd, which, after being scalded with boiling whey, is cut into 
slices, kneaded in boiling water, worked with the hand till it is perfectly 
tenacious and elastic, and then made into shapes. The water in which 
the curd is washed, after standing 24 hours, throws up much oily mat- 
ter, which is skimmed off and made into butter. 

The varieties of cheese prepared by these methods no doubt derive the 
l^eculiar characters upon which their reputation depends from the treat- 
ment to which the curd is subjected — but it is obvious that none of them 
can be so rich as a cheese from the same milk would be, if manufactured 
in a Cheshire, a Wiltshire, or an Ayrshire dairy. 

9°. The separation of the whey is a part of the process upon which the 
quality of the cheese in a considerable degree depends. In Cheshire 
more time and attention is devoted to the perfect extraction of the whey 
than in almost any other district. Indeed, when it is considered that the 
whey contains sugar and lactic acid, which may undergo decomposition, 
and a quantity of rennet which may bring on fermentation — by both of 
which processes the flavour of the cheeses must be considerably affected 
— it will appear of great importance that the whey should be as com- 
pletely removed from the curd as it can possibly be. To aid in effecting 
this a curd-mill, for chopping it fine after the whey is strained off, is in 
use in many of the large English dairies, and a very ingenious, and I 
believe efTectual, pneumatic cheese-press for sucking out the whey was 
invented by the late Sir John Robinson, of Edinburgh. [Transactions 
and Prize Essays of the Highland Society, vol. x., p. 204.] 

But the ivay in which the whey is separated is not a matter of indif- 
ference, and has much influence upon the quality of the cheese. Thus 
in Norfolk, according to Marshall, when the curd is fairly set, the dairy- 
maid bares her arm, plunges it into the curd, and with the help of her 
wooden ladle breaks up minutely and intimately mixes the curd with the 
whey. This she does for 10 or 15 minutes, after which the curd is al- 
lowed to subside, and the whey is drawn ofT. By this agitation 
the whey must carry off more of the butter and the cheese must be 
poorer. 

In Cheshire and Ayrshire, again, the curd is cut with a knife, butx is 
gently used and slowly pressed till it is dry enough to be chopped tine, and 
thus more of the oily matter is retained. On tlie same principle, in making 
the Stilton cheese, the curd is not cut or broken at all, but is pressed 



578 RIND OF SALT, AND HOW IT IS APPLIED. H 

gently and with care ti]l the whey gradually drains out. Thus the butter 
and the curd remain intermixed, and the rich cheese of Stilton is the result. 

Thus you will see that while it is of importance that all the whey 
should be extracted from the curd, yet that the quickest v/ay may not be 
the best. More time and care must be bestowed in order to effect this 
object, the richer the cheese we wish to obtain. You will see, also, how 
the quality of the milk or of the pastures may often be blamed for de- 
ficiencies in the ricliness or other qualities of our cheese, which are 
in reality due to slight but material differences in our mode of manufac- 
turing it. 

10°. The kind of salt used is considered by many to have some effect 
upon the taste of the cheese. Thus the cheese of Gerome, in the Vos- 
ges, is supposed to derive a peculiar taste from the Lorena salt with 
which it is cured. In Holland, also, the efficacy of one kind of salt 
over another for the curing of cheese is generally acknowledged, [British 
Husbandry, ii., p. 424.] It is indeed not unlikely that the more or less 
impure salts of different localities may affect the flavour of the cheese, 
but wherever the salt may be manufactured, it is easy to obtain it in a 
uniform and tolerably pure state, by the simple process of purification, 
which I have already described to you (p. 565.) 

11°. The mode in which the salt is applied. — In making the large 
Cheshire cheeses the dried curd, for a single cheese of 60 lbs., is broken 
down fine and divided into three equal portions. One of these is 
mingled with double the quantity of salt added to the others, and this 
is so put into the cheese-vat as to form the central part of the cheese. 
By this precaution the after-salting on the surface is sure to penetrate 
deep enough to cure effectually the less salted parts. In the counties of 
Gloucester and Somerset the curd is pressed without salt, and the cheese, 
when formed, is made to absorb the whole of the salt afterwards through 
its surface. This is found to answer well with the small and thin 
cheeses made in these counties, but were it adopted for the large cheeses 
of Cheshire and Dunlop, or even for the pine-apple cheeses of Wiltshire, 
there can be no doubt that their quality would frequently be injured. It 
may not be impossible to cause salt to penetrate into the very heart of a 
large cheese, but it cannot be easy in this way to salt the whole cheese 
equally, while the care and attention required must be greatly increased. 

12°. Addition of cream or butter to the curd. — Another mode of im- 
proving the quality of cheese is by the addition of cream or butter to the 
dried and crumbled curd. Much diligence, however, is required fully 
to incorporate these, so that the cheese may be uniform throughout. Still 
this practice gives a peculiar character to the cheeses of certain districts. 
In Italy they make a cheese after the manner of the English, [II latte e i 
suoi prodotti, p. 277], into which a considerable quantity of butter is 
worked ; and the Reckem cheese of Belgium is made by adding half an 
ounce of butter and the yoke of an egg to every pound of pressed curd. 

13°. The colouring matter added to the cheese is thought by many to 
affect its quality. In foreign countries saffron is very generally used to 
give a colour to the milk before it is coagulated. In Holland and in 
Cheshire annatto is most commonly employed, while in other dis- 
tricts the marigold or the carrot, boiled in milk, are the usual colouring 
matters. 



MODE OF CURING THE CHEESE. 579 

The quantity of annatto employed is comparatively small — less than 
half an ounce to a cheese of 60 lbs. — but even this quantity is considered 
by many to be an injurious admixture. Hence a native of Cheshire 
prefers the uncoloured cheese, the annatto being added to such only as 
are intended for the London or other distant markets. 

14^. Size of the cheese. — From the same milk it is obvious that cheeses 
of different sizes, if treated in the same way, will at the end of a given 
number of months possess qualities in a considerable degree different. 
Hence, without supposing any inferiority, either in the milk or in the ge- 
neral mode of treatment, the size usually adopted for the cheeses of a 
particular district or dairy, may be the cause of a recognijzed inferiority 
in some quality which it is desirable that they should possess in a high 
degree. 

15'^. The method of curing has very much influence upon the after- 
qualities of the cheese. The care with which they are salted — the 
warmth of the place in which they are kept during the first two or three 
weeks — the temperature and closeness of the cheese-room in which they 
are afterwards preserved — the frequency of turning, of cleaning from 
mould, and of rubbing with butter — all these circumstances exercise a 
remarkable influence upon the after-qualities of the cheese. Indeed, in 
very many instances the high reputation of a particular dairy district or 
dairy farm is derived from some special attention to one or other or to all 
of the apparently minor points to which I have just adverted. 

In Tuscany, the cheeses, after being hung up for sometime at a proper 
distance from the fire, are put to ripen in an underground cool and damp 
cellar; and the celebrated French cheeses of Roquefort are supposed to 
owe much of the peculiar estimation in which they are held, to the cool 
and uniform temperature of the subterranean caverns in which the 
inliabitants of the village have long been accustomed to preserve them. 

In Rosshire it is said to be the custom with some proprietors to bury 
their cheeses under the sea sand at low water, and that the action of 
the sea- water in this situation renders them more juicy and of an exquisite 
flavour. 

16°. Ammoniacal cheese. — The influence of the mode of curing upon 
the (luality is shown very strikingly in the small ammoniacal cheeses of 
Brie, which are very much esteemed in Paris. They are soft unpressed 
cheeses, which are allowed to ripen in a room the temperature of which 
is kept between 60° and 70^^ F. till they begin to undergo the putrefac- 
tive fermentation and emit an ammoniacal odour. They are ge- 
nerally unctuous, and sometimes so small as not to weigh more than an 
ounce. 

A little consideration, indeed, will satisfy you, that b}'' varying the 
mode of curing, and especially the temperature at which they are kept, 
you may produce an almost endless diversity in the quality of the cheeses 
you bring into the market. 

17°. Inoculating cheese. — It is said that a cheese, possessed of no 
very striking taste of its own, may be inoculated with any flavour we 
approve of, by putting into it with a scoop a small portion of the cheese 
which we are desirous that it should be made to resemble. Of course 
this can apply only to cheeses otherwise of equal richness, for we could 
scarcely expect to give a single Gloucester the flavour of a Stilton, 
25 



580 AVERAGE QUANTITY OF CHEESE YIELDED. 

by merely putting into it a small portion of a rich and esteemed Stilton 
cheese. 

§ 22. Of the average quantity of cheese yielded by different varieties of 
milk^ and of the produce of a single cow. 
There appear to be very great differences in the proportions of cheese 
yielded by milk at different seasons and in different localities. 

In milk, of an average quality, there are contained from 4 to 5 per cent, 
of casein or dry cheesy matter (p. 534),which, if all extracted, would give — 
6 lbs. to 7 lbs. of skimmed milk cheese, or } from 100 lbs. of 
9 lbs. to 10 lbs. of entire milk cheese, ^ milk. 

This is very nearly the proportion actually obtained in some of the 
best dairy districts in the summer season. Thus — 

In Ayrshire — 10 lbs. of milk, or ? gave 1 lb. of whole milk 
1 imperial gallon, ^ cheese ; 

or 136 wine quarts gave 127J lbs. of cheese three months old.* 

In Gloucester — 7 lbs. of milk, or ) gave 1 lb. of double 
3i wine quarts, ^ Gloucester ; 

this is a much larger proportion, and is probably much above the average 
of the county. 

In Holstein, it is said that 100 lbs. of milk will give about — 

New skimmed milk cheese 6 lbs. 

Butter 3^ " 

Butter-milk 14 " 

Whey 76|" 



100 lbs. 

But this statement is so far indefinite that it affords us no means of 
judging how much curd is left in the butter-milk, nor how much water 
was present in the new cheese. Indeed, most of the statements on record 
are deficient in this respect, that the dryness of the cheese is not accu- 
rately expressed. 

In Cheshire, the average produce of a cow is reckoned at 360 lbs. of 
whole milk cheese, or about 1 lb. per day for the whole year. Taking 
8 wine quarts of milk as the average daily yield of a cow in that county, 
we have as the average produce of the milk the whole year through — 
1 lb. of cheese from 8 wine quarts, or 16 lbs. of milk. 

It is indeed undoubted, that the j'^^oportion of cheese varies very 
much with the season of the year and ivith the dryness of the loeather. 
Though, therefore, in summer 7 or 8 lbs. of milk may sometimes yield 
a pound of cheese, it is possible that as much as 20 lbs. of milk may at 
other seasons be required to give the same quantity. Thus in — 

South Holland, the summer produce of a cow is reckoned at about 200 
lbs. of skimmed milk cheese, and 80 lbs. of butter ; or in a week 10 lbs. 
of skimmed milk cheese, and 4 to 7 lbs. of butter. Of whole milk 
cheese some expect as much as 3 or A lbs. a day. 

* Mr. Alexander, of Southbar, informs me that the result of his experience with a dairy 
of 40 cows in the higher part of Ayrshire, near Muirkirk, is, that — 

90 imperial quarts of sweet milk give an Ayrshire stone of 24 lbs. of full milk cheese, 
while the same quantity of skim milk gives only 16 lbs. of skimmed milk cheese. That is 
very nearly — 

9 lbs. of new milk give 1 lb. of full milk cheese. 

14 lbs. of skim-milk give 1 lb. of skim-milk cheese (see p. 585). 



MILK SPIRIT AND MILK VINEGAR. 581 

In Switzerland, generally, a cow, giving 12 quarts of milk a day will, 
during the summer, yield a daily produce of 1^ lbs. of whole or full milk 
cheese — or 10| quarts of milk, about 21 lbs., will give a pound of cheese. 

In the high pastures of Scaria, again, in the same country, one cow 
will give for the 90 days of summer about 60 lbs. of skimmed-milk 
cheese and 40 lbs. of butter — or 11 ounces of cheese per day. 

It appears, therefore, as we should otherwise expect, that the average 
produce of cheese is affected by many circumstances — but that in this 
country 8 to 10 lbs. of good milk, in the summer season, will yield one 
pound of whole milk cheese. 

§ 23. Of the fermented liquor from milk, and of milk vinegar. 

Milk is capable of undergoing what is called the vinous fermentation, 
and of yielding an intoxicating liquor. The Tartars prepare such a 
liquor from mare's milk, to which the name of Arowmiss is given. When 
made from cow's milk it is called airen, and is less esteemed because 
generally of a weaker qualit3^ The Arabians and Turks prepare a si- 
milar liquor, which the former call lehan, and the latter yaourt. In the 
Orkney Islands, and in some parts of the north of Scotland and Ireland, 
butter-milk is sometimes kept till it undergoes the vinous fermentation, 
and acquires intoxicating qualities. 

It is the sugar contained in milk which, by the fermentation, is changed 
into alcohol. As mare's milk, like tliat of the ass, contains more sugar 
(p. 534) than that of the cow, it gives a stronger liquor, and is therefore 
naturally preferred by the Tartars. By distillation ardent spirits are ob- 
tained from koumiss, and when carefully made in close vessels, a pint of 
the liquor will yield half an ounce of spirit. The koumiss is prepared in 
the following manner : 

To the new milk, diluted with a sixth of its bulk of water, a quantity 
of rennet, or what is better, of sour koumiss, is added, and the whole is 
covered up in a warm place for 24 hours. It is then stirred or churned 
together till the curd and whey are intimately mixed, and is again left 
at rest for 24 hours. At the end of this time it is put into a tall vessel, 
and agitated till it becomes perfectly homogeneous. It has now an agree- 
able sourish taste, and in a cool place may be preserved for several 
months in close vessels. It is always shaken up before it is drunk. This 
liquor, from the cheese and butter it contains, is a nourishing as well as 
an exhilarating drink, and is not followed by the usual bad effects of in- 
toxicating liquors. It is even recommended as a wholesome article of 
diet in cases of dyspepsia or of general debility. 

Milk vinegar. — If the koumiss be kept in a warm place the spirit dis- 
appears and vinegar is formed. In some parts of Italy a milk vinegar 
of pleasant quality is prepared by ad4ing honey, sugar, spirit, and a lit- 
tle yeast to the boiled whey, and setting the mixture aside to ferment in 
a warm place. [II latte e i suoi prodotti, pp. 415 and 450.] 

§ 24. Of the composition of the saline constituents of milk 

When milk is boiled down to dryness, and the dry residue burned, a 

small quantity of ash remains behind. The proportion which the 

weight of this ash bears to that of the whole milk is variable — as the 

qualities of the milk itself are — so that 1000 lbs. will leave sometimes 



582 USE or milk in thb animal economy. 

only 2 lbs., at others as much as 7 lbs. of ash. This ash consists of a 
mixture of common salt and chloride of potassium (p. 188), with the 
phosphates of lime, magnesia, and iron. The relative proportions of 
these several substances yielded by 1000 lbs. of the milk of two dif- 
ferent cows, were as follows [Haidlen, Annal. der Chem. und Phar., 
xiv., p. 273] : 

I. II. 

Phosphate of lime 2-31 lbs. 3-44 lbs. 

Phosphate of magnesia . . . 0-42 *' 0-64 '• 

Phosphate of peroxide of iron . 0-07 " 0-07 " 

Chloride of potassium .... 1-44 " 1-83 '* 

Chloride of sodium 0-24 " 0-34 ♦* 

Free soda 0-42 " 0-45 " 

4-90 " 6-77 " 

It is probable that the phosphates and chlorides existed as such in the 
milk as it came from the cow, the free soda is believed to have been in 
combination with the casein, and to have held it in solution in the milk. 
You will recollect that the explanation I have given of the curdling of 
milk is, that the acid produced in, or added to, the milk, takes this soda 
from the casein, and renders it insoluble in water, and that in conse- 
quence it separates in the form of curd (see p. 566). 

§ 25. Purposes served by milk in the animal economy. 

Milk is the food provided for the young animal, at a period when it is 
unable to seek food for itself. It consists, as we have seen, of — 

1°. The casein or curd. — This being almost identical in constitution 
with the lean part or fibrin of the muscles serves to promote the growth 
of the flesh of the animal. 

2°. The fat or butter, which is mainly expended in supplying fat to 
those parts of the body in which fat is usually deposited. 

3°. The sugar, which is probably consumed by the lungs during re- 
spiration. ' 

4°. The saline matter, from which come the salts contained in the 
blood, and the earthy part of the bones of young and growing animals 
fed upon milk. 

These several purposes served by milk will come again under our 
consideration in the following lecture. 



NOTES. 
1°. On the churning of butter in the French chum. 
Mr. Burnett, of Gadgirth, has favoured me with the following infor- 
mation regarding the merits of the French churn mentioned in page 
555 :— 

" I see you make mention, in page 555 of your Lectures, of a churn 
lately introduced by Mr. Blacker from France. I got one of these from 
Mr. Blacker about two years ago, and have proved its merits to be very 
great. I use none else, and have been the means of distributing it over 



CHURNING IN THE FRENCH CHURN. 583 

different parts of England and Scotland. It is made of tin, of a barrel 
shape, and is placed in a trough of water, heated or otherwise, to convey 
the proper temperature to the cream. I have tried many experi- 
ments to ascertain the proper temperature for churning cream in 
this churn, and have found that 58° F. produces the best quality of but- 
ter in the shortest time — the time occupied being from ten to twenty 
minutes. At 60° it was often done in five to seven minutes, and although 
a little soft at first, produced butter of a good colour and quality — on no 
occasion was it ever white. I also tried 56° F. It took generally one 
hour, was harder, but no better in quality than that of 58°. 

" With regard to the quantity of butter from a given quantity of cream, 
I found that in July, when the cows were on good pasture, and occasion- 
ally house-fed on clover — 

16 quarts of cream produced . 12 lbs. 8 oz. 

24 do. do. do. . 16 lbs. 12 oz. 

30 do. do. do. . 20 lbs. 8 oz. 



Or, 70 quarts produced 49 lbs. 12 oz. 

When fed on cabbage — 

50 quarts of cream produced . . 32 lbs. 
Again — 

50 quarts of cream produced . . 32 lbs. 4 oz. 
60 do. do. do. . . 40 lbs. 

Or (lie whole six quarts of cream in July gave 4 lbs. of butter. 

" On churning the ivhole milk in this churn, 100 quarts of milk at 60° 
produced 8 lbs. of butter of excellent quality in one hour and a half — 8 
quarts of hot water were put into the churn according to the old system. 

" 100 quarts of milk from the same cows at 64° produced only 7 lbs. 
of butter of a soft and inferior quality, and took two hours to chum, 16 
quarts of hot water being put into the churn on this occasion. 

" The whole milk was sometimes churned in less than one hour, but 
from that to one hour and a half was the general time occupied, whereas 
three to four hours is the time occupied in churning in the comjnon chum. 

" To ascertain whether the whole milk or the cream produced the 
greatest quantity of butter in this churn, I took the milk of five cows 
(Ayrshire breed) for one week in July last, amounting to 508 quarts — 
the yield of butter was 36 lbs. 11 oz. I then took the same quantity of 
milk from the same cows for the same period of time, and let it stand for 
cream — the butter produced was 37 lbs. 4 oz. The food and other cir- 
cumstances were quite the same. 

*' To test the quality of my butter, I sent it last summer to a show at 
A3rr, and obtained the second premium both for fresh and salt ; the heat 
at which it was churned was 58°, and the time not exceeding half an 
hour." 

On these observations of Mr. Burnett, I must in fairness remark, that 
several other persons who have used this churn, have not reported by any 
means so favourably of its merits. Perhaps they have not known how 
to manage it so skilfully. 

2°. Quantity of milk and butter yielded by Ayrshire caws. 
Mr. Alexander, of Southbar, has furnished me with the following pro- 



584 COMPARATIVE PROFIT OF 

portions of cream and butter yielded by his dairy of 38 cows, at Well- 
wood, in the higher part of Ayrshire, near Muirkirk, during six several 
days in November and December, 1843 : — 

Cream Butter 

Date. in imp. galls. in pounds. 

November 1 ...... 16 43 J 

7 ...... 191 47| 

♦' 14 18J 43 

" 21 21 f 47 

" 29 18 39 

December 7 19 43^ 

In all 112^ galls, gave 263| 

or, seven quarts of cream in Novemher gave four pounds of butter. 

The cream appears from the table to have become gradually less rich, 
though the whole quantity did not diminish. 

Mr. Alexander remarks, that " the proportion of cream varies in his 
dairy from ;^th to y^^th of the bulk of the milk, and that the Guernsey or 
Highland, or any black or black-marked cow, gives more cream from the 
same quantity of milk." That is, they give a richer milk. 

This is a curious physiological fact, and is probably related to an ob- 
servation made in the fattening of these races, that the same quantity of 
food goes further in fattening a black or black-marked than a dun or white 
beast. I do not suppose. that any thing of this kind has been observed in the 
Durham breed — as white animals, of pure blood, are often great favour- 
ites with the breeders of Tees- Water stock. 

3°. Profit of making butter and cheese compared with that of 
selling the milk. 

For the following particulars I am also indebted to Mr. Alexander. 
The produce of cheese and butter is the average of his experience at 
Well wood, in Ayrshire. 

There are three ways in which the milk is usually disposed of. It is 
sold in the state of new milk, or it is made into full milk cheese, and the 
whey given to pigs — or it is made into butter, and the skim-milk sold, or 
made into cheese, or given to pigs. The profit of each of these three 
methods, at the Ayrshire prices, is as follows approximately : — 

s. d. 
a. — 90 quarts of new milk, at 2d« a quart, are sold for . 15 
b. — 90 quarts of new milk give 24 lbs. Of full milk cheese, 

which, at4|d., per lb. are sold for . . . .90 
The whey is worth, at least 6 

9 6 
c. — 90 quarts of milk, churned altogether, give 9 lbs. of butter, 

.at9d. 6 9 

90 quarts of butter-milk, at \A. per quart . . . .39 



10 6 
In the country, where the butter-milk cannot be sold, it is given to the 
pigs, and does not yield so large a return. 



MAKING BUTTER AND CHEESE. 685 

S. d. 

90 quarts of new milk give 18 quarts of creain, yielding 

9 lbs. of butter at 9d., as before . . . . .69 

18 quarts of butter-milk, at ^d. . . . . .09 

70 quarts of skim-milk, at ^d. 2 11 



10 5 

When the skim-milk cannot be sold, it may be given to the pigs, or 
it may be made into skim-milk cheese. In the latter case the profit is 
as follows : — 

8. d. 
e. — Butter and butter-milk, as before . . . . .76 
70 quarts of skim-milk give 16 lbs. of cheese, which, at 3d. 

per lb, 4 



Thus we have 90 quarts of milk — 



11 6 



s. 


d. 


15 





9 


6 


10 


6 


10 


5 


11 


6 



a — sold as new milk, worth .... 

6 — made into full-milk cheese .... 

c — made into butter and butter-milk, where the latter 
can be sold ...... 

d — made into butter and skim-milk, where the latter 
can be sold ...... 

e — made into butter and skim-milk cheese 

In the country, therefore, according to these calculations, the most pro- 
fitable way is to make butter and skim-milk cheese. The farmer is thus 
in a great measure independent of an adjoining population. The small 
quantity of butter-milk he thus obtains he will easily be able to dispose 
of, or otherwise to employ to advantage. 

According to Mr. Ayton, it is still more profitable to feed calves with 
the milk, but I find many people differ from him on this point. At all 
events, a good and ready market is required for the veal. 



LECTURE XXI. 

Of the feeding of animals, and the purposes served by their food.-^Substances of which the 
parts of animal bodies consist. — Whence do the animals derive these substances— are 
they all present in the food 7 — Use of the starch, gum, and sugar contained in vegetable 
food.— Functions of a full-grown animal. — Of the respiration of animals.— General origin 
and purposes served by the fat in carnivorous and herbivorous animals.— Of the digestive 
process in animals. — Purposes served by food and digestion. — The food sustains the full- 
grown animal. — Necessity of a mixed food. — It sustains and increases the fattening ani- 
mal. — Relative fatiening powers of different kinds of food. — How circumstances aflfect this 
fattening property.— Purposes served by food in the pregnant — in the young and growing 
animals, such as the calf— and in the milk cow.— Effect of different kinds of food on the 
quality of the milk.— Fattening of the cow as the milk lessens in quantity— Experimental, 
economical, and theoretical value of different kinds of food for these several purposes. — 
Circumstances which affect these values. — Soil, manure, form in which the food is given, 
ventilation, light, warmth, exercise, activity, salt and other condiments. 

Having in the preceding lectures considered the composition of the 
direct products of the soil — grains, roots, and grasses — and of the most 
important indirect products — milk, butter, and cheese — the only part of 
our subject which now remains to be discussed is the relative values of 
these several products in the feeding of animals. 

Under this head it will be necessary to enquire how far these values 
are affected by the age, the growth, the constitution, and race of the ani- 
mal — by the purposes for which it is fed — and by the circumstances 
under which it is placed while the food is administered to it. 

§ 1 . Of the substance of which the parts of animals consist. 

The bodies of animals consist of solid and fluid parts. 
1°. The solid parts are chiefly made up of the muscles, the fat, and 
the bones. 

a. The muscles, in their natural state, as I have already had occasion 
to mention (p. 444), consist in 100 parts of about — 

Dry matter 23 

Water 77 

100 
so that, to add 100 lbs. to the weight of an animal in the form of muscle, 
only 23 lbs. of solid matter require to be incorporated with its system. 

When the muscular or lean part of beef, mutton, &;c., is washed 
in a current of water for a length of time — the blood, to which the red 
colour is owing, and all the soluble substances, gradually disappear, and 
the muscle becomes perfectly white. In this state, with the exception 
of some fatty and other matters which still remain intermixed with it, the 
white mass forms what is known to chemists by the name of fibrin. 
This name is given to it because it forms the fibres which run along the 
muscles and constitute the greater portion of their substance. 

The following table exhibits the relative proportions of muscular fibre 
and other substances contained in the flesh of several different animals in 
its natural state, [Schlossberger, Annalen der Pharmacie, December, 
1842, p. 344] :— 



COMPOSITION OF RECENT MUSCLE. 687 



Calf. § ■« ^ -rf 

O 1°. 2°. g^ ^ S S O H 

Muscular fibre, vessels.nerves 
and cellular substance . . 17-5 150 16-2 16-8 18-0 17-0 16-5 12'0 U'l 

Soluble albumen and colour- 
ing matter of blood Uiema- 
tosin) 2-2 3-3 26 24 23 45 3-0 52 4*4 

Alcoholic extractjcontaining ) ^.^ j.j ^.^ ^.^ . ^ ^.q ^.^ j.q ^.g 
saline matter S f o.^ 1 

Watery extract, containing » ^.3 ^^ j.g q.q i ^ ^.^ ^.g 1-7 o-3 
saUne matter ) ^ ^ 

Phosphate of lime, with a lit- 
tle albumen* trace 01 trace trace 0-4 — 0*6 — 2-3 

Water and loss 775 79-7 78-2 783 76-9 76-0 77-3 80-1 805 

100 100 100 100 100 100 100 100 100 

The proportions in the above table are not to be regarded as constant ; 
they seem, however, to shew what we should otherwise expect, that the 
muscular part of fishes contains a less proportion of fibrin than that of 
land animals in general. 

When dried beef is burned it leaves about 4| per cent, of incombus- 
tible ash — or 100 lbs. of the muscle of a living animal in its natural 
state contain about one pound of saline or inorganic matter. 

Of this inorganic matter, it is of importance to know that about two- 
thirds consist ^ phosphate of lime. Thus to add 100 lbs. to the muscular 
part of a full grown animal, there must be incorporated with its substance 
about — 

Water 77 lbs. 

Fibrin, with a little fat . . 22 " 
Phosphate of lime ... f " 

Other saline matters . . 3" 

100 

6. The fat of animals consists, like the fat of butter, of a solid and 
fluid portion. The fluid fat is in great part squeezed out when the whole 
is submitted to powerful pressure. 

The fluid portion of the fat, called by chemists oleine, so far as it has 
yet been examined, appears to be identical in all animals. It is also the 
same thing exactly as the fluid part of olive oil, of the oil of alnionds, 
and of the oils of many other fruits. It exists in larger qiiantity in the 
fat of the pig than in that of the sheep, and hence pork fat is softer than 
beef or mutton suet. From lard it is now expressed on a great scale in 
the United States of America, for burning in lamps and for other uses. 
The manufacturers of stearine candles express it from beef and mutton 
fat, but chiefly for the purpose of obtaining the solid part in a harder 
state, that it may make a more beautiful and less fusible candle.^ The 
fluid oil of animal fats, however, is known to differ from the liquid part 
of butter (butter-oil) described in the preceding Lecture (p. 559), and 
from the fluid part of linseed and other similar oils which dry, and form 

* This phosphate of lime is over and above that which exists naturally in, and is insepar- 
able from, the muscular fibre itself and from the albumen. 

^5* 



58d or FAT, A>D OF AVHAT BONES CONSIST. 

a kind of varnish when exposed to ihe air. These latter facts are not 
without their importance, as we shall hereafter see. 

The solid part of the fat of animals is known to vary to a certain ex- 
tent among different races. Thus the solid fat of man is the same with 
that of the goose, and with that which exists in olive oil and in butter. 
To this the name of margarine is given. But the solid fat of the cow, 
the sheep, the horse, and the pig, differs from that of man, and is 
known by the name of stearine. 

The solid and fluid parts are mixed together in different proportions in 
the fat, not only of different animals, but of the same animal at differ- 
ent periods, and in different parts of its body.. Hence the greater hard- 
ness observed in the suet than in other portions of the fat of beef and mut- 
ton, and hence also the different quality and appearance of the fat of an 
ox according to the kind of food upon which it has been fed or fattened. 

c. The bones, like the muscles, consist of a combustible and an incom- 
bustible portion, but in the bones the inorganic or incombustible part is 
by much the greater. To the organic matter of bones the name of g-el- 
atine or glue is given, and it can be partly extracted from them by boil- 
ing. The proportion of gelatine which exists in bones varies with the 
kind of animal — with the part of the body from which the bone is taken 
— and very often with the age and state of health of the animal, and with 
the way in which it has been accustomed to be fed. It is greater in spongy 
bones, in the bones of young animals, and probably also in the bones of 
such as are in high condition. In perfectly dry bone it rarely exceeds 
from 35 to 40 per cent, of the whole weight. 

The incombustible portion consists for the most part of phosphate and 
carbonate of lime. The relative proportions of these two earthy com- 
pounds also vary with the kind of animal, with its age, its condition, its 
food, and its state of health. To form 100 lbs. of bone the animal will 
usually require to incorporate with its own substance about — 
35 pounds of gelatine, 
55 pounds of phosphate of lime, 
4 pounds of carbonate of lime, 
3 pounds of phosphate of magnesia, 
3 pounds of soda, potash, and common salt. 



100 
d. Hair, horn, and wool, are distinguished from the muscular parts of 
the animal body by the large proportion — about five per cent. — of sul- 
phur which they contain. They consist of a substance which in other 
respects closely resembles gluten and gelatine in its chemical composi- 
tion (page 445). When burned, they leave from one to two per cent, of 
ash, which in the case of a variety of human hair, which left 1*1 per cent, 
of ash, was fimnd by Van Laer to consist of- — 

' Per cent. 

Soluble chlorides and sulphates 0-51 

Oxide of iron 0-39 

Phosphate and sulphate of lime, phosphate of magnesia and silica . 0-20 

1-lG 
The inorganic matter contained in hair is therefore, generally speak- 



of ] 



or HAIK, HORN, AND WOOL, AND OF BLOOD. 589 

ing, the same in kind as that which exists in the muscular fibre and in 
the bone. It contains the same phosphate of lime and magnesia — the 
same sulphates and the same chlorides, among which latter common salt 
is the most abundant. The absolute quantity of ash or inorganic matter 
varies, as well as the relative proportions in which the several substances 
are mixed together in the different solid parts of the body, but the sub- 
stances themselves of which the inorganic matter is composed are nearly 
the same, whether they be obtained from the bones, from the muscles, or 
from the hair. 

2°. Of the fluid parts of the body, the blood is the most important, 
and by far the most abundant. The body of a full grown man, of mo- 
derate dimensions, contains about 12 lbs. of blood, [Lehmann, Physi- 
ologische Chemie, I., pp. 113 and 338,] that of a full grown ox, six 
times as heavy, cannot contain less than 70 or 80 lbs. Blood consists of 

about — 

Per cent. 

Water 80 

Organic matter 19 

Saline matter 1 

100 
The organic matter consists chiefly of fibrin, which, when the blood 
coagulates, forms the greater part of the clot — and o£ albumen, which re- 
mains dissolved in the serum or fluid part of clotted blood, but which, 
like the white of egg, runs together into insoluble clots when the serum 
is heated. 

The saline matter remains dissolved in the serum after the albumen 
has been separated by heating, and consists chiefly of phosphates, sul- 
phates, and chlorides — nearly the same compounds as exist in the soluble 
part of the ash left by the solid parts of the body. 

Besides this soluble saline matter which remains in the serum, a por- 
tion of phosphate of lime and a small quantity of phosphate of magnesia 
exist also in the fibrin and in the albumen of the blood. Thus in the dry 
state these substances contain respectively of the mixed phosphates — 

Albumen of ox blood . . . . 1*8 per cent. ? (gerzelius ) 
Fibrin of human blood .... 0-7 per cent. J ^ '' 

Thus the same saline and earthy compounds, which form so large a 
portion of the bones, are distributed every where in sensible proportion9 
throughout all the more important solids and fluids of the body 

§ 2. Whence does the body obtain these substances 1 Are they contained 

in the food ? 

Whence does the body derive all the substances of which its several 
p^res consist ? 

-ic'he answer to this question appears at first sight to be easy. They 
must be obtained from the food. But when the enquiry is further coii- 
sidered, a reply to it is not so readily given. 

It is true, indeed, that the organic part of the food contains carbon, 
hydrogen, oxygen, and nitrogen — the elements of which the organic parts 
of the body are composed. The m-organic matter also which exists in 



590 WHENCE THE FAT AND BONES OF ANIMALS. 

the food contains the Hme, the magnesia, the potash, the soda, the sul- 
phur, the phosphorus, and the iron, which exist in the inorganic parts of 
the animal body — so that the question seems already resolved. The 
body obtains from the food all the elements of which it consists, and 
if these be not present in the food, the body of the animal cannot be 
properly built up and supported. 

But to the chemist and physiologist the more important part of the 
question still remains. In what state do these elements enter into the 
body 1 Are the substances of which the food consists decomposed after 
they are taken into the stomach ? Are their parts first lorn asunder, and 
then re-united in a different way, so as to form the chemical compounds 
of which the muscles, bones, and blood consist ? Are the vital powers 
bound to labour, as it were, for the existence and support of the body ? 
Do they compound or build up out of their ultimate elements the various 
substances of which the body is composed — or do they obtain these sub- 
stances ready prepared from the vegetable food on which animals, in 
general, are fed ? The answer which recent chemical researches give to 
this second question forms one of the most beautiful contributions which 
have been made to animal physiology in our time. 

l'^. We have seen that the'flour of wheat and of our other cultivated 
grains consists in part of gluten, of albumen, or of casein. These sub- 
stances all contain nitrogen, and are identical in constitution with each 
other, and with the fibrin of which the muscles of animals chiefly con- 
sist.* The substance of the muscles exists ready formed, therefore, in the 
food which the animal eats. The labour of the stomach is in conse- 
quence restricted to that of merely selecting these substances from the 
food and dispatching them to the several parts of the body, where they 
are required. The plant compounds and prepares the materials of the 
muscles — the stomach only picks out the bricks, as it were, from the other 
building materials, and sends them forward to be placed where they 
happen to be wanted. 

2°. Again, we have seen that in all our crops, so far as they have 
been examined, there exists a sensible proportion of fatty or oily matter 
more or less analogous to the several kinds of fat which exist in the boJies 
of animals. In regard to this portion, therefore, of the body, the vege- 
table performs also the larger part of the labour. It builds up fatty sub- 
stances out of their elements — carbon, hydrogen, and nitrogen. These 
substances the stomach extracts from the food, and the body appropriates 
them, after they have been more or less slightly changed, in order to 
adapt them to their several purposes. There may possibly be other 
sources of fat, as we shall hereafter see, but the simplest, the most na- 
tural — and probably, where a sufficient supply exists, the only one had 
recourse to by the healthy animal — is the fat which is found, ready 
formed, in the vegetable food it eats. 

3°. Further, the bones, the muscles, and the blood, contain phosp^^^jLe 

* The chemical reader, who is aware of the exact state of our knowledge upon this sub- 
ject, will perceive that I speak here of the identity of these substances only in so far as the 
proportions of carbon, hydrogen, oxygen, and nitrogen are concerned. It is unnecessary to 
allude in this place to the different proportions of sulphur and phosphorus they are known 
to contain — as the more popular nature of this work will not permit me to discuss the re- 
fined, though singularly beautiful, physiological questions with which these differences are 
connected. 






tHE FUNCTION OF RESPIRATION. 591 

of lime, phosphate of magnesia, common salt, and other saline com- 
pounds. These same compounds exist, ready formed, in the vegetable 
food, associated generally with the gluten, the albumen, or the casein, 
it contains. The materials of the harder parts of the body, therefore— 
(the phosphates) as well as the inorganic saline substances which are 
found in the blood, and in the other fluids of the body — are all formed in 
or by the plant, or are by it extracted from the soil and incorporated with 
the food on which the animal is to live. 

Not only, therefore, do the mere elements of which the parts of the 
bodies of animals are formed, exist in the food — but they occur in it, put 
together and combined, nearly in the state in which they are wanted, in 
order to form the several solids and fluids of the body. The plant, in 
short, is the compounder of the raw materials of living bodies. The ani- 
mal uses up these raw materials — cutting them into shape when neces- 
sary, and fitting them to the several places into which they are intended 
to be built. 

This is a very simple, and yet a very beautiful view of one of the 
many forms of chemical connection which exist between the processes 
and purposes of animal and vegetable life. Nature seems to divide the 
burden of building up living bodies between the vegetable and the animal 
kingdoms — the lower appearing to exist and to labour only for the good 
of the higher race of beings. 

§ 3. Of the respiration of animals, and of the purposes served by the starch, 
gum, and sugar, contained in vegetable food. 

But, besides the gluten of plants and seeds, which supplies the mate- 
rials from which the muscular parts of animals are formed, the oil which 
is converted into the fat of animals, and the saline and earthy matters 
of plants which supply the salts of the blood and the earth of the bones — 
vegetable food in general contains a large proportion of starch, sugar, 
gum, and other substances which consist of carbon and the elements of 
water only (p. 111). "What purpose is served by this part of the food? 
Is it merely taken into the stomach and again rejected, or is it decom- 
posed and made to serve some vital purpose in the economy of the 
living animal ? From the fact that so large a part of all vegetable food 
consists of these substances, we might infer that they were destined to 
serve some important purpose in the animal economy. To the herbiv- 
orous animal they are, in fact, almost necessary for the support of a 
healthy life. 

In order to understand this fact, it will be necessary briefly to advert to 
the respiration of animals — the chemical changes produced by it, and 
the purposes it is supposed to serve in the animal economy. 

1°. Of the function of respiration. — All animals possessed of lungs al- 
ternately inhale and exhale the atmospheric air. They breathe, that is, 
or respire. The air they draw into their lungs, supposing it to be dry, 
consists by volume (pp. 32 and 148) very nearly of — 

Nitrogen . 79-16 

Oxygen 20-80 

Carbonic acid 0-04 

100 
95 



592 FAT SUPPORTS RESPIRATIOIV IN SOME, 

— ^the proportion of carbonic acid being very small. But as it is breathed 

out again it consists of about — 

Nitrogen 79'16 

Oxygen 16-84 to 12 

Carbonic acid 4-00 to 8 



100 
— the proportion of oxygen being considerably less, that of carbonic acid 
very much greater, than before. On an average the natural proportion 
of carbonic acid in the air is found to be increased 100 times after it is 
expelled by breathing from the lungs. 

Now carbonic acid consists, as we have previously seen, of carbon and 
oxygen. In breathing, therefore, the animal throws off into the air a 
quantity of carbon — in the form of carbonic acid — which varies at dif- 
ferent times, in different species of animals, and in different individuals of 
tlie same species. By a healthy man the quantity of carbon thus 
thrown off varies from 5 to 13 ounces, and by a cow or a horse from 3 to 
5 pounds, in 24 hours. All this carbon must be derived from the food. 
The animal eats, therefore, not merely to support or to add weight to its 
body, but to supply the carbon also which is wasted by respiration. 

2°. Hoiv the respiration is fed. — What part of the food supplies the 
waste caused by respiration ? How is the respiration fed ? 

In animals which live upon flesh — carnivorous animals — it is the fat 
of their food from which the carbon given off by their lungs is derived. 
It is only when the fat fails in quantity that the lean or mitscular part 
of the flesh they eat is decomposed for the purpose of supplying carbon 
to their lungs. 

In an animal to which no food is given for a time, the lungs are fed, 
60 to speak, from fat also. But in this case it is the living fat of the 
animal's own body. When digestion is fully performed and hunger is 
keenly experienced, the body begins to feed upon itself — the lungs still 
play, respiration continues for many days after food has ceased to be ad- 
ministered, but the carbon given off is derived from the substance of the 
body itself. The fat first disappears — escapes with the breath — and af- 
terwards the muscular part is attacked. Hence the emaciation which 
follows a prolonged abstinence from food. 

In animals which live upon vegetable food again — herbivorous ani- 
mals — it is the starch, gum, and sugar, of the food which supply the 
carbon for respiration. It is only when the food does not contain a suf- 
ficient supply of these compounds that the oil first, and then the gluten, 
are decomposed, and made to yield their carbon to the lungs. 

In man, who lives on both kinds of food, and in the domestic dog, and 
the pig, which also eat indifferently both animal and vegetable food, the 
carbon of respiration may be derived in part from the fat, and in part 
from the starch and sugar which they eat — according as they are chiefly 
supported by the one or by the other kind of food. 

It may be asked how we know that such are the parts of the food, to 
which the duty of supplying the demands of the lungs is especially com- 
mitted. There are several considerations which lend force to this opin- 
ion. Of these I will draw your attention to one or two. 

a. Why is the fat rather than the lean part of the food 9f carnivorous 



STARCH AND SUGAR IN OTHER RACES. 593 

animals devoted to the service of the lungs, and why do starving ani- 
mals lose their fat first ? Because the chemical decomposition by which 
carbon can be derived from the fat is simpler and more eeisily eiTected 
than that by which it can be obtained from muscular fibre. By combi- 
nation with oxygen, fat can be converted into carbonic acid and water 
only, of which the former will pass off by the lungs and the latter in the 
urine. The muscular fibre, on the other hand, contains much nitrogen 
(p. 444), and, if deprived of its carbon for the uses of respiration, must 
undergo very complicated decompositions, and form a series of com- 
pounds, the use of which, in the animal economy, it is not easy to perceive. 

Besides, in producing the carbonic acid of the lan^rs from the fat of the 
animal food or of the living body, there is less waste of material. Fat 
consists wholly of the three elements, carbon, hydrogen, and oxygen. 
These all disappear entirely in the form of carbonic acid and water — both 
of which are used up. Muscle, on the other hand, besides nitrogen, con- 
tains a constant proportion of sulphur and phosphorus. If the muscle, 
then, be decomposed for the purpose of supplying carbon to the lungs, 
not only the large quantity of nitrogen, but the sulphate and phosphorus 
also, would go to waste, and would pass off in the urine. In nature, 
however, such waste is rarely seen to take place ; and, therefore, as a 
general rule, the respiration will be supported by the muscular fibre only 
when other kinds of food are deficient. 

b. But in the stomachs of herbivorous animals, why are the starch and 
sugar especially appropriated to the use of the lungs ? The food of ani- 
mals which live upon vegetable substances contains fat as well as starch 
— why then is the starch in this case dissipated by the process of respira- 
tion, while the fat is applied as it is supposed to another use ? The 
answer to this question is both beautiful and satisfactory. 

Starch, gum, and sugar, consist of carbon and water only, and we can 
conceive them in their passage through the body to be actually separated 
into these two substances — in which case the carbon has only to combine 
with oxygen and form carbonic acid, to be ready to pass off by the lungs. 
Here, therefore, only one chemical combination is required — the union 
of carbon with oxygen. It is the simplest way in which we can con- 
ceive carbon to be supplied for the use, or for the purposes of the lungs.* 

But it is otherwise with fat. Though nearly all kinds of fat consist en- 
tirely of carbon, hydrogen, and oxygen-«-yet they cannot be supposed to 
consist only of carbon and water. They contain much more hydrogen than 
is necessary to form water with the oxygen which is present in them. If, 
then, the carbon of these fats be separated, this excess of hydrogen will 
also be set free, and if the former be made to combine with oxygen to 
form carbonic acid^ the latter must also combine with hydrogen to form 
water. Thus two chemical changes must go on simultaneously, for 
which more oxygen will be required, and which involve more labour in 
the system than when the carbon alone is to be combined with oxygen. 
It is natural, therefore, that where both starch and oil are present to- 
gether, the former should be first converted to the uses of the lungs, the 
latter only when the supply of starch or sugar has been exhausted. 

* The chemical reader will understand that lam here only giving a popular view of the 
JiTzcd result of the several changes through which the carbon no doubt passes before it 
escapes in the form of carbonic acid. 



594 PURPOSES SERVED BY RESPlRATIOI<f . 

There appears, therefore, to be a beautiful adaptation to the wants and 
convenience of animals in the large proportion of starch, gum, and sugar, 
which the more abundant varieties of vegetable food contains. In obtaining 
carbon from these, the least possible labour, so to speak, is imposed upon 
the digestive organs of the herbivorous races. The starch and sugar 
abound because much carbon is required, while fatty matter or oil is 
present in smaller quantity, because comparatively little of this is neces- 
sary to the perfoiTnance of the usual healthy functions of the animal 
body. And it is another adaptation of the living body to the circum- 
stances in which it may be placed, that when starch or sugar cannot be 
obtained, the oil of the food is consumed for the supply of carbon to the 
lungs — and failing this also, the gluten and albumen of the vegetable food 
or the muscular fibre of the animal food, or even of the living animal it- 
self. 

3'^. Purposes served by respiration. — But for what purpose essential to 
life do animals respire ? If the starch and sugar be so necessary to feed 
the respiration — the breathing itself must be of vital importance to the 
living animal. 

Some doubts still exist upon this point. It is generally believed, 
however, that carbon is consumed or given off from the lungs for the pur- 
pose of sustaining the heat of the living body. When starch, or sugar, 
or gum, are burned in the open air, they are changed into carbonic acid 
and water, and at the same time produce much heat. It is supposed that 
in the body the same change — the conversion of starch and sugar into 
carbonic acid and water — taking place, heat must in like manner be pro- 
duced. A slow combustion, in short, is supposed to be going on in the 
interior of the animal — the heat of the body being greater, in proportion 
to the quantity of carbonic acid given off from the lungs. In favour of 
this view many strong reasons have been advanced, but there are also 
objections against it of considerable weight, which cannot as yet be satis- 
factorily removed. 

Were we to adopt this opinion in regard to the main purpose served by 
respiration as the true one, it would afford a very distinct reason for the 
large amount of starch existing in all our cultivated crops. Respiration, 
according to this view, is necessary to supply heat to the animal, and 
this respiration is most simply and easily fed by the starch contained in 
the vegetable food. The life and labours of the plant again minister to 
the life and labours of the animal. 

§ 4. Of the origin and the purposes served by the fat of animals. 

1°. The immediate origin or source of the fat of animals depends upon 
the kind of food with which the animal is fed. Carnivorous animals 
obtain or extract it ready formed from the flesh they eat — herbivorous 
animals from the vegetable food on which they live. 

It has only been lately shown that the corn, hay, roots, and herbage, 
on which cattle are fed, contain a sufficient quantity of oily matter ready 
formed to supply all the fat which accumulates in their bodies — or which, 
by the milk cow, is yielded in the form of butter. Before the different 
kinds of food had been analyzed, with the view of determining the quan- 
tity of oil and fat they severally contain, it was supposed that the fat of 
animals was derived almost solely from the starch and sugar or gnm, of 



ORIGIN OF THE FAT OF ANIMALS. 595 

Which so large a proportion of vegetable food consists. This opinion 
however, has given way before the advance of analytical research! 
Animals fatten quickest upon Indian corn, or oil cake, or oil mixed with 
Chopped straw, or upon oily seeds and nuts— or, as in the case of poultry 
on a mixture of meal or suet— because these kinds of food contain a We 
proportion of fatty matter ready formed which the animal can easily ex- 
own su°b ^ *^*^^^ chemical change can convert into a portion of its 

The conversion of starch or sugar into fet in the animal body implies 
a cheniical change of a less simple nature— one which seems to impose 
upon the vital principle a greater amount of labour than is implied in the 
simple appropriation of the fat which exists ready formed in the food. If 
then, there be in the food as much fat as is necessary to supply all that 
tlie animal appropriates to itself, and if it is observed to lay on or appro- 
priate more when the food is richer in fatty oils, we are led to believe 
that the natural purpose served by the oil in the vegetable food is to supply 
the fat of the animal body. In other words, the vegetable ministers to the 
animal and lessens its labour by preparing beforehand the materials out 

^ u "'^,^"i™al IS to build up the fatty parts of its body. 

±{ut though this is the general source of the fat of animals, circum- 
stances may occur in which the only vegetable food which the animal can 
procure does not contain a sufficient proportion of fat to supply all the 
wants of Its body-or to enable it to perform the several natural functions 

M 1 T/"^ 'VV^^J- ^?"' '^^ ^' ^ ^^"^ o^ f^^' ^"d it has been shown 
(Milne Edwards) that, when fed upon pure sugar, the bee is capable of 
formmg wax from its food. When fed upon such sugar, it not only lays 
up a store of honey, but it continues to build its cells of wax. Now the 
starch of the food is readily changed into sugar. It may be so changed 
m the stomach of man and of other animals. That power which the bee 
possesses they also may in ca^es of emergency be able to exercise 
Where a sufficient supply of oil for the necessary uses of the animal is 
not contained m the food it eats, it may form an additional portion from 
the starch or sugar in which its food abounds. 

According to the present state of our knowledge, therefore, the most 
probable opinion m regard to the origin of the fat of animals seems to be 
expressed in these two proposition. 

a. That the fat of animals is contained ready formed, and is usually 
derived from the vegetable or other food on which they live— and that 
when the food abounds largely in fat, the animal lays it more quickly 
and abundantly upon its own body. 

\i'^^^* ^^^" ^^® ^*^°^ ^^^® "°^ contain a sufficient proportion of fat to 
3Qable the animal comfortably to perform the various functions of its 
30dy, It has the power to form an additional quantity from the starch or 
sugar It eats— but that it will not readily fatten or lay on large additions 
3f fat upon Its body when fed upon farinaceous, saccharine, or other food 
.H which oil is not naturally contained.* 

• For the sake of the chemical reader I may be permitted here to show by what kind of 
:?TJ/i f A^^^rol^^^^ ^u of animals in general may be derived from the starch or sugar 
it their food ; and 2°, how the peculiar kinds of fat contained in the body of any given ani- 
»al may be formed from the peculiar kinds of fat contained in its food. 

l'^. How fat may be formed from starch or sugar.— These two substances, as we have 
ikeariy seen, may be represented by carbon and water only— > <« vv« uave 



CHANGES OF OX FAT INTO HUMAN FAT. 596 

oo The purposes served by the fat.---ln all healthy animals which 
take a S^Suantity of eicercisi to maintain them m a healthy con- 

S.rcH, cons.tin,"of 1% ^^^^ H ci Si" Si". 

Cam sugar, cons^Btmg of 12 +,. ^^j.^^'^^fX j^uman bidy, is represented (p. 

4 of starch — r/« Hss 05 

1 of margarine - C37 H36 us. 

Difference = Cu H4 035 

This difference is eju^/oi-/,5f/5FTr^l'/j- 9 of oxygen 
11 C02 + 4 HO + 9 O 




water, 

may be used up - . 

verted into fat. ch^tanres may be changed into the fat of animals was first 

That in some such way 1^?^® substances may d« ^ s ^^^^ ^^^t ^l^at m 

insisted upon and explained by L>eb,g^^^^^^^^ j,i„ds of food But 

cases of emergency tans reaUy formed '" "Vctit was not known that vegetable substances 
when Liebig put forth h.s ^ley o" this subject,^t wy not^K^^^^^ |^ ^ The ne- 

naturally contained so large a PPP^'^'?"; ^Ln^n^f r^Hn the body itself, therefore, is not now 
SsUy for the con..tant Production or for^^tu^n of fat in ^e^^^^^^ ^ ^^^ 

so apparent, and the so^^^^f "-.S""' ^fS alUhe fat ready formed which the animal re- 
that, whUe the vegetable ^o^ t^woWy supph^^^^^^ y^ ^^ ^^^^ of the eel- 

quires, yet that a conyersioi^^of a certain pa^^^^^^^^ me ^,^| ^^^^s^^ ^^^ ^^^^ 

hiiar fibre of the food, into fat ma/ taKe P'a«« ^^ tl^is opinion applies only to 

m the food. , .. jj^j p^rt of butler, of olive oil, and of the goose, 

pSS Slfe^/o^y' SrA°ar rT^Se^' Cri,iSan.a.nce .heae .inds of fa. aeen. 
remarkably fitted for the food of man. qtparine lloon this man lives much 

l>a r.lkl/S.o'£ ^^urfitm^'.^'.e^fSoCr.y. HhU .a, u.e p.ac» afer 
the foUowing manner :- = C74 H72 Oio 

2 of margarine — C?4 Hg9 O7 

lofstearine ~._1_:_L 

Recent researches, however have f^^'f.j" ^=^,^^"sVft" and must be speedily converted into 
It er^rai! 7.1 S rtrrrpoS;?ri.'e" evo,u,io„ oF .he 3 of carbon <Ca > 

ra'S„°e'!;?rbr,i:;bSeS°1b°/rv\r^f'S.e'";«vloua caL 

be changed mto the UquH fat of the Mow. p„ai„„n of elaine-the liquid fat of 

thfoS Sr^'dTelr^SmpSe'd Sffof tx^r oif presents a considerable difTerence. 

Thus— T-l :„« . . . = C47 H42 06 

K?oii :::::•• =c37H3306 

f »>,•. ^^if.rJ^rf^cfom we* are u'^ble as yet precisely to explain. By 
What becomes of thw difference, >''"^"7.Y=,„*iive rise to a litUe more fat. 
the intervention of a httle oxygen it might "^^^^JJ^ J^^^^'^^^^ the existence of this Iran*: 

d. The cow and calf t??ether however, uusiraie^ , ^^^ composition of 

forming power of the animal body. We ^re "nacquaimea, as ye , ^^^^^ ^^^ ^^^ 

[neve?al l^^ds of fat wWch occur in v^^^^ i„ itsownteUow, 

can form the two kinds of fat--the steanne ana me eu. butter-oil~which are found m its 
'^L^' %lfX%luXTcS thV'e tr KrrS'into those which ita own body, aa 



PURPOSES SERVED BY THE FAT. 597 

dltion, the principal purposes served by the fat are simple and the same. 
It lubricates the joints — covers and protects the internal viscera — keeps 
the muscles separate, and enables them to play freely among each other 
— makes the hair and skin soft and flexible, — and, by filling up hollows, 
contributes to the roundness and plumpness of the parts, and defends the 
extremities of the bones from external injury. When exercise is taken, 
a portion of the fat of the body appears to be more or less changed and 
removed, and is afterwards found in the perspiration, or in the dung. It 
is to make up for this natural waste that all animals, even when the fat 
of their body undergoes no increase, require a certain supply to be daily 
given to them in their food. 

The accumulation of fat in animals seems to be an effort of nature to 
lay in a store of food in time of plenty, which may be made available in 
the performance of the usual functions of the animal when a time of 
scarcity comes. If the food contain too little oil to lubricate the joints 
and to supply the natural waste of this kind of matter, then the store of 
fat which has been accumulated in time of plenty is drawn upon, a por- 
tion of it is worked up, so to speak, and the fat of the body diminishes in 
quantity. We have seen also that the respiration of carnivorous animals 
is supported at the expense of the fat which they eat — and that the lean- 
ness which attends upon starvation is owing to the fat of the living body 
beingconsumed in supplying the carbon given off from the lungs. Another 
purpose, therefore, for which animals seem to be invested with the power 
of laying on fat, is, that a store of food for the purposes of respiration 
may be carried about in the body itself, to meet any unusual demand 
which the food may not be able wholly to supply. 

§ 5. Of the natural waste of the parts of the body in a full grown animal. 

We have seen that, if the food of the animal be unable to supply the 
carbon given off from the lungs, and the fat which the movements of the 
limbs require, the parts of the body themselves are laid under contribu- 
tion in order to supply these substances. Thus, when the food is stinted, 
the body necessarily undergoes a waste from this cause. 

But this is not a constant waste. It is prevented by the use of a larger 
quantity of food. The parts of the body, however, do undergo a con- 
stant and natural waste, to make up for which is one of the main pur- 
poses served by the food. 

It has been ascertained by physiologists, that all the parts of the body 
undergo a slow and insensible process of renewal. The hair and the nails 
we can see to be constantly renewed. They grow, or are thrust out- 
wards. But the muscles and even the bones are by little and little re- 
well as that of itB mother, requires. And, lastly, man by eating the fat of the calf can re- 
convert it into margarine and those other fatty substances which are found in the various 
parts of his body. Substances which can thus so frequently and so readily be changed, the 
one into the other, must be very cloeely connected, and the mode in which their mutual 
transformations are effected will, no doubt, prove to be simple when these are rightly \m- 
derstood. 

The chemical reader will understand that it is for the sake of simplicity only that I have 
in this note compared together the entire fats stearine, margarine, &c., instead of the fatty 
acids only which they are known to contain. 

The reader will consult with much advantage and satisfaction upon this subject, a work 
upon Chemical Physiology, by Professor Mulder, of Utrechi, (Procve eener Algenwene Phy- 
siolo gische Scheikunde, p. 260, et seq.) of which I am happy to say that a translation from 
the Dutch is now In progress by my assistant, Mr. Fromberg, and will speedily be published 
by the Messrs. Blackwood. 



598 FOOD REQUISITE FOR THE NATURAL WASTE. 

moved inwardly and rejected in the excretions — the place of that whichi 
is removed being supplied by new portions of matter derived from the* 
food. 

This removal, though unfelt by us, goes on so rapidly that in a space 
of time, which varies from one to five years, the whole body of the ani- 
mal is renewed. There does not remain, it is said, in any of our bodies, 
a single particle of the same matter which formed their substance three 
or five years ago. It is just as if we were to take a single old brick every 
day out of the corner of a house, and put in a new one — the form and 
dimensions of the house would remain unaltered, and yet in the coursf 
of a few years its walls would be entirely renewed. 

In full grown animals, some parts of the body are renewed more ra 
pidly than others — the muscles, for example, more frequently and rapidly 
than the bones and the brain. In young animals, again, the whole bodyl 
is oftener renewed than in such as are advanced in years, but all the 
parts of all animals are believed to be more or less quickly removed and 
replaced. 

The new materials which are conveyed to the different parts of the 
body are derived directly from the food. The fibrin of the muscles is 
replaced from the gluten which the food contains — the fat from its oil — 
and the earthy matter of the bones and the salts of the blood, from the 
phosphates and saline substances which are naturally present in it. On 
the other hand, those parts which are extracted from the muscles and 
bones, and carried off in the excretions, are decomposed during their re- 
moval. New chemical compounds are produced from them, which are 
found in the urine and dung of the animal, and which give to these ex- 
cretions their richness and value in the manuring of the soil. 

§ 6. Of the hind and quantity of food necessary to make wpfor the natural 
waste in the body of a full grown animal. 

The substances which constantly disappear from the body in conse- 
quence of the natural waste above described, are of three kinds — the^&nn 
and other analogous organic compounds, which form the muscles and the 
cartilage of the bones — the earthy phosphates (of lime and magnesia), 
which form so large a proportion of the bones, and exist in small quan- 
tity in the muscles also— and the soluble saline substances, which abound 
in the blood and in the other fluids of the living animal. In the solid and 
liquid excretions, a larger quantity of each of these three classes of com- 
pounds is carried out of the body. How much of each must be contained 
in the daily food of a full-grown animal in order that it may be kept in 
its actual condition? 

1°. Quantity of fibrin or other analogous compo7inds (albumen or 
casein) which the daily food must contain, — The most accurate experi- 
ments that have yet been made upon this subject (Lecanu) appear to 
show that a full grown man rejects in his urine alone about half an ounce 
of nitrogen (230 grs.) every 24 hours. This quantity of nitrogen is con- 
tained in about three ounces of dry muscular fibre, which must, therefore, 
every day be decomposed or removed in order to yield it. 

But if the body is kept in condition, this quantity of fibrin must be 
daily restored again by the food. Now, to supply three ounces of dry 
fibrin, there must be eaten about — 



IN THE BODY OF A FULL-GROWN ANIMAL. 599 

30 ounces of wheaten flour ; or 
45 '* of wheaten bread ; or 
14 " of fresh beef or mutton ; or 
12 " of pease or bean meal ; or 
4 '* of cheese ;* 
Or, if we live wholly upon potatoes or milk, we must eat no less than 
six or seven pounds of the former daily, or drink three or four imperial 
pints of the latter — 'if Ave would restore to the body as much of the sub- 
stance of its muscles and cartilage as is daily removed from it by the 
urine. 

But the urine is not the only channel through which nitrogen is given 
oflf from the animal body. A considerable, though, of course, a variable 
proportion is found in the solid excretions or dung, which has also been 
derived from the substance of the body itself. A small quantity of ni- 
trogen is believed to be given off from the lungs also in breathing, and 
from the skin in the perspiration, which nitrogen must have been either 
directly or indirectly derived from the food. And, lastly, of the fibrin or 
other food containing nitrogen which may be introduced into the stomach, 
a portion must pass the mouths of the absorbent vessels as it descends 
through the intestines and thus escape with the dung, without having 
performed its part in the ordinary nourishment of the body. 
J It is impossible to make any correct estimate of the 'amount of nitrogen 
' which escapes from the animal in the several ways just noticed — in the 
soUd excretions from the lungs and from the skin — or of the quantity of 
food which is necessary to supply its place. If we suppose the loss 
through all these sources taken together to be equal to one-half or two- 
thirds of that which is found in the urine, then the whole quantity of dry 
I fibrin which the food ought to contain would amount to four and a half or 
five ounces in the day. To supply this, we must eat of bread, beef, 
cheese, potatoes, or milk, one half more than the quantities already 
specified. 

No experiments have hitherto oeen published from which we can de- 
termine the average quantity of nitrogen rejected in the excretions of the 
\ horse, the cow, or the sheep, and, consequently, the amount of waste 
j which takes place in ordinary circumstances in the muscles and cartilage 
[ of these animals. If we suppose that in the horse or cow it is in direct 
proportion to their weights, compared with that of a full grown man— or 
j five times greater than in a man — then the loss of dry fibrin would 
amount to 20 or 25 ounces in the 24 hours. To supply this, the animal 
must eat the following quantities of one or other of the kinds of food here 
. mentioned : — 

120 lbs. of turnips. 17 lbs. of clover hay. 

I 115 '* of wheat straw. 12 " of pea straw. 

75 •' of carrots. 12 " of barley. 

\ 67 ♦' of potatoes. 10 •♦ of oats. 

20 " of meadow hay. 5 " of beans. f 

' Or instead of the whole quantity of any one of these, a half or quarter or 
, any other proportion of each may be taken, and the animal will pro- 

' " Supposing the wheaten flour to contain 10 per cent, of gluten, and the cheese one half 
its weight of dry curd (see also pp. 506 and 531.) 
T These numbers are calculated from the table given In p. 531. 
95* 



600 A MIXED FOOD NECESSARY TO ANI»IALS. 

bably be found to thrive better on the mixture than if fed upon any one 
of these kinds of food alone. 

2°. Quantity of fixed saline matter and of earthy phosphates which 
the food ought to contain. — A full grown animal rejects in its dung, its 
urine, and its perspiration, as much saline and earthy matter as its 
food contains. If its body is merely maintained in its existing condition, 
only that which is removed from it by the daily waste is restored to it by 
the' daily food. Thus whatever quantity of saline and earthy matter is 
present in the food, an equal quantity is found in the excretions of the 
living animal. 

But how much of that which is found in the excretions has actually 
formed part of the living body, and been removed from it in consequence 
of the natural waste ? This we have no means as yet of determining. 
It must be considerable, but it varies with many circumstances, and the 
experiments which have hitherto been made and published do not enable 
us to say how much the average waste really is, and how much of the 
several more common kinds of food ought to be consumed by a full 
grown animaU in order to supply it with the necessary daily proportion 
of saline and eartliy substances. 

The benefits so often derived from the use of salt in the feeding of 
stock show how a judicious admixture of saline matter w^ith the food 
may render its othfflr constituents more available than they would other- 
wise be, to the support and increase of the animal body. 

§ 7. The health of the animal can he sustained only hy a mixed food. 

From what I have already stated, you see that the vegetable food eaten 
by a full grown animal for the purpose of keeping up its condition should 
contain — 

1°. Starch or sugar, to supply the carbon given off in respiration. 

2°. Fat or fatty oil, to supply the fatty matter which exists more or 
less abundantly in the bodies of all animals. 

3°. Gluten or fibrin, to make up for the natural waste of the muscles 
and cartilage. 

4°. Earthy phosphates, to supply what is removed from the bones of 
the full grown animal by the daily waste ; and — 

5°. Saline substances — sulphates and chlorides — to replace what is 
daily rejected in the excretions. 

Hence the food upon which any animal can be fed with the hope of 
maintaining it in a healthy state must be a mixed food. Starch, or sugEu: 
alone, or pure fibrin or gelatine alone, will not sustain the animal body, 
because these substances do not contain what is necessary to build up all 
its parts, or to supply what is daily given off during respiration and in 
the excretions. The skilful feeder, therefore, will not attempt to main- 
tain his stock on any kind of food which does not contain a sufficient 
supply of every one of the kinds of matter which the body requires. 

Two other points he will also attend to. First, he will occasionally 
change the kind of food, or will vary the proportions in which he gives 
the different kinds of fodder to his feeding stock. This practice is founded 
on the fact that, although every crop he raises contains a certain propor- 
tion of all the substances which the animal requires, yet some contain 
one of these in larger quantity than others do, and by an occasional 



ADDITIONAL FOOD REQUIRED FOR FATTENING. 601 

change or variation he may hope more fully to supply to the animal the 
necessary quantity of each. 

Second, he will adapt the kind and quantity of food to the age of the 
animal, and to the other purposes for which it is fed. This rule depends 
partly upon the same fact, that different vegetables contain the several 
kinds of necessary food in different proportions, but in a great degree also 
upon the further fact, that the animal requires these substances in differ- 
ent proportions, according to its age and to the special purpose for which 
it is fed. Let me direct your attention to this latter fact a littler more 
at length. 

§ 8. O/* the kind and quantity of additional food required by the 
fattening animal. 

In the animal which is increasing in size or in weight, the food has a 
double function to perform. It must sustain and it must increase the 
body. To increase the body, an additional quantity of food must be con- 
sumed, but the kind or nature of this additional food will depend upon 
the kind of increase which the animal is making or is intended to make. 

One of the important objects of the stock farmer is to make his full 
grown animals lay on fat, so that they may as quickly as possible, and 
at the least cost, be made ready for the butcher. To effect this object, 
he adjusts the kind and quantity of the food he gives, to the practical ob- 
ject he wishes to attain. 

We have already seen reason to believe, that the natural and imme- 
diate source of the fat of animals is in the oily matter which the food 
contains. If we wish only, or chiefly, to lay on fat, therefore, we 
ought to give some kind of food which contains a larger proportion of 
fatty matter than that upon which the animal has been accustomed to 
live. This is what the practical man has actually learned to do. To 
his sheep and oxen he gives oil-cake or linseed oil mixed with chopped 
straw, to his dogs cracklings,* to his geese and turkeys Indian corn, 
which contains much oil, and to his poultrj"^ beef or mutton suet. 

Many experiments are yet wanting to determine with accuracy the 
proportion of fat contained in all the different kinds of food usually con- 
sumed by animals. Nearly all we yet know upon this subject is ex- 
hibited in the tabular view of their composition to which I have already 
directed your attention (p. 531.) 

One thing, however, of considerable practical value has been recently 
ascertained — that the oily matter of seeds exists chiefly near their outer 
surface, — in or immediately under the skin or husk. This fact is shown 
in the case of wheat, by tJie following results of the examination of two 
varieties of this grain, one grown near Durham, the other in France. 
The result as to the French grain is given by Dumas : — 

PER CENTAQB OF FATTY OIL. 

English. Frenclu 

Fine flour ... 1-5 1-4 

Pollard .... 2-4 4-8 

Boxings .... 3-6 — 

Bran 3-3 5-2 

" Cracklings are the skinny parts of the suet from which the tallow has been for the most 
part squeezed out by the tallow chandlers. Might cattle not be fattened upon cracklings 
crushed and mixed with their other food? Might not some cAecp varieties of oU also be 
mixed with (heir food for the purpose of fattening. 



602 FATTY MATTER IN THE HUSKS OP SEEDS* 

This fact of the existence of more fat in the husk than in tlie inner 
part of the grain, explains what often seems inexplicable to the practical 
man — why bran, namely, which appears to contain little or no nourish- 
ing substance, should yet fatten pigs and other full grown animals, when 
given to them in sufficient quantity along with their other food. It also 
explains why rics dust should be found to fatten stock,* though the 
cleaned and prepared rice contains but little oil, and is believed, there- 
fore, to be unfitted for laying on fat upon animals with any degree of 
rapidity. No doubt ihe dust from pearl-barley and from oats, as well as 
the husk of these grains, might be economically employed by the stock 
feeder where they can readily be obtained. 

§ 9. Kind and quantity of additional food required hy a grovnng 

animal. 

The young and growing animal requires also that its food should be 
adjusted to its peculiar wants. In infancy the muscles and bones in- 
crease rapidly in size when the food is of a proper kind. This food, 
therefore, should contain a large supply of the phosphates, from Avhich. 
bone is formed, and of gluten or fibrin, by which the muscles are en- 
larged. Some kinds of fodder contain a larger proportion of these phos- 
phates. Such are corn seeds in general, and the red clover among grass- 
es. Some again contain more of the materials of muscles. Such are 
beans and peas among our usually cultivated seeds, and tares and other 
leguminous plants among our green crops. " 

Hence the skilful feeder or rearer of stock can often select with judg- 
ment that kind of food which will specially supply that which the ani- 
mal, on account, of its age or rapid growth, specially requires — or which, 
with a view to some special object, he wishes his animal specially to lay 
on. Does he admire the fine bone of the Ayrshire breed? — he will try 
to stint it while young of that kind of food in which the phosphates 
.abound. Does he wish to strengthen his stock, and to enlarge their 
bones ?— he will supply the phosphates liberally while the animal is 
rapidly growing. 

An interesting application of these principles is seen in the mode of 
feeding calves adopted in different districts. Where they are to be reared 
for fattening stock, to be sold to the butcher at two or three years old, 
they are well fed with good and abundant food from the first, that they 
may grow rapidly, attain a great size, and carry much flesh. If starved 
and stunted while young, they often fatten rapidly when put at last upon 
a generoiLS diet, but they never attain to their full natural size and weight. 

When they are reared for breeding stock or for milkers, similar care is 
taken of them in the best dairy countries from the first, though in some 
the allowance of milk is stinted, and substitutes for milk are early given 
to the young anmials. 

But it is in rearing calves for the butcher that the greatest skill in 
feeding is displayed, where long practice has made the farmers expert in 
this branch of husbandry. To the man who has a calf and a milk cow, 
the principal question is, how can I, in the locality in which I am placed, 
make the most money of my calf and my milk ? Had I better give 
my calf a little of the milk, and sell the remainder in the form of new 

* Rice dust is very good food for fattening pigs, makes excellent pork, and is very profit^ 
able when given along with whey. 



FEEDING OF YOUNG CALVES. 603 

milk — or had I better make butter and give the skimmed milk to my 
calves— or will the veal, if I give my calf all the milk, pay me a bet- 
ter price in the end ? The result of many trials has shown, that in some 
districts the high price obtained for well fed veal gives a greater profit 
than can be derived from the milk in any other way. 

While the calf is very young— during the first two or three weeks 

its bones and muscles chiefly grow. It requires the materials of these, 
therefore, more than fat, and hence half the milk it gets, at first, may be 
skimmed, and a little bean meal may be mixed with it to add more of 
the casein or curd out of which the muscles are to be formed. The cos- 
tive effect of the bean meal must be guarded against by occasional me- 
dicine, if required. 

In the next stage, more fat is necessary, and in the third week at 
latest, fall milk, with all its cream, should be given, and more milk than 
the mother supplies if the calf requires it. Or, instead of the cream, a 
less costly kind of fat may be used. Oil-cake, finely crushed, or lin- 
seed meal, may supply at a cheap rate the fat which, in the form of 
cream, sells for much money. And, instead of the additional milk, bean 
meal in larger quantity may be tried, and if cautiously and skilfully used, 
the best effects on the size of the calf and the firmness of the veal may 
be anticipated. 

In the third or fattening stage, the custom is, with the same quantity 
of milk, to give double its natural quantity of cream — that is, to supply 
in this way the fat which the animal is wished chiefly to lay on. This 
cream may either be mixed directly with the mother's milk, or, what is 
better, the afterings of several cows may be given to the calf along 
with its food. For the expensive cream there might no doubt be sub- 
stituted many cheaper kinds of fat which the young animal might be 
expected to appropriate as readily as it does the fat of the milk. Lin- 
seed meal is given with economy. Might not vegetable oils and even 
animal fats be made up into emulsions which the calf would readily 
swallow, and which would increase his weight at an equally low cost ? 
A fat pease-soup has been found to keep a cow long in milk ; might it 
not be made profitable also to a fattening calf? 

The selection of articles of food which will specially increase the size 
of the bones in the growing animal, by supplying a large quantity 
of the phosphates, is at present limited in a considerable degree. The 
grain of wheat, barley, and oats is the source from which these phos- 
phates are most certainly and most abundantly supplied to the animals 
that feed upon them. But in many cases corn is too expensive a food, 
and those kinds of corn which contain the largest proportion of the phos- 
phates supply only a comparatively small quantity in a given time to the 
growing animal. "Why should not bone-dust or hone-meal be introduced 
as an article of general food for growing animals '/ There is no reason 
to believe that animals would dislike it — none that they would be unable 
to digest it. With this kind of food at our command, we might hope to 
minister directly to the weak limbs of our growing stock, and at pleasure 
to provide the spare-boned animal with the materials out of which a 
limb of great strength might be built up. 

Chemical analysis comes further to our aid in pointing out the kind 
of food we ought to give for the purpose of increasing this or that part 
26 



604 FOOD REQUIRED DURING PREGNANCY. 

of tne animal body. Thus in regard to the same growth of bone, it ap- 
pears that, while linseed and other oil cakes are mainly used with the 
view of adding to the fat, some varieties are more fitted at the same time 
to minister to the growth of bone than others are. Thus, four varieties 
of oil-cake examined in my laboratory, contained respectively of earthy 
phosphates and of other inorganic matter in 100 lbs. the following quan- 
tities :— 

PBR CENTA6K OF 





Earthy phosphates . 


Other inorganic matter. 


British linseed cake 


. . 2-86 


2-86 


Dutch . do. 


. . 2-70 


2-54 


Poppy cake . . 


. . 5-22 


1-24 


Dodder cake . . 


. . 6-67 


3-37 



The numbers in the first column, opposite to poppy and dodder cake, 
ehow that these varieties of oil-cake contained a much larger proportion 
of the phosphates than the others did, and consequently that an equal 
weight of them would yield to growing stock more of those substances 
which are specially required to build up their increasing bones. 

§ 10. Kind and quantity of additional food required by a 
pregnant animal. 

The food of the pregnant animal must sustain the full-grown mother, 
and must add at the same time to the substance of her unborn young. 
The quantity of food which is necessary to sustain the mother — if herself 
full-grown, which is often far from being the case — varies with many 
circumstances. 

It is said that in the stall an ox or a cow will eat one-fifth of its weight 
of turnips in a day, or one-fiftieth of dry food, such as hay and straw. 
With this allowance of food the animal would probably increase in 
weight in some degree, — but according to Riedesel one-sixtieth of its 
weight of dry hay is necessary merely to sustain it. From what we 
have already seen of the composition of the different grasses, it is obvi- 
ous that the quantity required will be much affected by the kind of hay 
with which the animal is fed. 

To nourish the young calf in the womb of its mother, an additional 
quantity of food must be given, and this quantity must be increased as 
die state of pregnancy advances. And though the kind of additional 
food which is given must readily supply the materials of the growing 
bones and muscles of the fcstus, yet it must contain also a larger quan- 
tity of starch or sugar also than the mother in her ordinary state would 
require. This is owing to the circumstance that the mother must now 
breathe for two animals, for herself and her young. The quantity of 
blood is increased, more oxygen is taken in by the lungs, and more carbon 
is given off" in the form of carbonic acid. To supply this carbon, more 
of farinaceous or saccharine food must be eaten from the time when 
pregnancy takes place, and it must increase as the young animal en- 
larges in size. 

Except in the way of feeding the mother, in all respects well, I am 
not aware that any experiments have been made with the view of spe- 
cially affecting the condition of the future calf by the kind of food given 
to the mother. A certain proportion of bone and muscle no doubt must 



FOOD REQUIRED BY A COW IN MILK. 605 

be supplied to the young animal by the food given to the mother, or the 
bones and muscles of the mother herself will be laid under contribution to 
supply it — but it does not appear impossible to aflfect the size of the bone 
by the quantity of phosphates which are given in the food, or the growth 
and development of the muscles by that of the gluten, fibrin, or casein 
with which the mother is fed. Might not an addition of hone-meal to the 
food of the pregnant cow give a calf of larger bone ? Would not bean- 
meal or skim-milk add to the size of its muscles ? 

§ 11. Kind and quantity of additional food required by a 
milking animal. 

After the young animal is born, the mother has still to feed it with her 
milk. And as the calf grows rapidly, the food it requires increases daily 
with its bulk, and the demands upon the mother therefore every day be- 
come greater. At this period, therefore, the cow must obtain larger sup- 
plies of food to sustain herself and to produce a sufficient quantity of 
milk for her calf than at any other period. If these adequate supplies 
are not given, a portion is daily taken from her own substance — her body 
becomes leaner, and her limbs more feeble, while her young also is 
stinted and puny in its growth. 

By-and-bye, however, the calf begins to pick up food for itself. It 
begins to live partly upon vegetables. The mother is in consequence 
relieved .of a part of her burden — her udders are less drawn upon — the 
quantity of milk secreted becomes less — she begins again to lay muscle 
and fat upon herself — her udders at length become dry, and she slowly 
recovers her original plump condition. She has, indeed, at this period a 
tendency to fatten if the same supply of food is continued to her, and 
in many districts it is customary to feed her off at this time for the 
butcher. 

What I have already said of the artifices by which the food given to 
the cow may possibly be made to affect the bodily character of the future 
calf, applies equally to the means of more or less effectually promoting 
the growth of the young animul while it is fed solely upon milk. The 
kind of food given to the mother may make the milk richer in curd, 
which will promote the growth of muscle — or richer in phosphates, by 
which the enlargement of the bones of the calf will be assisted. Scarcely 
any two samples of milk, indeed, are found, upon analysis, to contain 
the same proportion of phosphates and of other saline substances, and 
there is little reason to doubt that if an unusual quantity of these be given 
in the food of the mother, an unusual quantity will be found also in the 
milk she produces. 

For the production of milk the mother requires an adequate additional 
supply of all the substances which we have seen to be necessary to the 
support of the unborn foetus — of the starch as well as of the gluten and 
saline substances of the food. But it is interesting to mark the very dif- 
ferent purposes to which the additional supply of starch in her food is 
now applied. 

The pregnant mother requires this starch to supply the carbon given 
off more abundantly during her increased respiration. She breathes, as 
I have already said, for her young and for herself, and therefore gives 
off more carbon from her lungs. 



606 USES op MILK IN THE ECONOMY OP NATtTRE. 



But when the young animal is born it breathes for itself. It must, 
therefore, be supplied with that kind of food which seems specially in- 
tended to meet the wants of respiration. 

The additional starch eaten by the mother, therefore, instead of being 
breathed away in her own lungs, is conveyed in the form of sugar into 
the food of the young animal. It is changed into the sugar of the milk, 
and the natural function of this sugar is to supply the carbon which the 
young animal gives off when it begins to breathe for itself. 

It is not difficult to understand the kind of process by which the 
starch of the mother's food is converted into the sugar of her milk. If to 

2 of starch = 24C + 20H + 20O, 
vre add 4 of water = 4H -f 40, • 



4' 

«, 1! 



we have 24C + 24H + 240, which is the formula for 

milk sugar. In passing through the digestive organs of the cow, there- 
fore, the elements of the 2 of starch require only to be combined with 
those of 4 of water to be converted into the sugar of milk. 

But though it is not difficult to understand in what way this change 
may be effected, yet it is exceedingly interesting to find that such a 
chemical change as this should he made to commence at a certain special 
epoch with a mew to a certain special end. 

' Milk is a perfect food for a growing animal, containing the curd which 
is to form the muscles, the butter which is to supply the fat, the phos- 
phates which are to build up the bones, and the sugar which is to feed 
the respiration. Nothing is wanting in it. The mother selects all the 
ingredients of this perfect food from among the useless substances which 
are mingled in her own stomach with the food she eats — she changes 
these ingredients chemically in such a degree as to present them to the 
young animal in a state in which it can most easily and with least labour 
employ them for sustaining its body — and all this she begins to do at a 
given and appointed moment of time. How beautiful, how wonderful, 
how kindly provident is all this ! 



But apart from its natural use in the economy of nature, milk may be 
regarded as an article of manufacture — an important article of agricul- 
tural husbandry. As a mere producer of milk for other purposes than 
the feeding of calves, the cow will be differently fed according to the pur- 
pose for which her milk is intended to be employed, or the form in which 
it is to be carried to market. 

a. The town dairyman^ who sells his new milk to daily customers, 
requires quantity rather than quality. He gives his cattle, therefore, 
succulent food in which water abounds — green grass — forced rapidly for- 
ward by irrigation or otherwise — green clover, young rye, brewers* 
grains, or hay tea.* In this way, without "the actual addition of water, 
he can make his milk thin, and increase its bulk. 

h. Those, again, who desire much rich cream, or who grow milk for 

' A mixed hay tea and pease soup, which is excellent for making cows give milk, is pre>v 
pared by putting hay into a pot in alternate layers, sprinkling between each a handful of 
pease-meal, adding water and bringing to a boil. 



TO PRODUCE MILK FOR CHEESE OR BUTTER. 607 

the manufacture of butter, pay less attention to the bulk of the milk 
itself than to that of the cream, they can collect from its surface. The 
proportion of butter is increased by the use of food which contains much 
fatty matter — of any of those kinds of food, indeed, by which an ox can 
be made rapidly to lay on fat. Oil-cake has by some been objected to 
as likely to give a taste to the milk, but it may be safely used in small 
quantity, and gives an abundant and good flavoured cream. 

c. In cheese countries, again, it is the curd that is chiefly in request. 
No doubt the value of a cheese depends much upon the proportion of 
butter it contains diffused throughout its substance, but the weight of 
cheese produced upon a farm depends mainly upon the quantity of curd 
which the milk of the dairy yields. Where skim-milk cheese is made, 
the weight of produce obtained depends almost solely upon the richness 
of the milk in curdy matter. Clovers, vetches, and pea straw abound in 
casein or vegetable curd, and thus give a rich and productive milk to the 
cheese maker, while bean-meal and pease-meal, in so far as they can be 
given to the cow with safety, may with advantage be employed to pro- 
duce the same effect. As every thing which tends to lay on fat on the 
animal is likely also to increase the proportion of butter in its milk, so 
every thing which promotes the growth of muscle will also add to the 
richness of the milk in curd or cheese. 

§ 12. Influence of size, condition, warmth, exercise, and light, on the 
quantity of food necessary to make up for the natural waste. 

But the quantity of food of any kind which an animal will require is 
affected by many circumstances. Thus — 

1°. The size and condition of the animal will regulate very much the 
quantity of food which is necessary to sustain it. The larger the mus- 
cles and bones the greater will be the daily waste, and the greater the 
quantity, therefore, of the food necessary to replace it. If an animal re- 
quire a 50th or a 60th of its weight of dry food daily, of course his size 
and weight will regulate almost entirely the quantity of food he ought to 
eat. 

A knowledge of this circumstance is occasionally of economical value 
to the stock feeder or dairy farmer, and will modify very much the line 
of conduct he may be inclined to adopt as the most profitable. 

A large animal requires more food to keep it in its actual condition- 
to make up, that is, for the natural waste. If you wish to convert much 
produce into much rich dung, therefore, keep large animals. They will 
convert a large quantity of vegetable matter into manure without adding 
any thing to their own substance. If one-fiftieth of its weight of dry 
food be necessary to sustain it, then an animal of 100 stones weight will 
convert two stones of hay daily into dung. Whatever it eats beyond the 
two stones, will go to the increase of its weight. 

But a small animal, of 50 stones, requires only one stone a day to sus- 
tain its body, or converts one stone wholly into dung. Whatever it eats 
beyond this quantity, therefore, will go to the production of increased 
beef and bone. Hence, if I have a given quantity of vegetable produce, 
[ ought to be able to manufacture more beef from it by the use of small 
cattle than of large, provided my large and small stock are equally pure 
in breed, are equally quiet, and are as kindly feeders. 



608 INFLUENCE OP EXERCISE AND WARMTH* 

The same reasoning applies to dairy cows of different breeds. If I 
give two stones of hay to a smail Shetland cow, she may not convert 
more than one of them into dung, the other she may consume for the 
production of milk. But if I give the same quantity to a cow of double 
the size, nearly tlie whole two stones may be converted into dung — may 
be employed in sustaining the animal — and if she yield any milk at all, 
it will be poor and thin. 

This reasoning accounts for the fact which has been long observed, 
that small breeds of cattle give the richest milk, and that such as the 
small Orkney breed yield the largest produce of butter and cheese from 
the same quantity of food. They waste less of their food in sustaining 
their own bodies. Lean, spare cows also require less to sustain them ; 
and hence the skin-and-bone appearance of the best milkers among the 
Ayrshire and Alderney breeds. 

2°. The quantity of exercise which an animal takes, or of fatigue it 
is made to undergo, requires a proportionate adjustment in the quantity 
of food. The more it is exercised the more frequently it breathes, the 
more carbon it throws off from its lungs, the more starch or sugar con- 
sequently its food must contain. If more is not given to it, the fat or 
other parts of the body will be drawn upon, and the animal will become 
leaner? 

Again, the natural waste of the muscles and bones is said to be caused 
by, or at least to be in proportion to, the degree of motion to which the 
several parts of the body are subjected. Take more exercise, therefore, 
move one or more limbs oftener than usual, and a larger part of the sub- 
stance of these limbs will be decomposed, removed, and rejected in the 
excretions. Hence the reason why hard work requires good food, and 
why the strength of all animals is diminished, if they be subjected to 
great fatigue and are not in an equal degree supplied with nourishing 
food, by which the wasting parts of the body may be again built up. 

3°. The degree of warmth in which the animal is kept, or the tem- 
perature of the atmosphere in which it lives, affects also the quantity of 
food which the animal requires to eat. The heat of the animal is inse- 
parably connected with its respiration. The more frequently it breathes, 
the warmer it becomes, and the more carbon it throws off from its lungs. 
It is believed, indeed, by many, that the main purpose of respiration is to 
keep up the heat of the body, and that this heat is produced very much 
in the same way as in a common fire, by a slow combustion of that car- 
bon which escapes in the form of carbonic acid from the lungs. Place a 
man in a cold situation, and he will either starve or he will adopt some 
means of warming himself. He will probably take exercise, and by this 
means cause himself to breathe quicker. But to do this for a length of 
time, he must be supplied with more food. For not only does he give 
off more carbon from his lungs, but the exercise he takes causes a greater 
natural waste also of the substance of his body. 

So it is with all animals. The greater the difference between the tem- 
perature of the body and that of the atmosphere in which they live, the 
more food they require to " feed the lamp of life" — to keep them warm, 
that is, and to supply the natural waste. Hence the importance of plan- 
tations as a shelter from cold winds to grazing stock — of open sheds to 
protect fattening stock from the nightly dews and colds — and even of 



EFFECT OF ABSENCE OF LIGHT. 609 

closer covering to quiet and gentle breeds of cattle or sheep, which feed 
without restlessness and quickly fatten. 

A proper attention to the warmth of his cattle or sheep, therefore, is of 
great practical consequence to the feeder of stock. By keeping them 
warm he diminishes the quantity of food which is necessary to sustain 
them, and leaves a larger proportion for the production of beef or 
mutton. 

Various experiments have been lately published, which confirm the 
opinions above deduced from theoretical considerations. Of these I shall 
only mention one by Mr. Childers, in which 20 sheep were folded in 
the open field, and 20 of nearly equal weight were placed under a shed 
in a yard. Both lots were fed for three months — January, February, 
and March — upon turnips, as many as they chose to eat, half a pound 
of linseed cake, and half a pint of barley eacli sheep per day, with a 
little hay and salt. The sheep in the field consumed the same quantity 
^ of food, all the barley and oil-cake, and about 19 lbs. of turnips per day, 
from first to last, and increased on the whole 36 stones 8 lbs. Those 
under the shed consumed at first as much food as the others, but after 
the third week they eat 2 lbs. of turnips each less in the day, and in the 
ninth week, again 2 lbs. less, or only 15 lbs. a day. Of the linseed-cake 
they also eat about one-third less than the other lot, and yet they in- 
creased in weight 56 stones 6 lbs., or 20 stones more than the others. 

Thus the cold and exercise in the field caused the one lot to convert 
more of their food into dung, the other more of it into mutton. 

But why did the sheltered sheep also consume less food ? Why did 
they not eat the rest of the food offered them, and convert it also into 
mutton? Because the stomach of an animal will not do more than a 
certain limited amount of work in the way of digesting, after the wants 
of the body are fully supplied. When circumstances cause the sustain- 
ing quantity of food to increase, the digestive powers are stimulated into 
unusual activity, and though plenty of food be placed before the. animal 
it may be unable to consume and digest more than is barely sufficient to 
keep it in condition. If the sustaining portion be lessened, by placing 
the animal in new circumstances, more food may be digested than is ab- 
solutely necessary to supply the daily waste — that is to say, the animal 
may increase in weight. But the unusual stimulus being removed, it 
may not now be inclined, perhaps not be able, to digest so large a quan- 
tity as it did before when that large quantity was necessary to sustain its 
body — that is to say, that while it increases in weight it will also con- 
sume less food. 

4°. The absence of tight has also a material influence upon the effects 
of food in increasing the size of animals. Whatever excites attention in 
an animal, awakens, disturbs, or makes it restless, appears to increase 
the natural waste, and to diminish the effect of food in rapidl^^ enlarging 
the body. The rapidity with which fowls are fattened in the dark is 
well known to rearers of poultry.* In India, the habit prevails of sew- 
ing up the eyelids of the wild hog-deer, the spotted deer, and other wild 

* It is astonishing with what rapidity fowls (dorkinga) increase when well fed, kept in con- 
fined cribs, and in a darkened room. Fed on a mixture of 4 lbs. of oatmeal, 1 lb. of suet, 
and i lb. of sugar, with milk for drink five or sixtimes a day in summer, a dorking will add 
to its weight 2 lbs. in a week, sometimes IJ lbs. in four days. A young turkey will lay on 3 
j>3. a week, under the same treatment. 



610 



VENTILATION AND CLEANLINESS. 



animals when netted in the jungles, with the view of taming and speedily 
fattening them. The absence of light indeed, however produced, seems 
to soothe and quiet all animals, to dispose them to rest, to make less food 
necessary, and to induce them to store up more of what they eat in the 
form of fat and muscle. 

An experiment made by Mr. Morton, on the feeding of sheep, shows 
the effect at once of shelter, of quiet, and of the absence of light upon 
the quantity of food eaten and of mutton produced from it. 

Five sheep, of nearly equal weights, were fed each with a pound of 
oats a-day and as much turnips as they chose to eat. One was fed in 
the open air, two in an open shed — one of them being confined in a crib — 
two more were fed in a close shed in the dark — and one of these also was 
confined in a crib, so as to lessen as much as possible the quantity of ex- 
ercise it should take. The increase of live weight in each of the five, 
and the quantity of turnips they respectively consumed, appear in the 
following table : — 











Increase 


LIVE WEIGHT. 






for each 




' ^ 


Increase. 


Turnips 


100 lbs. of 


Nov. 18. 


March 9. 




eaten. 


turnips. 


lbs. 


lbs. 


lbs. 


lbs. 


lbs. 


108 


131-7 


23-7 


1912 


1-2 


102 


129-8 


27-8 


1394 


2-0 • 


108 


130-2 


22-2 


1238 


1-8 


104 


132-4 


28-4 


886 


31 


111 


131-3 


20-3 


886 


2-4 



Unsheltered 

In open sheds .... 
Do., but confined in cribs 
In a close shed in the dark 
Do,, but confined in cribs 

From this table it appears, as we should have expected — 

a. That much less — one-third less — turnips was eaten by the animal 
which was sheltered by the open shed, than by that which was without 

^• shelter, while in live weight it gained four pounds more. 

b. That in the dark the quantity of turnips eaten was one-half less, 
and the increase of weight a little greater still. 

c. But that when confined in cribs — though the food eaten might be a 
little less — the increase in weight was not so great. The animal, in 
fact, was fretful and restless in confinement, and whatever produces this 
effect upon an animal prevents or retards its fattening. 

d. That the most profitable return of mutton from the food consumed, 
is when the animal is kept under shelter and in the dark. 

Such a mode of keeping animals, however, must not be entered upon 
hastily or without due consideration. The habits of the breed must be 
taken into account, the effect of the confinement upon their health must 
be frequently attended to, and, above all, the ready admission of fresh air 
and a good ventilation must not be forgotten. By a neglect of the pro- 
per precautions, unfortunate results have frequently been obtained and a 
sound pradTice brought into disrepute. 

5°. Ventilation and cleanliness indeed are important helps to economy 
in the feeding of all animals. Shelter and warmth will do harm, if free 
and pure air is not admitted to the fattening stock. The same is true of 
cleanliness, so favourable to the health of all animals. The cleaner 
their houses and skins are kept, the more they thrive under any given 
form of treatment in other respects. 



EFFECT OF THE SOURING OF FOOD. 611 

§ 13. Influence of the form or state in which the food is given rni the 

quantity required by an animal. 
The state in which the food is given to his stock has often an important 
injfluence upon the profits of the feeder. Thus — 

1°. The souring of the food, in some cases, makes its use more econo- 
mical. Arthur Young details several series of experiments on the fat- 
tening of pigs, in which bean meal was given mixed with water in the 
sweet state, and after it liad been allowed to stand several days to sour. 
In every case in which it was given sour, the pork obtained gave a profit 
upon the price of the meal, while in every case in which the same meal 
was given sweet and in equal quantity, the price obtained for the pork 
was less than that which was paid for the meal. 

Upon sour food, indeed, pigs are universally observed to fatten best. 
In Holstein, it is customary to collect waste green herbage of every kind, 
and to let it sour in water. It then fattens pigs which would scarcely 
thrive on it before. During this souring of vegetable matter in water, it 
is lactic acid — the acid of milk — which is chiefly produced. This acid, 
therefore, would appear to favour the increase of size in the pig, and to 
this cause may be owing the profitable use of sour whey in feeding this 
kind of stock in cheese-making districts. 

I have been told by some cow-feeders who use brewers' grains, that 
the dry cows, when fattening oflT, relish the grains inost when slightly 
sour, and fatten most quickly upon them. From others, however, I 
have obtained a contrary opinion, and have been assured that fattening 
stock of all kinds like the grains best, and thrive best upon them, when 
perfectly sweet and fresh. It is a matter of doubt, therefore, whether or 
not the souring of food generally, of all kinds and for all kinds of stock, 
can be safely tried or recommended. 

2°, The boiling or steaming of dry food, and even of potatoes and tur- 
nips, is recommended by many as an economical practice. I beheve 
that the general result of the numerous experiments which have been 
made upon this subject in various parts of the country is in favour of. 
this opinion in so far as regards fattening and growing stock. It seems a 
more doubtful practice in the case of horses which are intended for heavy 
and especially for fast work — though even for these animals the use of 
steamed food is beginning to be adopted by some of the most extensive 
coach contractors. [Stephens' Book of the Farm.] 

3°. It is a curious fact not less worthy of the attention of the chemist 
than it is of the practical man, that the age of the food singularly aflfects 
its value in the nourishment of animals. Thus new oats are not con- 
sidered fit for hunters before the months of February or March. They 
affect the heels and limbs with something like grease, and make the 
horse unfit for fast work. Nor is it merely water whicli the grain loses 
by the five or six months' keeping — for if it be dried in the kiln it is still 
unfit for use, from its stimulating in an extraordinary degree the action 
of the kidneys. Some chemical change takes place in the interior of the 
oat which has not yet been investigated. 

The potato, on the other hand, by keeping, loses much of its nutritive 
value, even before it has begun to sprout — and every feeder knows that 
turnips which have shot into flower, add much less than before to tlie 
weight of his fattening stock. 
26* 



612 INFLUENCE OF SOIL AND CULTURE ON THE 

§ 14. Influence of soil and culture on the nutritive value of agricultural 

produce. 

I have on several former occasions, (pages 500 to 528), directed your 
attention to the remarkable influence which soil, culture, and climate 
have upon the chemical composition of the different corn and green crops 
usually raised for food. Every such change of composition alters also 
the nutritive value of any given crop. If the wheat or barley be richer 
in gluten, it will build up more muscle — if it abound more in starch, a 
smaller weight of it will supply the carbon of respiration — if it be richer 
in fatty matter, it will round off the edges of the bones, and fill up the in- 
equalities in an animal's body more quickly with fat. Such differences 
as these I have already shown you do really exist among samples of the 
same kind of grain grown upon soils either of different quality, or of the 
same quality when differently cultivated or manured. 

But this different culture or manuring affects the relative proportions 
of the several kinds of inorganic matter also — the phosphates and other 
saline substances — which are known to exist necessarily in all vegetable 
productions. In illustration of this, I would direct your attention to the 
following analyses — made in my laboratory by Mr. Fromberg — of the 
ash of two samples of the same kind of turnip (red topped yellow) 
raised by Lord Blantyre, on the same field, the one with guano alone, 
the other with farm-yard dung alone. The quantity of ash left by the 
two varieties of turnip was 0*68 and 0*7 per cent, respectively^ and this 
ash was composed as follows : — 

Composition of the ash of turnips raised with guano, and with farm-yard dung. 

GUANO. DUNG. 

/ 

Interii 
Chloi'ide of Potassium 
Sulphate of Potash 
Carbonate of Potash . 
Phosphate of Potash . 

^ Lime . 

Magnesia 

Alumina 

Carbonate of Lime 

Alumina 

Oxide of Manganese . 
Silica 



Interior. 


Exterior. 


Interior. 


Exterior. 


556 


503 


540 


10-71 


30-85 


37 04 


3120 


35-47 


11-38 


903 


3674 


17-63 


3093 


1017 


551 


3-65 


4-55 


4-49 


1-58 


202 


034 


1-62 


2-63 


3-13 


4-87 


9.94 


0-92 


2-76 


9-52 


9-72 


11-56 


14-82 


509 


2-79 


0-94 


0-46 


3-21 


590 


2-60 


5.33 


1-65 


343 


— 


3-04 



97-95 9916 9908 99-02 

The most striking difference between the two varieties of ash is in the 
proportion of phosphates they respectively contain. The ash of the 
guano turnips contained from 25 to 30 per cent, of phosphates, that of 
the dung turnips only from 9 to 11 per cent. This could not fail to 
make an important difference in their relative values for the feeding of 
stock whose bones are growing, and which require, therefore, a larger 
supply of phosphates in their food. 

The phosphates of lime and magnesia form, as we know, one of the 
valuable constituents of guano, but we could scarcely have inferred that 
this manure would have caused so much larger a proportion of these 
phosphates to enter into the constituents of the turnips raised with them. 



NUTRITIVE VALUE OF AGRICULTURAL PRODUCE. 



613 



It is not unlikely that turnips, raised from bones, will also abound more 
largely in phosphates than turnips raised from dung or rape dust, and 
may therefore be better fitted for growing stock. 

§ 15. Can we correctly estimate the relative feeding properties of different 
kinds of produce under all circumstances. 

Since the several nutritive effects of different kinds of food are de- 
pendent upon so many circumstances — upon the state of the animal 
itself— the purpose for which it is fed — the mode in which it is housed 
and protected — the form aod period at which it is given — can it be pos- 
sible to classify them in an order which will indicate their relative feed- 
ing values in all cases and for all purposes ? This is obviously impos- 
sible. We may easily arrange them in the order of their relative values 
in reference to some one of the several purposes for which food is given. 
We may shew in as many different tables the order of their relative 
values in laying on fat— in increasing the muscles— or in promoting the 
growth of bone ; but we cannot arrange theoretically, nor can experi- 
ment ever practically classify, all our common vegetable productions in 
one invariable order which shall truly represent their relative values in 
reference to each of these three different points : — 

1°. Experimental values. — This, however, practical writers have often 
attempted to do. Making their experiments in different circumstances, 
with different varieties of the same produce, upon different kinds of 
stock, or upon animals fed for different purposes, they have obtained re- 
sults of the most diversified kind, and have classified the several kinds of 
fodder in the most unlike order. I select a few of these results for the sake 
of illustration. Taking 10 lbs. of meadow hay as a standard, — then, to 
produce an equal nutritive effect, the different quantities of each of the 
other kinds of fodder represented by the numbers in the following table 
ought to be used— according to the several authors whose names are 
given. 

Experimental quantities of fodder which must he used to produce an 
equal nutritive effect, according to — 

Meadow hay 
Aftermath hay 
Clover hay . 
Green clover in flow 

er and lucerne 
Lvicerne hay 
Wheat straw 
Barley straw 
Oat straw . 
Pea straw . 
Potatoes 
Old potatoes 
Carrots . . 
Turnips . . 
Wheat . . 
Barley . . 
Oats ... 
From an inspection of this table, we should naturally conclude eituer 





Schwertz. 


Block. 


Petri. 


Thaer. 


Pabst. 


Meyer. 


Middleton 


10 


10 


10 


10 


10 


10 


10 




11 


— 


10 


— 


— 


— 


— 




10 


10 


9 


9 


10 


— 


— 


flo 


w- 














e . 





43 


— 


45 


42 


— 


— 




9 


__ ■ 


9 


9 


10 


— 


— 






20 


36 


45 


30 


15 


— 




40 


19 


18 


40 


20 


15 


— 




40 


20 


20 


40 


20 


15 


— 






16 


20 


13 


15 


15 


— 




20 


22 


20 


20 


20 


15 


— 







40 


— . 


— 


— 


— 


— 




27 


37 


25 


30 


25 


23 


34 




45 


53 


60 


52 


45 


29 


80 




4 


3 


6 


6 


— 


— 


— 






3 


6 


— 


5 


5 


— 




— 


4 


7 


— 


6 


— 


-?- 



614 THEORETICAL NUTRITIVE VALUES. 

that the different kinds of fodder vary very much in quality, or that those 
who determined their relative values by experiment must have tried 
their effects upon very different kinds of stock, fed probably also for dif- 
ferent purppses. Both of these conclusions are no doubt true. We 
know that the same kind of produce does vary very much in chemical 
constitution, but it is not likely that different samples of the same kind of 
turnip are so unlike each other that 29 lbs. of the one will go as far in 
feeding the same animal as 80 lbs. of another. These great differences 
in the table, therefore, seem to show that different kinds or varieties of 
fodder have been used, orunder different circumstances, or results so dis- 
cordant could scarcely have been obtained. 

A certain value, il is true, attaches to tlie numbers in the table when 
those given by the different authors nearly agree. Thus, about 20 of 
potatoes and 30 of carrots appear to be equal in nutritive value to 10 of 
hay. It must be confessed, however, that this subject of the experimental 
value of different kinds of farm produce in feeding stock of the same 
kind for the same purposes is still almost wholly uninvestigated. "Will 
none of the skilful stock feeders, of whom so many are now springing 
up, turn their attention to this interesting field of experimental inquiry ? 

2°. Theoretical values. — But the theoretical values of different kinds 
of food in reference to a particular object, can be determined by analyti- 
cal investigations made in the laboratory. This has been done in a 
very able manner by Boussingault, in reference to the value of different 
kinds of fodder in the jnoduction of muscle. These values, according to 
his analyses, are as follow, 10 of hay being again taken as a standard : — 

Theoretical quantities of different kinds of vegetable produce which ivill 
produce equal effects in the growth ofrnuscle [Boussingault) : — 



Hay 10 

Clover hay, cut in flower . . 8 

Lucerne do 8 

Aftermath do 8 

Green clover, in flower ... 34 

Green lucerne 35 

Wheat straw 52 

Rye straw 61 

Barley straw 52 

Oat straw 55 

Pea straw 6 

Vetch straw 7 

Potato leaves 36 

Carrot leaves 13 

Oak leaves 13 

This table possesses much value. 



Potatoes 28 

Old potatoes 41 

Carrots .35 

Turnips 61 

White cabbage 37 

Vetches 2 

Peas 3 

Indian corn 6 

Wheat 5 

Rye 5 

Barley 6 

Oats 5 

Bran 9 

Oil-cake 2 

It cannot, however, be relied upon 



as a safe guide in all cases by the feeder, because of the differences in 
the composition of our crops, which arise from the mode of culture and 
the kind of manure employed. It possesses, however, a higher value 
from this circumstance — that as muscle in most animals forms the larger 
portion of their bulk, the order in which different kinds of vegetable food 
promote the growth of this part of the body, may in most cases be adopted 
as the order also of their relative values in sustaining animals and keep- 
ing them in ordinary condition. The same remark, however, will not 



EFFECT or MODE OF FEEOir^G ON THE MANURE. 615 

apply to animal food, since we may have a kind of animal food, such as 
gelatine, which would greatly promote the growth of muscle, but which, 
from its composition, is capable of ministering so little to the wants of 
the other parts of the body that it will not even support life for any length 
of time. 

§ 16. Effect of different modes of feeding on the manure and on the soil. 

There remains still one practical point in connection with the feeding 
of stock, to which I think you will feel some interest in attending. 

The production of manure is an object with the European farmer of 
almost equal importance with the production of milk or the fattening of 
stock. What influence has the mode of feeding or the purpose for 
which the animal is fed, upon the quantity and quality of the manure 
obtained ? 

1°. The quantity of the manure depends upon the quantity of food 
which is necessary to sustain the animal. With the exception of the 
carbon, which escapes from the lungs in the form of carbonic acid, and 
a comparatively small quantity of matter which forms the perspiration, 
the whole of the food which sustains the body is rejected again in the 
form of dung. 

Now the sustaining food increases with the size of the animal, with 
the coldness of the temperature in which it is kept, and with the quantity 
of exercise it is compelled to take. Large, hardly worked, much driven, 
and coldly housed animals, therefore, if ample food is given them, will 
produce the largest quantity of manure. It might be possible, indeed, to 
keep large animals for no other purpose but to manufacture manure — by 
giving them an unlimited supply of food, using means to persuade them 
to eat it, and causing them at the same time to take so much exercise as 
to prevent them from ever increasing in weight. 

2°. Quality of the manure. — The quality of the manure depends al- 
most entirely upon the kind of food given to an animal, and upon the 
purpose for which it is fed. 

a. The full-grown animal, which does not increase in weight, returns 
in its excretions all that it eats. The manure that it forms is richer in 
saline matter and in nitrogen than the food, because, as I have already 
explained to you in detail (p. 472), a portion of the carbon of the latter 
is sifted out as it were by the lungs, and diffused through the air during 
respiration. In other respects, whatever be rtie nature of the food — the 
quantity of saline matter or of gluten it contains — the dung will contain 
nearly the same quantities of both or of their elements. 

b. The case of the fattening animal again is different. Besides the 
sustaining food, there is given to the animal some other fodder which 
will supply an additional quantity of fat If this additional food be only 
oil, then the dung will be little affected by it. It will be little richer than 
the dung of the full-grown animal to, which the same sustaining food is 
given. 

But if the additional food contain other substances besides fat — saline 
substances, namely, and gluten — then these will all pass into the dung 
and make it richer in precise proportion to the quantity of this additional 
food which is given. Thus if oil-cake be given for the purpose of laying 
on fat— the usual sustaining food at the same time being supplied — the 



616 WHY OLD PASTURES CONTINUE RICH. 

dung will be enriched by all those other fertilizing constituents present in 
the oil-cake which are not required or worked up by the fattening animal. 

Hence it is that the dung of fattening stock is usually richer than that 
of stock of other kinds. Oil-cake would be a rich manure were it put 
i ito the soil at once; it is not surprising, therefore, that after it has 
l^.irted with a portion of its oil it should still add much to the richness of 
common dung. 

A knowledge of the kind of material, so to speak, which the animal 
requires to fatten it, explains in a considerable degree another practical 
fact of some consequence through which it is not easy at first sight to see 
one's way. There are in various parts of the island certain old pastures 
which, from time immemorial, have been celebrated for their fattening 
qualities. Full-grown stock are turned upon them year after year in the 
lean state, and after a few months are driven off again fat and plump and 
fit for the butcher. This, I have been told when on the spot, has gone 
on time out of mind, and yet the land, though no manure is artificially 
added, never becomes less valuable or the pasture less rich. Hence the 
practical man concludes that the addition of manure to the soil is un- 
necessary, if the produce be eaten off by stock — that the droppings of 
the animals which are fed upon the land are alone sufficient to maintain 
its fertility. 

But the reason of this continued richness of such old pastures is 
chiefly this — that the cattle, when put upon them, are usually full-grown 
—they have already ©btained their full supply of bone and nearly as 
much muscle as they require. While on the fields they chiefly select 
fat from the grasses they eat, returning to the soil the phosphates, saline 
substances, and most of the nitrogen which the grasses contain. Their 
bodies are no doubt constantly fed or renewed by new portions of these 
substances extracted from the food they eat, but they return to the soil an 
equal quantity from the daily waste of their own bodies — and thus are 
indebted to, and carry off the land, little more than the fat in which 
they are observed daily to increase. 

But as the materials of the fat may be, and no doubt originally are, 
derived wholly — perhaps indirectly, yet wholly — from the atmosphere, 
the land is robbed of nothing in order to supply it, and thus may con- 
tinue for many generations to exhibit an equal degree of fertility. 

I give this only as a general explanation, by which the difficulty 
may be solved, where no other more likely explanation can be found 
in the Local circumstances of the spot, or of the district in which such 
rich old pastures exist. 

c. The growing animal, again, does not return to the soil all it re- 
ceives. It not only discharges carbon from its lungs, but it also extracts 
phosphates from its food to increase the size of its bones, gluten to swell 
out its muscles, and saline substances to mingle with the growing bulk 
of its blood. The dung of the growing animal, therefore, will not be so 
rich as that of the full-grown animal fed upon the same kind and quan- 
tity of food. Hence from the fold-yard, where young stock are reared, 
the manure will not be so fertilizing, weight for weight, as from a yard 
in which full-grown or fattening animals only are fed. 

d. The milk cow exhausts still further the food it eats. In the leau 



THE GROWING ANIMAL AND THE MILK COW. 617 

milk cow, which has little muscle or fat to waste away, and, therefore, 
little to repair, the sustaining food is reduced to the smallest possible 
quantity. This small portion of food is all that is returned to the hus- 
bandman in her dung. The phosphates, salts and gluten, and even the 
starch, of the remainder of the food she eats, are transformed in her 
system, and appear again in the form of milk. The dung of the milk 
cow must be very much poorer, and less valuable, compared with the 
food she eats, than that of any other kind of stock. 

It is true that the bulk of her dung may not be very much less than 
that of a full-grown animal which is yielding no milk, but this bulk is 
made up chiefly of the indigestible woody fibre and other comparatively 
useless substances which her bulky food contains. The ingredients of 
the milk have been separated from tliese other substances as the food 
passed through her body, and hence, though bulky, the dung of the milk 
cow is colder and less to be esteemed than that of the dry cow or of the 
full-grown ox. 

Nothing can more strikingly illustrate the difference between the effect 
of the digestive organs of the fattening ox and those of the milk cow 
upon the food they consume, than the well-known and remarkable dif- 
ference in quality which exists between distillery dung, obtained from 
fattening cattle fed upon the refuse of the distilleries, and Colo-feeders' 
dung, voided by milk cows fed upon nearly the same kind of food — 
namely, the refuse of the breweries. 

§ 17. Summary of the views illustrated in the present Lecture. 

The topics discussed in this Lecture are of so interesting a kind, and so 
beautifully connected together, that you will permit me, I am sure, 
briefly to draw your attention again to the most important and leading 
points. 

1°. It appears that all vegetables contain ready formed — that is, 
form during their growth from the food on which they live — those sub- 
stances of which the parts of animals are composed. 

2°. That from the vegetable food it eats, the animal draws directly 
and ready-formed the materials of its own body — phosphates to form the 
bones — gluten, &c., to build up its muscles — and oil to lay on in the 
form of fat. 

3°. That durn)g the process of respiration a full grown man throws 
off' from his lungs about 8 oz. — a cow or horse five times as much — of 
carbon every 24 hours ; and that the main office of the starch, gum, and 
sugar of vegetable food is to supply this carbon. In carnivorous animals 
it is supplied by the fat of their food — in starving animals, by the fat of 
their own bodies — and in young animals, which live upon milk, by the 
milk sugar it contains. 

4°. That muscles, bone, skin, and hair undergo a certain necessary 
daily waste of substance — a portion of each being removed every day 
and carried out of the body in the excretions. The main function of the 
gluten, the phosphates, and the saline substances in the food of the full 
grown animal, is to replace the portions of the body which are thus re- 
moved, and to sustain its original condition. Exercise increases this na- 
tural waste and accelerates the breathing also, so as to render necessary 



618 SUMMARY OF THE VIEWS ILLUSTRATED. 

a larger sustaining supply of food — a larger daily quantity to keep the 
animal in condition. 

5°. That the fat of tlie body is generally derived from the fat of the 
vegetable food — which fat undergoes during digestion a change or trans- 
formation by which it is converted into the peculiar kinds of fat which 
are S])ecially fitted to the body of the animal that eats it. In carnivor- 
ous animals, the fat is also derived directly from the fat of their food — 
which is, in like manner, changed in order to adapt it to the constitution 
of their own bodies. In cases of emergency, it is probable that fat may 
be formed in the animal from the starch or sugar of the food. 

6°. In the growing animal, the food has a double function to perform, 
it must sustain and it must increase the body. Hence, if the animal be 
merely increasing in fat, the food, besides what is necessary to make up 
for the daily waste of various kinds, must also supply an additional pro- 
portion of oil or fat. To the growing animal, on the other hand, it must 
supply also an additional quantity of gluten for the muscles, and of phos- 
phates for the bones. If to each of a number of animals, equal quantities 
of the same kind of food be given, then those which require the smallest 
quantity of food to sustain them will have the largest proportion to con- 
vert into parts of their own substance. Hence, whatever tends to in- 
crease the sustaining quantity — and cold, exercise, and uneasiness do so 
— will tend, in an equal degree, to lessen the value of a given weight of 
food, in adding to the weight of the animal's body. To the pregnant 
and to the milk cow the same remarks apply. The food is partly ex- 
pended in the production of milk, and the smaller and leaner (he cow is, 
less food being required to sustain the body, the more will remain for the 
production of milk. 

7°. Lastly, that the quantity and quality of the dung — while they de- 
pend in part upon the kind of food with which the animal is fed — yet 
even when the same kind of food is given, are materially affected by the 
purpose for which the animal is fed. If it be full-grown and merely 
kept in condition, the dung contains all that was present in the food, ex- 
cept the carbon that has escaped from the lungs. If it be a growing 
animal, then a portion of the phosphates and gluten of the food are re- 
tained to add to its bones and muscles, and hence the dung is something 
less in quantity and considerably inferior in quality^ to that of the full- 
grown animal. 

So it is in the case of the milk cow, which consumes comparatively 
little in sustaining her own body, but exhausts all the food that passes 
through* her digestive organs, for the production of the milk which is to 
feed her young. 

The reverse takes place with the fattening ox. He takes little else 
from the rich additional food he eats but the oil with which it is intended 
that he should invest his own body. Its other constituents are for the most 
part rejected in his excretions, and hence the richness and high price of 
his dung. 



Such are the main points I have endeavoured to illustrate to you in 
this Lecture-^they involve so many interesting considerations, both of a 



COiXCLUDIiNG SECTION. 619 

theoretical and of a practical kind, that had my limits permitted 1 could 
have wished to dwell upon them at still greater length. 

§ 18. Concluding Section. 

I have now brought the subject of these Lectures to a close. I have 
gone over the whole ground which in the outset I proposed to tread. It 
is the first time, I believe, that much of it has been trodden by scientific 
men, and I have endeavoured in every part of our journey to lay before 
you, as clearly as I could, everything we knew of the country we passed 
over, in so far as it had a practical bearing or was likely to be suscepti- 
ble hereafter of a practical application. 

In the first Part, I directed your attention to the organic portion of 
plants — showed you of what substances it consisted — on what kind of 
organic food plants live — and by what chemical changes the peculiar 
organic compounds of which they consist are formed out of the organic 
food on which they live. 

In the second Part, I explained in a similar way the nature, composi- 
tion, and origin of the inorganic portion of plants. I dwelt, also, upon 
the nature, origin, and natural differences which exist among the soils on 
which our crops are grown, and from which the inorganic constituents of 
plants are altogether derived. This led me to exj)lain the connection 
which exists between Agriculture and Geology, and the kind of light 
which this interesting science is fitted to throw upon the means of prac- 
tically improving the soil. 

h\ the third Part, I dwelt upon the various means which may be 
adopted for increasing the general productiveness of the land — -whether 
these means be of a mechanical or chemical nature. The whole doc- 
trine of manures was here discussed and many suggestions offered to 
your notice, which have already led to interesting practical results. 

In the fourth Part, I have explained the chemical composition of the 
several kinds of vegetable produce which are usually raised for food — 
showed upon what constituents their nutritive values depend — and how 
soil, climate, and manure afiect their composition and llieir value as 
food. The nature and composition of milk and of its products — butter 
and cheese — the theory of their manufacture, and the circumstances upon 
which their respective quantities and qualities depend — and, lastly, the 
way in which food acts upon and supports the animal body, and how the 
value of the manures they make is dependent upon the purpose for 
which the animal is fed — these subjects have also been considered and 
discussed in this fourth Part. 

In discussing new topics I have had occasion to bring before you many 
new views. This, however, I have not done lightly or without consi- 
deration, and I feel it to have been one of the greatest advantages which 
have attended the periodical form in which these Lectures have been 
brought before the public, that it has allowed me leisure to think, to in- 
quire, and to make experiments in regard to points upon which it was 
difficult at first to throw any satisfactory light. It is gratifying to me to 
know that the general diffusion which these Lectures have obtained, has 
already done some service to the agriculture of the country. 

r I N I s. 



1 



APPENDIX: 



CONTAINING 



SUGGESTIONS FOR EXPERIMENTS IN PRACTICAL AGRI- 
CULTURE, WITH RESULTS OF EXPERIMENTS 
MADE IN 1841, 1842, AND 1843. 



ii 



CONTENTS. 



AFifBNSxa:. 



L Suggestions for experiments in 
practical agriculture p. 1 

II. Effect of sudden alternations of 
temperature 11 

III. Results of experiments in practical 

agriculture made during ttie spring 

and summer of 1841 — 

At Aslce Hall 13 

At Ersklne 16 

At Barochan — 

1. On hay 17 

2. On winter rye 18 

3. On wheat 19 

4. On potatoes 20 

5. On moss oats 21 

6. On oat.<!, with sulphate and ni- 

trate of soda, as a top-dressing. .22 

7. On peas and beans, with sulphate 

of soda 23 

8. On nitrate of soda as a top-dress- 

ing for gooseberry and currant 
bushes 23 

IV. Suggestions for comparative ex- 

periments with guano and other 
manures 24 

V. Of the examination and analysis of 

soils 27 

Determination of the physical pro- 
perties of the soil ib. 

of the organic matter present in 
the soil 29 

Of the soluble saline matter in the" 
soil 31 

Determination of the quantity of 
the several constituents of the 
soluble saline matter .33 

Of the insoluble earthy matter of 
the soil.. 37 

VI. Different theories of the action of" ' 

gypsum 39 

VII. Suggestions for experiments with 

the silicates of potash and soda... 40 
Vni. Results of experiments in practical 
agriculture made in 1842 — 
A. Experiments on turnips— 

1. Made at Lennox Love 42 

2. Made at Barochan 43 to 46 

3. Made at Southbar 46 

4. Made at Muirkirk , lb. 

5. Effect of gypsum on the tur- 

nip crop ,.,,47 



VIII. 



IX. 



X. 



Results of experiments in practi- 
cal agriculture made in 1842— 

B. Experiments on potatoes — 

1. Those of Mr. Campbell, of 

Craigie p. 47 

2. Those of Mr. Fleming, of 

Barochan 47 to 51 

C. Experiments upon barley 51 

D. Experiments upon oats — 

1. Those of Lord Blantyre 52 

2. Those of Mr. Fleming 53 

E. Experiments upon wheat — 

1. Thoseof Lord Blantyre 53 

2. Those of Mr. Fleming 54 

3. Those of Mr. Burnet, of Gad- 

girth ib. 

F. Experiments upon pasture and 

other grasses — 

1. Those of Mr. Alexander 65 

2. Those of Mr. Fleming 56 

3. Those of Mr.Campbell,of Isla.ib. 

G. Experiments upon mixed crops 

by Mr. Alexander 57 

H. Experiments upon beans — 

1. Those of Mr. Alexander ib. 

2. Those of Lord Blantyre ib. 

I. Effect of the top-dressings ap- 

plied in 1841 upon the crop 
ofl842 58 

II. Remarlis upon the experiments 

of 1842 ib. 

A. The experiments on turnips... 59 

B. The experiments on potatoes. .64 

C. The experiments on barley... 67 

D. The experiments on oats ib. 

E. The experiments on wheat 68 

F. The experiments on grass 71 

G. The experiments on mixed 

crops 73 

H. The experiments on beans. ...ib. 
Results of additional experiments 

made in 1812 75 

Remarks nn these experiments... 78 
Experiments in practical agricul- 
lure made in 1843 by Mr. 
Fleming, of Barochan — 

1. With suano upon potatoes. . .83 

2. On hay .85 

3. On oats ye 

4. On turnips 87 

Remarks on tbe.se experiments.. .89 



I 



APPENDIX. 



No. I. 



SUGGESTIONS FOE EXPERIMENTS IN PRACTICAL AGRICULTURE 
DURING THE ENSUING SPRING AND SUMMER. 

One of the most important objects which chemistry is at present desirous of 
attaining for the improvement of practical agriculture, is the discovery and ap- 
plication of specific or special manures. 

We know that certain substances, such as fold-yard manure, are capable of 
fertilizing to a considerable extent almost any land, and of causing it to yield 
a better return of almost any crop. But we know also that manures or fertili- 
zers of nearly every kind are more efficacious on one soil than on another, and 
that some answer better also for one species of crop than for another. The 
case of gypsum will serve to illustrate both these positions. 

The effects of gypsum in the United States, in Prussia, and other parts of 
Germany, and in some districts of England, are said to be absolutely astonish- 
ing • while in many other parts of our Island, of Germany, and even of the 
United States, the benefit derived from it has not repaid the trouble and expense 
incurred in applying it. Gypsum, therefore, \s especially adapted for use in cer- 
tain soils only. . j- .• ^i 
. Again the remarkable effects of gypsum have been observed most distinctly 
on clover* and certain kinds of grass. The same benefits have not follo\^d, 
to any thing like an equal extent, from its use on barley, oats, wheat, or other 
kind of grain. Therefore, while specially adapted to certain soils, it is alsd 
specially adapted to certain crops. It is a kind of specific manure for clover 
and some of the grasses. . . 

Now, neither of these subjects which it is so important to investigate,— 
neither that of the manures which are especially fitted for each soil, nor of those 
which are specially fitted for each crop,— can be determined either from th^ry 
or from experiments devised and executed in the laboratory of a chemist. The 
aid of the practical farmer, of many practical farmers, must be called in. Nu- 
merous experiments, or trials, must be made in various localities, and by differ- 
ent individuals,— all, however, according to the same rigorous and accurate 
method,— in order that, from the comparison of many results, something like a 
general principle may be deduced. • r -r 

It is partly with a view to determine the mode of action of certain fertihzers, 
and partly in the hope of obtaining some additional light on the subject of 
manures specificaUy adapted to particular crops, that I venture to suggestto you 
the propriety of making one or more of the following sets of experiments, 
during the spring and summer of the present year. I could have much enlarged 

• In regard to its use in Germany, Lampadius says,—" It may with certainty, be stated, 
that by the use of gypsum the produce of clover and the consequent amount of hve stocfc 
have been increased at least one-third." —Di^ Lehre von den Mineralischen Dungmit- 

TBLN, p. 34. 

A 



$ 



3 OP GRASS AND CLOVER. [Appendix, 

the list of suggestions, but I neither wish to fatigue your attention, nor to place 
before you more work of the kind than can be readily accomplished, wl(/i little 
expense of time, labour, or money. Another season will, I hope, afford us an 
opportunity of interrogating nature by further, and perhaps more refined, modes 
of experimenting. 

1. OF GRASS AND CLOVER. 

1°. It is beyond dispute, that on certain soils, gypsum causes a largely in- 
creased growth of grass and clover, but experiment alone appears capable of 
determining on what soils it is likely to be thus beneficial. ISuch experiments, 
therefore, ought to be made on every farm, on a small scale at first, and at little 
cost,* but made with care and accuracy, and with a minute attention to weights 
and measures. 

2°. The action of gypsum appears to be entirely chemical, but the only ex- 
planation of this action yet attempted is far from being satisfactory. It is desi- 
rable therefore, that experiments with other substances should be made, which 
are likely to throw light on the theory. Important practical results may at the 
same time be obtained— they are sure, indeed, to follow from a right under- 
standing of the theory. 

In the neighbourhood of Lyons, it has been found that veiy dilute sulphuric 
acidt (oil of vitrol) exhibits the same beneficial effect upon clover, that has else- 
where attended the use of gypsum. It is desirable, therefore, that a compara- 
tive experiment should be made with this acid on a portion of the same field to 
which the gypsum is applied. Where the one fails the other may act. 

3°. It was observed by Dr. Home, of Edinburgh, so early as the year 1756, 
that sulphate of sodaj: had a remarkable effect in promoting the growth of plants 
—its action being nearly equal to that of saltpetre or nitrate of soda. This fact, 
though mentioned by Lord Dun^onald, has been lost sight of by practical men' 
the sulphate of soda being generally represented as too high in price to be avail- 
able as a fertilizer.§ The use of saltpetre, however, and of nitrate of soda, both 
of which are more than double the price of sulphate of soda, show that the cost 
of this latter article should not stand in the way of an accurate trial of its value 
as a fertilizer on various crops. Dry sulphate of soda can be readily obtained 
firom any of the alkali works on the Tyne,ll and being an article of domestic 
mgjiufacture, it is proper that its merits should be ascertained, and, if it can be 
available, that its use should be encouraged. 

From the circumstance of its containing sulphuric acid, therefore, I would 
recommend that it should be tried on clover and grass, in comparison with 
gypsum and sulphuric acid, and on a portion of the same field. It may suc- 
ceed where the others fail. 

4°. Nitrate of soda also, as a top-dressing on grass land, has been oflen used 
with great benefit. I have seen grassland in Dumfriesshire, which, after being 
long let for pasture at 30s. an acre, had been sprinkled with an annual top- 
dressing of nitrate of soda at the rate of 20s. an acre, and had since readily let 
at £4: an acre, yielding thus an annual profit of 30s. an acre to the landlord. 

In other districts, again, it has been found to answer better for corn. Thus, 
after a discussion on this subject in the Gloucester Farmers' Club, it was agreed' 
that nitrate of soda " was a very valuable manure for white straw crops, but 

* The price of gypsum in London is about 2s. 6d. per cwt. ; in Newcastle, 3s. 

t Gypsum consists of sulphuric acid and lime. 

X Glauber soZis— consisting of sulphuric acid and soda. 

§ LordDundonald says—" From experiments it has been proved fo promote vegetation in 
a very high degree. The high price at present of this article precludes the use of it, but 
could It be made and sold at a cheap rate, it would prove a most valuable acquisition to agri- 
culture. Since the time of Lord Dundonald some trials made in Germany have shown it 
to have a beneficial action on i-ye, potatoes, and fruit trees. 

II Messrs. Allan & Co., of the Hewonh Alkali Works, deliver it in Newcastle and the neiah- 
bounng towns, at 9s. or 10s. per cwt. * 



No. /.] OF GRASS AND CLOVER. 3 

when applied to green crops the benefit was not sufficiently great to counter-bal- 
ance the expense." In Northumberland, where it has been tried in a skilful 
manner by Mr. Gray, of Dilston, it was found to yield a most profitable return 
on both hay and barley. 

These results show the necessity of further trials, not only for the pui-pose of 
illustrating the cause of the beneficial action of this saline substance, but also 
with the view of amving at some general rule by which the practical man may 
be guided in determining on what fields, and for what crops on those fields, the 
nitrate of soda may be beneficially applied 

This experiment, like the others above-mentioned, will be much more valua- 
ble, if made in such a way that the result can be compared with that obtained 
by the use of other chemical agents. I would, therefore, propose that in the 
same field of grass or clover, a portion should be measured oflf, to be top- 
dressed with nitrate of soda, that thus not only the absolute, but also the com- 
parative, weight of the produce may at the same time be ascertained. 

5°. There are other trials also, from which this general subject is capable of 
receiving illustration. The fertilizing power of gypsum has been explained by 
its supposed action on the ammonia which is presumed to exist in the atmos- 
phere. If this be the true explanation, ja substance containing ammonia should 
act at least as energetically. At all events, the action of fold-yard manure and 
of putrid urine is supposed to depend chiefly on the ammonia they contain or 
give off. Now, among the substances containing ammonia in large quantity, 
which in most towns are allowed to run to waste, the ammoniacal liquor of 
the gas works is one which can easily be obtained, and can be applied in a li- 
quid state at very little cost. It must be previously diluted with water till its 
taste and smell become scarcely perceptible, 

I would propose, therefore, as a further experiment, that along with one or 
more of the substances above-mentioned, the ammoniacal liquor of the gas 
works should be also tried, on a measured portion of ground, and, if possible, 
in the same field. 

6°. Soot, as a manure, is supposed to act partly, if not chiefly, in conse-. 
quence of the ammonia it contains. In Gloucestershire it is applied to pota- 
toes and to wheat, chiefly to the latter, and with great success. In the Wolds 
of Yorkshire it is also applied largely to the wheat crop, at the rate of about 24 
bushels to the acre.* In this county it is frequently used on grass land, to the 
amount of 20 bushels an acre, and though I am not aware that it is extensively 
employed upon clover, I am inchned to anticipate that the sulphur it contains,t 
in addition to the ammonia, would render it useful to this plant. At all events, 
comparative experiments in' the same field with the gypsum and the ammonia- 
cal liquor, are likely to lead to interesting results. 

7°. Common salt, highly recommended as a manure by some, has been as 
much depreciated by others, and hence, when directly applied, is considered as 
a doubtful fertilizer by almost all. The obscurity in regard to its use, however, 
rests chiefly on the quantity which ought to be employed. The result of com- 
parative experiments made in Germany, showed that a very few pounds per 
acre were sufficient to produce a largely increased return of grass — while in 
England it has been beneficially applied within the wide limits of from five to 
twenty bushels per acre, and, when used for cleaning the land for autumn, of 
thirty bushels an acre. 

Among the comparative experiments upon gi-ass and clover here suggested, 
the eflect of salt might also be tried with the prospect of practical benefit. It 
would give an additional interest to the experiments and supply an additional 
term of comparison. 

' The price is from 6d. to le. a bushel. In this county the soot is said to be often of an 
inferior quality, and brings therefore a less price. 

t The gypsum, I might also say, for much of our soot contains gypsum, the lime being 
derived chiefly from the sides of the flue. 



OP GRA6S AND CLOVER. 



[Appeoulix, 



The entire series of experiments, therefore, which I would rccommend, would 
occupy eight patches on a clover or grass field, one of whicli would be left un- 
dressed for the purpose of comparison. Thus, each plot being half an acre: 



Gypsum. 


Sulphate of 

Soda, 


Ammoniacal 
Liquor. 


Sulphuric 
Acid. 


Nitrate of 
Soda. 


Common 

Salt. 


Soot. 



The ammoniacal liquor and the soot are placed as far as possible from the 
gypsum and sulphuric acid, tliat they may not interfere with each other's action. 
In a large field they might be placed still farther apart, and other trials might be 
made in one or two of the vacant places. 

The appearance of each patch should be entered, loitk the date, in an experi- 
ment book, at weekly intervals, and the final produce both of hay and of after- 
math carefully noted, both as to weight and quality. 

Nor will the experiment be completed when the crop for the year is gathered 
in ; but, where it is possible, two further points should be ascertained, — 

1°. The relative feeding or nourishing properties of the produce. To those 
who rear and fatten cattle, this is a matter of great importance, and it is one 
which they could easily determine, at least very approximately. 

2'^. What has been the permanent effect of tlie sevei-al substances on the soil, 
as indicated by the comparative quantity and quality of the crop obtained from 
each half acre, on the siccceeding or during the two following years. The result of 
these further observations may matei-ially modify the conclusion we should draw 
from the comparative weight and quality of the produce of the first year. 

I shall only observe, in conclusion, on this head, that the result of a simulta- 
neous trial of all these substances in the same field would not only throw much 
light on the specific action of each on the grass or clover in general, but would 
be of permanent utility to that farm or locality in wliich the experiments were 
made. It would indicate the kind of fertilizer which was best adapted to the 
farm or neighbourhood, in the existing condition of its general culture. It would 
form a local record, useful not only to the tenant who made the experiment (if 
well made) and by whom the farm at the time was tenanted, but more useful 
by far, and more permanently so, to the owner of the land, whose interest in it 
is supposed to be not only gi-eater, but much more lasting. 

In regard to the quantities of the several substances above-mentioned, which 
are to be applied to each acre, they may probably be varied according to cir- 
cumstances, but the following may be recommended in the comparative experi- 
ments: 

1°. Gypsum 2 to 3 cwt. per acre. 

2°. Sulphate of Soda 1 cwt. per acre. 

3°. Nitrate of Soda 1 cwt. per acre. 

4°. Soot 20 bushels per acre — this in different districts may be varied accord- 
ing to the known quality of the soot. 

5°. Of Sulphuric Acid from 30 to 40 lbs. per acre, applied at tliree or four 
several intervals — and diluted with at least 200 times its weight of water. Or 
so much water may be added as to make it perfectly tasteless, or so weak as 
not sensibly to injure the texture of a plant lefl in it during the previous night.* 

6°. Of Ammoniacal Liquor 100 to 200 gallons per acre, according to its 
strength, for this is constantly varying. It must also be diluted with so large a 
quantity of water as will render it perfectly tasteless, and is likely to prove most 
beneficial if laid on at several successive periods. 

* The quantity above mentioned amounts to about two gallons of the acid of the shops, and 
it Bhould be diluted with three or four hundred gallons of water. 



No. /.] OF WHEAT, BARLEY, AND OATS, 5 

7°. Of common salt it will be safer to apply not more than four to six bushels 
an acre ; though, where time and circumstances permit, comparative trials might 
also be made on the efficacy of salt when applied in different proportions, to the 
sai/ie land on which the other experiments are made. 

As to the time when these sevei-al dressings ought to be applied, some varia- 
tion may be made according to the state of the young crop. They need not, in 
general, be used before the lOth of April, and they should rarely be later 
than the middle of May. 

It will be desirable that in the detail of every set of experiments, the kind and 
quality of the soil (and subsoil) should be stated — with its drainage and expo- 
sure — and the kind of grass or clover which had been sown upon it. 

II. OF WHEAT, BARLEY, AND OATS. 

It is known that saltpetre and nitrate of soda produce highly beneficial effects 
on all these varieties of grain. There remains much to be done, however, be- 
fore the principle of their operation, or the circumstances on which their most 
useful application depends, can be clearly understood. Their relative effects on 
the same kind of grain must be made the subject of more frequent, more precise, 
and more carefully conducted experiments — and these effects must be cornpared 
with those of other fertilizing substances, in order that we may arrive ultimate- 
ly at some comparative estimate of the practical value of each, in increasing the 
growth and produce of those crops which are the staples of animal food. 

A.— Of Wheat. 

It is confidently stated by some, as a general rule, that saltpetre is more ad- 
vantageous than nitrate of soda, when applied to wheat. On the other hand, it 
is beyond question that the application of nitrate of soda to wheat has been 
found productive of remarkable benefit. 

Is saltpetre especially adapted for wheat of all varieties, on all soils, and under 
every variety of management, and is nitrate of soda, in hke manner, especially 
fitted for barley and oats 1 

These are questions to which the experiments hitherto made do not enable us 
to give a reply. New data must be obtained before we can have the means of 
reasoning usefully in regard to any of them. I would propose, therefore, — 

1°. That where two varieties of wheat are sown on the same field, or on dif- 
ferent fields of precisely the same kind of land and in the same condition, that 
two half acres of each variety should be measured off, and that one half acre of 
each should be dressed with saltpetre, and the other with nitrate of soda, at the 
rate of 1 cwt. per acre. If three varieties could be so treated, the experiment 
would be the more valuable. 

It would thus be determined how far the effect of each of these nitrates was 
dependent upon the variety of wheat sown — and what was the relative action of 
each nitrate upon any of the varieties. 

2°. That when the same varieties of wheat are sown upon two or more dif- 
ferent soils— in different parts of a farm— that one portion of the wheat on every 
different soil should be dressed with nitrate of soda, and another with nitrate of 
potash (saltpetre). By this experiment, it would be shown how far the effect 
of these substances is dependent on the nature of the soil, and how far the action 
of the one, compared with that of the other, is modified by diversity of soil. 

In these different experiments, the management is presumed to be the same. 
If the experiments be repeated by several persons in different parts of the coun- 
try, the effects of difference of management will, in a great measure, be shown 
in the diversity of the results. 

3°. With the view of ascertaining the comparative effect of the sulphate of 
soda on this crop, I would suggest that in each case above specified, an equal 
area should be set aside to be dressed with this salt, in the proportion of 1 cwt. 
per acre. 

Of each variety of wheat, therefore, and on each variety of soil, four patches 



6 



OP WHEAT, BARLEY, AND OATS. 



[AppenaiXy 



Nitrate of 
Soda. 


Saltpetre. 




Sulphate of 
Soda. 



of equal area, say half an acre, should be measured off— one of which should be 
undressed for the purpose of comparison : thus — 

As before, the nature of the soil and the kind of 
gram must be recorded— the appearance of each patch 
noted week by week— with the time of ripening and 
reapmg— and the respective qualities and weights of 
the gram and straw collected from each half acre. 

The quantity of gluten contained in the wheat 
should also be determined, or a sample of the flour 
transmitted for the purpose to the writer of these sug- 
gestions, accompanied by a detaU of the experiments they are intended to 
Illustrate. 

B. — Of Barley and Oats. 

To barley and oats the above remarks all apply, with this difference that to 
these crops saltpetre is said to be less beneficial than the nitrate of soda In 
connection with these crops, however, I would make the following additional 
observation. 

According to any theory of the action of the nitrates of potash and soda 
which readily presents itself, their effect on any crop which they are equaUv 
capable of benefitting ought to be nearly equal, weight for weight. The nitrate 
of soda ought to have a decidedly more powerful action, were it not that the 
state of moisture in which it is generally sold, increases its weight so much as 
in a great measure to deprive it, in equal weights, of this superiority. 

But while 1 cwt. of saltpetre (nitrate of potash) is recommended as a suffi- 
cient dressing for an acre, li to U cwt. of nitrate of soda is recommended for 
an equal area. It would, therefore, be desirable where nitrate of soda is applied 
to any large extent of land, either with oats or barley, to make a comparative 
trial on three equal portions of the same field, with 1, U, and 1^ cwt oer acre 
respectively. - • t^ > 

In addition, therefore, to the experiments suggested in regard to wheat with 
the view of determining— ■ > ^ ' 

1°. The absolute and relative eflicacy of saltpetre and nitrate of soda on dif- 
ferent varieties of the grain ; 

2°. The same on different varieties of soil ; 

3°. And under diversities of management,— as in the previous treatment of 
the land, &c. ; 

There may be added, in regard to oats and barley, another series of trial to 
determine — 

4° The relative effects of the different proportions of the nitrate of soda 
which IS at present supposed to be specially beneficial to these kinds of grain' 
It any one be desirous of uniting this latter series with the fonner, it may be 
done thus — ' ■' 

The vacant half-acre being as before left 
for the purpose of comparison. Such an 
entire series might be made at the same 
time on a field of Tartary and of potatoe 
oats, and on two or more varieties of bar- 
ley. 

These top-dressings may all be sown 
, , , , . broad-cast — on the wheat most convenient- 

ly when the seeds are sown in April or May, and on the barley and oats when 
the fields have become distinctly green. 

I may be permitted to add, as inducements to practical men, to try one or 
more of these experiments in the accurate manner above described : 

1°. That the result will be directly available and of immediate practical value 
on his own farm, to the person by whom they are carefully made. That they 



Sulphate of 
Soda. 


Nitrate of 

Soda, 1 cwt. 

per acre. 


Saltpetre. 


Nitrate of 
Soda, 
li cwt. 




Nitrate of 
Soda, 
U cwt. 



iVb. /.] OF TURNIPS. 7 

will be permanently useful to his landlord (if carefully recorded), ought to be 
an inducement to the latter to give every facility and encouragement to his ten- 
ant in making them. , . , • • * 

2°. That, instead of involving expense and outlay, which in many instances 
may ill be spared, they are sure in almost every case to do more than repay the cost 
of making them, by the increased quantity or value of the produce obtained. 
Any of tlie series of experiments, on the scale suggested, may be made for five 
pounds so that were the outlay all to be lost, the accurate knowledge obtained 
in reference to the general tillage of his land, would be worth more money to 
the holder of a farm of a hundred acres. _ 

3°. I need scarcely add, as a further inducement, the additional interest which 
such experiments give to the practice of farming— and the means they afford 
of caUing forth the intelligence of the agricultural population. The moment a 
man begins to make experiments under the guidance of an understood principle, 
from that moment he begins to think. To obtain materials for thought he will 
have recourse to books— and thus every new experiment he makes, will further 
stimulate and awaken his intellect, and lead him to the acquisition of further 
knowled°-e. Does it require anything more than this general awakening of the 
minds of the agricultural class, to advance the science of agriculture as surely 
and as rapidly as any of the other sciences, the practical application of which 
have led to those extraordinary developments of natural resources which are 
the characteristic and the pride of our time ] 

III. OF TURNIPS. 

The raising of turnips is of such vast importance in the prevailing system 
of husbandry'^ that any improvement in the mode of culture must be of exten- 
sive and immediate benefit. Experiments so numerous and so varied have been 
made with this view, that it may almost seem superfluous in me now to rnake 
any further su^rgestions on the subject. But when experiments have been 
made witli a view to one subject only, it often happens in all departments ol na- 
tural science, that as new views are advanced or more precise methods pointed 
out, it becomes necessary to repeat all our former experiments,— either tor the 
purpose of testing the results they gave us, or of observing new phenomena to 
which our attention had not previously been directed. 

I Numerous experiments, for example, have been made upon the use of bones 
in the raising of turnips, but they have been chiefly directed to economical ends 
and so far with the most satisfactoiy results. But among fifty intelligent and 
thinking practical men, and who all agree in regard to the profit to be derived 
from the use of bones with the turnip crop, how many will agree in regard to 
the mode in which they act— how few will be able to give a satisfactory reason 
for the opinion they entertain ! The same is true of theoretical chemists, some 
attributing- their effect more especially to the earthy matter, others to the gelatine 
they contain. Dry bones contain about two-thirds of their weight of earthy 
matter, the other third consisting chiefly of animal matter resembling glue. Ut 
the earthy matter five-sixths consist of phosphate of lime and magnesia, and 
the rest chiefly of carbonate of lime. Thus a ton of bone dust will contain— 

Animal matter 74G lbs. 

Phospate of lime, &c 1245 

Carbonate of lime, &c 249 

2240 

On which of these constituents does the efiicacy of bones cluefly depend 1 
Does it depend upon the animal matter 1 This opinion is in accordance with the 
following facts : — , «. i i 

1° That in the Doncaster report it is said to be most effectual on calcareous 
soils,- for in the presence of lime all organic matter more rapidly decomposes. 



8 OP TcRNips. [Appendix. 

2°. Tliat horn shaving are a more powerful manure than bones —since 
horn contams only one or two per cent, of earthy matter * ' 

3° That before the introduction of cruslied bones, the ashes of burned bones 
had been ong employed to a small extent in agriculture, but have since fallen 
almost entirely into disuse. mucu 

4°. That old sheep skins cut up and laid in the drills, have been found to 
yield as good a crop of turnips and after-crop of corn, as the remainder of the 
field which was manured with bones. 

5°. That "40 lbs. of bone dust are sufficient to supply three crops of wheat 
clover potatoes, turnips, &c., with phosphates,"t while one to two-thirds of a 
lrapprd%XTani'"" ''' ^° ''' '''■ ^^ P^^^P^-^-' - ^he quantity usu- 

r'f^aV^^^ °^^'^'" ^'^"^' the quantity of animal matter present in a ton of bones 
(.74b lbs.) IS so small, and its decomposition so rapid during the growth of the 
hrpf-TT .u ^V'^' '^''^' *'"'" '^^ ^^''^'^ °f the bones are so lasting and so 
^hetZf V ' f'':^'% of corn-that many persons hesitate in con^sidering 
of ifflnl !u°^ phosphates applied to the land, as really without any shail 

of influence in the production of the crops > aic 

and r^.ff f""^-' ^u ^"t^o^^'y of the very highest character, both in theoretical 
^f^vS ; "^ agriculture is persuaded that the phosphates are the sole fertilizing 
efhtl '"aI'^I?' T^ ^^ ^""P^^^"" ^^'^ ^^"t '^f ^"^^^«s from the use of crush- 
soils in thn?e^n?^''''^T and North Germany, on the supposition that the 
m FnS.n^ countries already contain a sufficient supply of phosphates, while 
in i^ngland generally they are deficient in these compounds 
t]J^ifT' '^1 ^^^ ^"'"^^^ '''''"^' ^^ t^^ fertilizing agent in bones, why are not 

%•{ "^ efficacy on grass land as upon turnips ? ^ 

tivrpffl*,. JT"' t^^^'^^^^^^' of leading to some rational explanation of the rela- 
tive ettects of the several constituents of bones, it would be desirable to institute 
coniparative experiments of the following kind— institute 

oo' .^'^ ^^^^f ^ ton of bones per acre. 

?o' ^J^^^ ^^^^^ °^ ^°"^ ^^t- of ^^orn shavings or ghie per acre 
Jo" • t^° "^^t- °^ burned bones per acre. 
4 With six or seven cwt. of burned bones per acre 

The quantity of burned bones in No. 4 is that which is yielded bv a ton of 
fresh bones; that in No. 3 is upwards of five times what should be taken up bv 
the crops-as great part of what is added must be supposed to remain in the 
soil, while sortie must be dissolved and carried off by the rains 

The result of such experiments as these, if made accurately on different soils 
will lead us sooner to the truth than whole volumes of theoretical discussion 

II. Nitrate of soda has also been applied with great benefit in the culture of 
t^Iw^J' 1 ""^ experiments, exceedingly favourable in an economical point of 
view, have been made by Mr. Barclay, of Eastwick Park, Surrey,^ whS found 
that one cw . per acre, drilled in with the seed, gave as great a reiurn of Swedes 
as 15 bushels of bones with 15 of wood ashes pir acre, Ind whenTe nirrlte of 
soda was sown broadcast, from 20 to 25 per cent. more. In evSy part of the 
country, therefore, this substance ought to be tried. And as this nitrate is verv 
soluble in water, and may therefore be readily carried off by the rain and Is 
ha on y which is within reach of the plant is of any avail, I would su/ees? 
that not more than one-fourth of the wliole should be drilled in with the fed 

I Journal of the English Agricultural Society, I. p. 428. 



]Sl0^ /I OF TURNIPS. V 

this way the whole energy of the salt being expended where it is required, the 

greatest possible effect will be produced. . • . i.- t.i u 

III I have already stated the reasons which lead me to anticipate highly be- 
neficial effects to vegetation from the use of sulphate of soda ; I would suggest, 
therefore, a trial of this salt on the turnips also, at the same rate of 1 cwt. per 
acre and applied in the way above recommended for the nitrate of soda. Ut 
course the intelligent farmer will vary the proportions and mode of application 
of these substances, as his leisure or convenience permit, or as his better judg- 
ment may suggest to him. 

The entire series of experiments on turnips, above suggested may be repre- 
sented as follows, adding two plots for different proportions of the nitrate and 
sulphate of soda :— 



Burned Bones, 
2 cwt. per acre. 



Nitrate of Soda, 
1^ cwt. per acre. 



Burned Bones, 

6 or 7 cwt. per 

acre. 



Bone Dust, or 

Crushed Bones, 

1 ton per acre. 



Sulphate of 

Soda, 

1 cwt. per acre. 



Unmanured. 



Horn Shavinjrs, 
or Glue, 7 or 8 
cwt. per acre. 



Sulphate of Nitrate of 

Soda, Soda, 

U cwt. per acre. 1 cwt. per acre. 



Some of these experiments most of you may easily try. Those with the 
burned bones and horn shavings, which in this part of the country are less easy 
to be obtained, it is not to be expected that many of you will ^h^n^o^ ""f^™" 
in^ I hone however, that they will not be lost sight of by those who possess fa- 
ciUUes for obtaining them in sufficient quantity to make a satisfactory experiment 
In many parts of the United States, gypsum is the umversal fertilizer for 
every crop, and among the rest it is said to benefit turnips. The same opinion 
is entertained in Germany. I am not aware how far, in what way or with 
what results, it has been applied to the turnip crop m this country. A simple 
mode of test no- its efficacyf however, would be to strew it over the p ants when 
h^ the rouXfef on part of a field, the whole of which had been already ma- 
nured Inthe ordinary'way with fold-yard manure. The difference o^roduce 
would thus show its efficacy, m the given circumstances ; and the experiment 
could be made effectually at the cost of a single cwt. of gypsum 

I have not included rape dust among the trials above suggested, though it is 
undoubtedly under certain modes of management, a beneficial manure both to 
corn and turnip crops. There is also a diversity of opinion as to the cause of 
[t^ fertilizing action, as well as a manifest difference m the effect of different 
samples of the dust on the same soil. Though, therefore certain expenments 
which I may on a future occasion suggest, would undoubtedly throw light on 
the cause of the good qualities of this manure, yet as its action (taking different 
sampks) is not fonstalt on the same soil, results obtained with it cannot pos- 
ses7the same importance, either theoretical or practical, as those which are ob- 
served to follow from the use of bones and of salme substances, the composi- 
tion of which is nearly invariable. . J * Tf 
Many farmers, however, are in the habit, of constant y using rape dus . If 
any of these could conveniently make experiments on tl^^^ effect of different sam- 
ples of the cake, from different kinds of seed, and from different od mills, and 
would accurately note the results, they would perform an important service in 
TeXinff the way for that clear explanation of the cause of its fertihzing action, 
which is at present wanted,* and which experiment alone can discover to us. 

• Tf« onod effects are eenerally attributed to the oil which is left in the seed, and its vary- 
• lA^ir. ?hP ditferent auantities of oil left in it by different crushers. 1 doubt, however, 
iffh^ro^Suo KnsiSas mire than a seco^idary cause of its beneficial action. 
A* 



# 



10 OP POTATOES. [Appe7ldtX, 

IV. OF POTATOES. 

1°. Nitrate of soda has been applied with great benefit to potatoes also Af- 
ter the potatoes have been harrowed down and (hand) hoed, and the plants are 
four to SIX niches above the ground, it is applied by the hand round the stem 
of the plants, and the earth then set up by the plough. Mr. Tumbull in Dum- 
bartonshu-e, last year used it in this way at the rate of U to 2 cwt per Scotch 
acre, (li English acres,) and the produce exceeded that of the land to which no 
nitrate was applied, by 20 Scotch bolls to the Scotch acre. 

2°. Applied in the same way there is every reason to believe that the sul- 
phate of soda would have a highly beneficial effect also, I repeat my recom- 
mendation that this substance should be fairly tried with every crop because it 
is a product of our own manufactories, which can be supplied in unlimited 
quantity and without the chance of any material increase of cost • while the 
nitrate of soda is already in the hands of speculators, and within a short period 
has risen in the market to the extent of nearly one-third of its former price 

In plasknng their potatoes, the Americans generally put in a spoonfbl of 
gypsum with every cutting-a similar method, if preferred, might be adopted 
with the nitrate and sulphate of soda, though the chance of loss by percolation 
through the soil, would, by this method, be in some degree increased. In Flan- 
ders, wood ashes and rape dust are frequently thrown in by the hand, when each 
cutting is introduced. ' 

3° 1 shall have occasion hereafter to recommend to the attention of the prac- 
tical farmer, many waste materials of various kinds, thrown out from our manu- 
factories, the application of which to useful purposes would be a great national 
beneht. In reference to the culture of potatoes, I will here bring under your no- 
tice the chloride of calcium, which is said to have been beneficially applied to 
various crops, but to potatoes especially, with surprising effect. Under the in- 
fluence of this substance the sunflower and maize have grown to the hei-ht of 
14 to 18 feet, and potatoes have attained the weight of 2 to 3 lbs * In Germany 
feprengel also found it useful to potiUoes.—(C/iemie Jiir Lcmdwirtke, I. p. 635 ) 

1 housands of tons of chloride of calcium mav eveiy year be prepared from the 
waste materials which flow into the river Tyne, from the alkali works upon its 
banks Thousands of gallons of the solution of this substance yearly run off 
from the works of Messrs. Allan & Co at Heworth, and might be procured for 
httle more than the expense of collecting. It is also contained largely, thou-h 
mixed with other substances, in the mother liquor of the salt pans ; and from the 
numerous salt works on the coast might readily be obtained for trial When 
prepared in the dry state, this substance rapidly ddiqiiesccs and runs into a liquid 
Ihe most convenient way of applying it, therefore, would be in the state of so^ 
ution-so largely diluted as to have only a slight taste-and by means of a wa- 
tering cart so contrived as to allow it to flow on the tops of the ridges and vounff 
plants, by which unnecessary waste would be prevented ^ & 

Without knowing the strength of the solution likely to be obtained from the 
works, It IS impossible to give any idea of the quantity of the chloride of calcium 
which ought to be employed; but 500 gallons per acre may safely be used if 
the solution be so far diluted as to have only a decided taste of the substance 
I he experiments her e suggested, therefore, require four patches, as follows:— 
These experiments are supposed to be made in gi-ound 
already prepared for the potatoe crop, by the usual quan- 
tity of manm-e. I think it not unlikely, however, that 
by planting the potatoe in the midst of nitrate or sul- 
j phate (sprinkled over with diy soil) at the rate of i cwt 
Manure per acre, and afterwards applying 1 cwt. per acre, when 
'y- I the plants are hoed, a crop might be obtained without 
the use of manure. Of course, such an experiment as 



Nitrate of 
;Soda,ltol>^ 
cwt. pr acre. 



Chloride of 
Calcium, 500 
gals, pr acre. 



Sulphate of 
Soda, ltol>< 
cwt. pr acre. 



ordiM.^ mlSo^frSST/p/J.?^^^'^^"^ '^'^'y introduced into the United States-by the 
y mocie ot culture-yields tubers, very many of which weigh 3 lbs. and many attain to 



No. /.] OP MIXED MANURES. H 

this, though important to be made, should be tried cautiously, and on such a 
scale as to secure the experimenter from any serious loss. 

In the above suggestions I have introduced nothing in regard to mixed ma- 
nures — though where plants require for the supply of all their wants nine or 
ten different ingredients, of which the soil they grow in can perhaps yield in 
sufficient quantity only three or four, it is obvious that the very best conse- 
quences may follow from the employment of mixed manures. To this class 
belong common night-soil, urine, animalised carbon, poudrette (night-soil mixed 
with lime and gypsvim), the poudre vcgetatif (a mixture of soot and saltpetre), 
the urate (now manufactured in London), and many others. 

The mode of preparing, and the special uses of these and other mixed ma- 
nures, will be explained in the third part of these lectures, which will be devoted 
to the consideration of the nature and uses, and to the theory of the action of 
natural and artificial fertilizers. In the mean time it is desirable, in the first 
place, to obtain results from which the special action of each, wherwised alo^ve, 
can be fairly deduced. 

That these experiments may have their full value, it is indispensable that a 
measured portion of each field should be left Mdthoutmanui"e or dressing of any 
kind, in order that a true idea may be formed of the exact effect of each sub- 
stance employed. Experiments are valuable to the practical man if they mere- 
ly show the superiority of one species of manure over another, but they are in- 
sufficient to show how much each of them tends to increase the produce — or to 
enable us to arrive at a satisfactory explanation of the mode in which they 
severally act in promoting vegetation. 

Among other important experiments lately published, to which the above ob- 
servation is applicable, may be mentioned those of Mr. T. Waite of Doncaster. 
The effects of nitrate of soda on his land were very striking, showing a remarkable 
increase of produce over bone dust, rape-dust, or rotten fold-yard manure — but 
he does not seem to have determined the prodijce of the same land during the 
same season and without manure. We have, therefore, no term of comparison, 
by means of which we can ascertain the absolute or even the exact comparative 
effect of the different substances employed. 

It has been well observed by Sir Humphry Davy, " that nothing is more 
wanting in agriculture than experiments in which all the circumstances are mi- 
nutely and scientifically detailed, and that this art will advance in proportion as 
it becomes exa<;t in its methods."* The above suggestions are submitted to 
practical men in the hope that they may assist in introducing such exact meth- 
ods into om- agricultural operations, and at the sanne time promote the theoreti- 
cal advancement of the most important art of life. 

Exact methods lead to theoretical discoveries, while these are no less certain- 
ly followed by important practical improvements. 



No. 11. 

{^See Lecture II., p. 37.) 

In illustration of the effect of sudden alternations of temperature on vegetable 
substances, explained in a note subjoined to page 37, I quote with pleasure the 

the weight of 5 lbs. When perfectly ripe, it is said to be an excellent table potatoe, and to be 
best in the spring. — Albany Cultivator, for March, 1841. 

* Agricultural Chemistry, Lecture I. 



12 ON SUDDEN ALTERNATIONS OP TEMPERATURE. [Appendix, 

following instructive letter from an ably conducted monthly journal published 
at Albany, in the State of New- York, under the title of the Cultivator. It is 
extracted from the Number for March last : — 

" In regard to Irish potatoes, a still thinner covering of earth than the one 
just mentioned suffices with us to preserve them from rotting. Indeed, it would 
seem as if they could freeze and thaw several times, during winter, without 
being destroyed, provided they are covered with earth all the time ; for we often 
find them near the surface and perfectly sound, in the spring, when spading up 
the gi'ound in which the crop had grown during the previous season. There 
they must have undergone freezing and thawing whenever the earth was in 
either state, as it often is to a much greater depth than the potatoe roots ever 
extend. Why should those roots always be destroyed when they freeze above 
ground, and not suifer equally when frozen under ground ? 

" The reason why potatoes, apples, &;c. become soft, and rot when frozen 
and then thawed suddenly, uncovered and in open air, is the sudden thawing. 
You may put a heap of apples on the floor of a room, or other dry place, where 
they will freeze perfectly hard, and if covered close with any thing that will ex- 
clude the air, when the weather becomes warm enough to thaw, the apples will 
remain sound and uninjured, after they are thus closely thawed. The cover 
may be of the coarse tow of flax, or any article that will cover them close and 
exclude the air. So apples may be packed in a tight barrel, if full and headed 
up so as to exclude the air. They may be suffered to remain so in a garret, or 
any dry place where it freezes hard, and they will be found sound and free from 
injury, if the baiTel remains tight till they are thoroughly thawed. It is the sud- 
den thawing that causes the apples or other vegetables to become soft and rot. 

" So if the fingers on your hand be frozen, and you expose them to sudden 
heat by warming them at the fire and they suddenly thaw, the flesh will morti- 
fy and slough off. But, if you freeze your fingers or other limbs, and put them 
in snow, and rub gently till they.thaw, — or if put into a pail of water just drawn 
from the well, which will be less cold than your frozen fingers, — they will thaw 
slowly, and suffer but little injury. 

" So during the early autunmal frosts in September, if the morning after the 
frost is cloudy, the frost will be slowly drawn from the frozen vegetables, and 
they will be uninjured ; but if they receive the rays of the early and clear sun, 
they thaw so suddenly, that they will hang their heads and perish. If wet with 
water from the well, long enough to extract the frost before the sun shines on 
them, they do not suffer. 

" Onions are a difficult root to keep in winter. If they are put in a cellar 
warm enough to save them from frost, they will vegetate and be deteriorated. I 
put them in the warehouse, where they freeze as hard as if out of doors. If in 
a heap, I cover them close with some old clothes, or any thing that covers close, 
to exclude the air. The same if in boxes or casks. They freeze hai-d, but it 
does not appear to injure them for present use, if thawed by putting them into 
a pail of fresh-drawn water, to draw out the frost just before cooking them. 
Onions, thus kept, will be in good condition in the spring, after thawing under 
cover from the air. 

" I put parsneps, carrots, beets, &c., in boxes or casks, and then cover them 
with potatoes, which preserves them from drying." 

In further illustration of this subject I need only recall to the recollection of 
the gardener the well known fact, that, when the winter frosts begin to set in, 
and his finest flowers to be nipped, those continue to blow the longest, on which 
the sun's rays fall latest in the day. Dahlias protected in this way, will bloom 
occasionally for weeks, after those which regard the eastern sky are completely 
withered. 

Professor Lindley has published a series of valuable observations on the effects 
of extreme cold upon plants. The general results of these observations are 
stated in his ^'■Theory of Horticulture^^ p. 88. But the conclusions at which 



No. //.] ON SUDDEN ALTERNATIONS OF TEMPERATURE, 13 

he has arrived are deduced from the appearance presented by the plant after it 
was thawed. He found the tissue more or less lacerated, the contents of the air 
and sap vessels intermingled, and the colouring matter and other secretions de- 
composed. He attributes the laceration to the freezing and consequent expan- 
sion of the juices, but this cannot be the necessary consequence of that freezing, 
since it does not appear, if the whole tuber or leaf be slowly thawed. I would 
explain the phenomena as follows : — 

1°, When the leaf, fruit, or tuber freezes, the fluid portions slightly expand 
in becoming solid, but the air in the air vessels contracts in at least an equal de- 
gree, and thus allows a lateral expansion of the sap vessels sufficient to prevent 
lesion. When the temperature is slightly raised, the air expands but slightly, 
and ice is melted long before the gaseous substances reach their original bulk. 

2°. But if the rays of the sun strike suddenly upon the leaf or fruit, the sur- 
face may at once be raised in temperature 30° or 40° F. The air will conse- 
quently expand suddenly, and before the sap is thawed may have distended and 
torn the vessels, and caused sap and air to be mutually intermingled. ^ 

3°. But the moment the sun's rays strike upon the green leaf, its chemical 
functions commence. It begins to absorb and decompose carbonic acid : and 
as in the frozen part of the leaf the circulation is not, and in consequence of the 
lesion cannot be, established, the chemical action of the sun's rays must be ex- 
pended upon the stagnant sap ; and hence those changes not only in the sap 
Itself, but even in the solid parts, which are seen to take place in the withered 
leaf 

4°. Though not in a state of growth, the tuber of the potatoe contains the 
living principle, and there must be such a circulation going on in its interior as 
to maintain an approximate equilibrium of temperature throughout its sub- 
stance. A sudden thawing of the exterior, will, as in the leaf, expand the air 
before the circulation can be established throughout the frozen mass. The solid, 
fluid, and aeriform substances which nature has separated and set apart from 
each other, will thus all be intermingled, and from their mutual action, those 
chemical changes of which we know the starch of the potatoe to be susceptible, 
will speedily ensue ; — in other words, the potatoe will rot. 

The practical applications of these views are numerous. If a sudden frost 
come on, — protect your delicate flowers in the early morning from the i-ays of 
the approaching sun, and cover with straw or earth the potatoes which have 
been left overnight in the field. 



No. III. 

RESULTS OF EXPERIMENTS ON PRACTICAL AGRICULTURE DURING 
THE SPRING AND SUMMER OF 1841. 

{See Appendix, No. 1,, and Lectures VIII. and IX.) 

In a previous article inserted in this Appendix, and which was published 
early in the present spring (April, 1841,) I ventured to offer to the practical ag- 
riculturist some suggestions in regard to the experimental tise of certain un- 
mixed manures. From the results of these experiments, which I was quite sure 
some of the many zealous agriculturists of the day would be induced to under- 
take after the manner, and with the precautions, I had pointed out, I anticipated 



14 



RESULTS OF KXPKRIMENTS ON PRACTICAL AGRICULTURE. [Appendix^ 



a two-fold advantage. In the first place, that important practical benefits to 
the agriculture of certain districts would be derived from tliem, and secondly, 
that interesting and important light would be thrown by them on many parts 
of agricultural theory. It is by experiment that all the remarkable results — 
theoretical as well as practical — of modern chemistry have been arrived at ; 
but by experiments cautiously made, frequently repeated, and logically reason- 
ed from. The proceedings of the practical farmer are a continued course of ex- 
perimental trials, and to convert liim into an experimental philosophei', and to 
lead him to philosophical results, it is necessary only that his experiments 
should be made ivitJi a constant reference to weight and VLeasure, and should be 
repeated Knder varied and carefully noted conditions — and that he should be 
taught to draw from them no conclusions more general than they really 
justify. 

The following results of experiments made during the past summer confirm 
all my anticipations. Though necessarily somewhat limited, and local in their 
nature, they, nevertheless, present on the whole a beautiful illustration of what 
we have yet to expect from a continuation of such experimental researches, con- 
ducted in so skilful a manner. I need not especially commend the experiments 
of Mr. Fleming : for 1 can scarcely, 1 think, render a better service to practical 
agriculture than by placing all of them in the hands of practical men, and ear- 
nestly commending them to their careful consideration and imitation. 

I. Experiments made near Aske Hall, on the property of the Earl of Zet- 
land, on lots of half an acre each. 



1. Soot — piLt on May 24 — 10 bushels cost &s, 6d. 
Weight of grass when mown. 3 tons 16 cwt. 
Weight when made into hay, 1 " 15 " 



2. Salt — -put on May 24 — 3 bushels cost 6s. &d. 
Weight of grass when mown, 3 tons 19 cwt. 
Weight when made into hay, 1 " 16 " 



3. No Manure. 

Weight of grass when mown, 3 tons 12 cwt. 

Weight when made into hay, 1 " 6 " 



Nitrate of Soda — put on May 24 — 4 sto7ies 
cost lis. 
Weight of grass when mown, 4 tons 10 cwt 
Weight when made into hay, 1 -' 12 " 



5. S^dphate of Soda {in crystaUy-^pvi, on May 

24 — 4 stones cost 10s. 
Weight of grass when mown, 3 tons 3 cwt. 
Weight when made into hay, 1 " 9 " 



Sulphuric Acid — ^ put on May 26, \ put on 
June 7, ^ put on June 11 — \blbs. cost 5s. 

Weight of grass when mown, 3 tons 4 cwt. 

Weight when made into hay, 1 *' 6 " 



Q? 



iiJ 



c .5 



2 = 



■go 00 CQ too I 
I— OOOO I 



CQ CC to «5 O X> 
O O C^ Tl< -"^ CO 



•gc^O"<*c»c;jc5 



o CC CO CO C? (M CQ 






■^ "3 



■too O? O to 00 rft 

g T-H r-l 



w w » to w 
CO CO CQ O ITS 
.-I l-H C^C* 



CO 003 OJ O 

oj f-t — CO 



' (U es S ^ 



CZ3 
O 

S 



N. B. The cost of the manure does not include the expense of laying it on. 



No. III.] RESULTS OP EXPERIMENTS ON PRi^CTICAL AGRICULTURE. 15 

Mr. Turner, his lordship's agent, thus writes : — 

'* The plan I followed in putting on the different manures, and the quantities 
used, accorded as nearly as 1 could manage it, with the directions given in your 
published lectures. 

" The field on which the experiments were tried is situate in a high, bleak 
climate, and consists of a thin light soil, upon a bad subsoil of barren clay 
resting upon limestone. It had been completely exhausted by a succession of 
white crops, and was full of weeds and quickens. I had it well ploughed, and 
took a crop of drilled turnips fairly, but not extravagantly, manured. The crop 
was a poor one. I ploughed the land as soon as the turnips could be got off. 
Drained it ; and in the spring worked it very fine. The following August I 
sowed it away with grass seeds without a crop. The seeds came up beautiful- 
ly, and were the admiration of all who saw them, keeping a deep green through 
the winter, and beginning to grow early in the spring; and it was on this crop 
that the experiment was tried early in the succeeding summei*. 

" I need scarcely remark, that the ci'op of grass for such land was enormous, 
and has fully repaid the money expended upon it, with the exception of drain- 
ing, and in two or three years I have no doubt but it will repay this also," 

Remarks. — On comparing the effect of these several top-dressings as indi- 
cated by the results above stated, the reader will be struck with the extraordi- 
nary increase caused by the addition of common salt. I have in the text 
(Lecture IX., p. 190,) indicated a principle which may serve to explain in some 
measure both the localities in which the use of common salt may be expected 
to be beneficial, and the reason why in many parts of our island the employ- 
ment of this substance has not been attended by any large measure of success. 
The position of the land experimented upon by Mr. Turner, is such as to lead 
us to expect it to be improved by common salt, according to the views there 
stated. 

The nitrate of soda produced less effect .than either the common salt or the 
soot, but it gave an increase w^hich was double of that yielded by the sulphate 
of soda. The latter salt, however, was appHed in the state of crystals, which 
contain 55 per cent, of water, so that less than one half of that weight of dry 
salt was used, which was recommended in the suggestions 1 offered for the 
employment of this substance in practical agriculture. At the same time, the 
price paid by Mr. Turner for this salt was /^^r times as great as it ought to 
have been. Any quantity of the o'ry sulphate of soda may be procured at lOs. 
a cwt., at which price it is forwarded in casks to all parts of the country by 
Messrs, Allan & Co., Heworth Alkali Works, Newcastle, 

The most valuable practical suggestion to be derived from these experiments 
is certainly this— that a liberal use of common salt is likely to increase in a great 
degree the produce of grass in the locality where they were made, and on the 
same kind of soil. This valuable discovery will far more than repay the ex- 
pense and trouble of the entire series of experiments. No application can be 
so cheap as this, so long as it succeeds. At the same time a mixture of the other 
substances— the nitrate and the siUphate, which were partially successful— might 
possibly prove still more efficacious on the grass, and might be expected even 
to ameliorate the condition of the land for the further production of white crops. 
In a future part of this Appendix I intend to oflfer some suggestions in regard to 
the ki7id and quantity of the ingredients which may, with probable advantage, 
enter into the constitution of these 7nixed mamtres. 

I have calculated and introduced into Mr, Turner's table an additional col- 
umn, exhibiting the weight of hay yielded by 100 lbs. of grass, whh the view 
of showing the relative succulence of the several crops when cut. As a gen- 
eral rule, the weight of dry hay does not exceed one-fourth of the weight of the 
grass when cut. In the experiments of Mr, Turner, however, the weight of 
hay in every case was much beyond tliis quantity — the most succulent crop, 
that to which no dressing was applied, yielding 36 per cent, of hay. This gen- 



IG RESULTS OP EXPKRIMENTS ON PRACTICAL AGRICULTURE. [Appendix. 

eral result may have been partly due to the state of ripeness in which all the 
grasses were cut, while the greater produce of hay from the dressed portions 
may indicate the relative ripeness, and therefore dryness, of each when cut down. 

It is evident, therefore, that the relative values of crops of grass or clover are 
not to be judged of by the several weights when green, but by the weights of 
the diy hay. This is further confirmed by the results of an experiment with 
nitrate of soda, communicated to me by Mr. Cai'iiithers, of Warmonbie, near 
Annan, in which the relative weights of hay obtained were much riwre in favour 
of the use of the nitrate than the several weights of grass yielded by the dressed 
and undressed portions of the field. On the contrary, from a field on Oliver 
Farm, near Richmond, Mr. Sivers informs me, that the weight of hay was7?mcA 
less in favour* of the use of the nitrate of soda than the relative weights of 
grass. In all cases, therefore, the weight of the dry crops obtained by different 
methods should be compared with each other, as the safest test of the relative 
merits of the several modes of procedure by which they have respectively been 
raised. 

II. Experiments made at Erskine, on the property of Lord Blantyre. 

I insert the clear and well-digested statement of his Lordship's agent without 
alteration: — 

" Freeland, Erskine, by Old Kilpatrick, Glasgow, 2dlh July, 1841. 

" Sir — Agreeably to Lord Blantyre's instructions I send you a copy of the re- 
sults of some experiments with manures on young grass for hay, undeilaken 
on two separate pieces of land — the one a very good light soil (subsoil gravel) ; 
the other stiff clay soil with a clay subsoil. The manures were applied on 1st 
May, the hay cue on the 1st and weighed on the 19th July current; the extent 
of each plot one-twentieth of an imperial acre. From the small extent of each plot 
it will be evident that the results cannot be exactly depended on, farther than as 
a general result ; because in so small a portion of land the least variation in the 
soil or crop naturally will affect the results very materially ; still, on the whole, 
I am of opinion that the experiment gives the compaj'ative view of the value of 
the different manures used pretty nearly. 

" One thing has astonished us with regard to soda (nitrate). On all the fields 
I have observed it sown on, the part dressed has a much greater vigour of after- 
math than where no nitrate of soda was given : showing that this manure is not 
so evanescent as was generally supposed. 

" I am, Sir, your most obedient servant, 

"Jas. Wilson." 

Experiments loith Manures as a top-dres^ng for Hay, at Erskine, 1841. 

Remarks. — It will be observed in these experiments, that the saltpetre and 
nitrate of soda produced nearly an equal increase on both kinds of soil, the ni- 
trate of soda having the gx-eater effect on the light, the nitrate of potash on the 
heavy soil. Next to these on the light soil are the common salt and sulphate of 
soda, though on the heavy soil the common salt had the better effect of the two. 
It is to be observed, however, that in this case the sulphate was used in crystals, 
and therefore only in half the quantity recommended. Had twice the quantity 
been employed vipon the llg/d soil the produce might have equalled that from the 
nitrates. 

It is a singular illustration, however, of the necessity of applying different 
substances to different soils — that so far as this experiment is to be depended 
upon, the sulphate of soda almost entirely failed on the heavy land. 

The most valuable practical deduction from these experiments also, is, that 
on both the soils in question, the grass land, in ils present condition, may be salted 
to advantage. At the same time, it appears probable that on the light soil the 
increased produce would amply repay the cost of applying either nitrate or sul- 

' In Rfr. Sivers' experlment.s, 100 square yards, nitrated, gave 68 stones of hay, unnitrated 
52 stones, but when dry they were reduced to 12 stones each. How very much more suc- 
culent these grasses were than those of Mr. Turner ! 



No. HI] 



ON MANURE AS A TOP-DRESSING FOR HAY. 



17 



phate of soda at the rate of 120 lbs. per acre— the latter being in its dry or un- 
crystallized state. 

The effect, generally, of all the diessings is strikingly greater on the light 
soil — a fact which speaks strongly in favour of the adoption of any of those 
methods by which the openness and friability of the land has been found to be 
permanently promoted. On the stiff soil, even the ammonia, by some deemed 
so vitally necessary to vegetation, appears to have produced no sensible alter- 
ation. 







0. ^' 


■ 




I 




i 




Manures used, and quantities applied, to 


■§8^ 


CO .C 


Total produce 


Total additional 


i2 

Q 


each plot of l-20th of an acre. 


■S£ 


^■z 




per 


weight per 


P^ 




^.S 


1^ 


Imperial Acre. 


Imperial Acre. 


Exp. I. Good light soil, subsoil gravel. 


ts. 


cwt. 


qrs. lbs. 


ts. cwt. 


qrs. lbs. 


1 


1 lb. sulphuric acid, diluted in 47 ) 
galls, water . . . \ 


271 


44 


2 


8 


1 16 


- 7 


3 12 


2 


6 lbs. saltpetre (nitrate of potash) 


322 


95 


2 


17 


2 


- 16 


3 24 


3 


6 lbs. nitrate of soda . 


339 


112 


3 





2 4 


1 





4 


6 lbs. sulphate of soda (in crystals) 


292 


65 


2 


12 


16 


- 11 


2 12 


5 


17 lbs. gypsum .... 


254 


27 


2 


5 


1 12 


- 4 


3 8 


6 


1 bush, wood charcoal (pounded) 


277 


50 


2 


9 


1 24 


- 8 


3 20 


7 


\ bush, common salt, 25 galls, water 


294 


67 


2 


12 


2 


- 11 


3 24 


s 


1 gal. amnion iacal liquor, 47 gls. water 


277 


50 


2 


9 


1 24 


- 8 


3 20 


9 


No application .... 
Exp. II. Clay sail, subsoil clay. 


227 




2 





2 4 






1 


1 lb. sulphuric acid, diluted in 47 ) 
galls, water . . . ) 
6 lbs. saltpetre (nitrate of potash) 


256 


26 


2 


5 


224 


- 4 


2 16 


2 


286 


56 


2 


11 


8 


- 10 





3 


6 lbs. nitrate of soda . 


282 


52 


1 


10 


1 12 


- 9 


1 4 


4 


6 lbs. sulphate of soda (in crystals) 


232 


2 


2 


1 


1 20 


- 


1 12 


5 


17 lbs. gypsum .... 


240 


10 


2 


2 


3 12 


- 1 


3 4 


6 


1 bush, wood charcoal (pounded) 


257 


27 


2 


5 


3 16 


- 4 


3 8 


7 


1 bush, common salt, 25 galls, water 


269 


39 


2 


8 


4 


- 6 


3 24 


i B 


1 gal. ammoniacal hquor, 47gls.water 


201 


— 


1 


15 


3 16 


- - 


- - 


9 


No application .... 


230 


— 


2 


1 


8 


- - 


- - 



The Dressings were applied 1st May, the Grass cut 1st July, and the Hay 
weighed 19th July. 

III. Experiments made under the immediate superintendence of W. Fleming, 
Esq., of Barochan, near Paisley, and on his own property. The statement is 
drawn up by Mr. Fleming himself. 

1. — Experiments on Hay with Nitrate and Sulphate of Soda and with Gypsum^ 







Description of 


Rate per 


Weight per 


Weight 


No. 


Field. 


Dressing. 


imp. Rood 


Rood, green. 


when stack'd 


1 


Covenlea. 


Nothing. 





, 3361 lbs. 


1120 lbs. 


2 


Do. 


Nitrate of Soda. 


40 lbs. 


4907 " 


1636 " 


3 


Do. 


Sulphate of Soda. 


40 lbs. 


3966 " 


1322 " 


4 


Do. 


Gypsum. 


10 lbs. 


3831 " 


1277 " 


1 


Crook's High 


Nothing. 


— 


4436 " 


1478 " 


2 


Do. 


Nitrate of Soda. 


40 lbs. 


4999 " 


1666 " 


1 


Crook's Low. 


Nothing. 


— 


2185 " 


728 " 


2 


Do. 


Nitrate of Soda. 


40 lbs. 


3764 " 


1254 " 


3 


Do. 


Gypsum. 


80 lbs. 


3110 " 


1036 " 



18 



EXPERIMENTS ON WINTER RYE. 



[Appendix, 



Character of the Soil — Nos. 1, 2, 3, and 4 were good sharp soil, on rotten 
rock, (decayed trap,) all as near as possible the same description of land, 
drained, and lying together. Nos. 1 and 2, Crook's High, stiff clay, drained; 
the hay was after wheat. Nos. 1, 2, and 3, Crook's Low, light clay-loam, 
drained ; the hay was after barley. 

On Covenlea the dressings were applied on the 22nd of April, and the hay cut 
on the 2nd of July ; on the other fields the nitrate and gypsum were applied on 
the 12th of April, and the hay cut on the 9th of July. 

N. B. The above is the average of trials in three parts of the Covenlea field; 
a small portion of moss was also sown with nitrate of soda, in the low part of 
the same field, but no benefit was observable, beyond the usual dark green 
colour which appeared about ten days after the application. The sulphate of 
soda, although evidently beneficial, does not produce the dark green colour. In 
the Crook's fields the effect of nitrate of soda in producing the dark green colour 
was as remarkable as in the Covenlea field. The gypsum on both fields seems 
to have had a good effect, particularly on the aftermath clover. 

Rrmarks, — In these experiments also the sulphate of soda was used in only 
half the quantity recommended. By referring to the prices paid by Mr. Fleming, 
it will appear that the use of sulphate of soda gave an increase of 200 lbs. of 
hay for Is. 9d. (or 500 lbs. for 4s. 5d.), while the niti-ate of soda gave an increase 
of 516 lbs. for 7s. lOd. ; so that, though the actual increase of hay per rood was 
considerably less by the use of the sulphate, yet that increase was obtained at 
little more than half the cost of the same weight of increase derived from the ni- 
trate. A similar remark applies to the gypsum, so that these experiments give 
ample encouragement for the application of both these substances in sojuewhat 
lax'ge quantity to succeeding crops, on the same land. 

2. — Experiments on Winter Rye, dressed with Nitrate of Soda, Lime loith Potash, 
Sulphate of Soda, and Muriate of Ammonia {Sal Ammoniac.') 









Rate per 


Weight of 


Weight of 


Bushels 


No. 


Field. 


Description of 


rood 


Grain. 


Straw 


per 


I 




Dressing. 


imperial. 


per rood. 


per rood. 


rood. 


Garden Plot. 


Nothing. 





160 lbs. 


1024 lbs. 


3i 


2 


Do. 


Nitrate of Soda. 


40 lbs. 


336 " 


1664 «' 


6^ 


3 


Do. 


Lime and Potash. 


40 " 


272 " 


1344 " 


5i 


4 


Do. 


Sulphate of Soda. 


40 '' 


224 " 


1152 '« 


4i 


5 


Do. 


Mur. of Ammonia 


5 " 


232 " 


1216 " 


4f 



Character of the Soil. — Tilly clay, which had been trenched, and in potatoes 
the year before. The Pi.ye was sown on their being lifted in October, 1840. 

The applications were made on the 14th of April, the grain was cut on the 
9th of August, and thrashed on the 25th. 

N. B. As early as the end of April the effects of the nitrate of soda were very 
apparent from the dark green colour produced, and broadleaves, and after it was 
ripe the heads were longer than any of the others ; but it was so strong that it 
was laid a month before it was cut ; none of the others were laid. Every ap- 
plication seems to have done good, by increasing the produce. The potash and 
lime was made by slaking quick-lime and sand with a solution of potash, and 
allowing them to lie together for a month. As much was used as contained 1 
lb. of carbonate of potash to the pole. 

Remarks. — From these experiments, it appears that, besides the proportionate 
increase of straw, that of grain was 

From nitrate of soda, 12 bushels for 31s. Od., 
" lime and potash, 7 " for 33s. 6d., 
" sulphate of soda, 3 " for 7s, Od., 
•' sal-ammoniac, 5 " for lOs, 9d., 



or 2s. 9d. per bush, 
or 4s. 9d. " 
or 2s. 4d. " 
or 2s, 2d. " 



No. Ill] 



EXPERIMENTS ON WHEAT FIELD. 



19 



Although, therefore, the total increase by the employment of sulphate of soda 
and muriate of ammonia, in the proportions actually put on, was not so gi-eat as 
by the use of the other two dressings, yet this increase was obtained at a con- 
siderably less cost per bushel. The lime and potash, though producing an im- 
portant effect, will probably not yield a remunerating return with this crop 07i 
this soil, while the results hold out a fair inducement for the trial of the last two 
dressings in larger and varied proportions. 

The five samples weighed respectively,— 45 3-5, 51 3-4, 51 4-5, 52 3-5, and 
48 4-5 lbs. per bushel, so that, while on all the dressed plots the grain was 
heavier than on the undressed, that which was dressed with sulphate of soda 
was considerably the heaviest, 

3. — Experiments on Wheat Jleld, CrooK's {crop^ 1841.) 



No. 

1 

2 

3 
4 
5 

6 

7 



Description 
of Top-dressing. 



Nitrate of Soda. 

Potash 

and Lime. 

Common Salt. 

Mur. Ammonia. 

Nitrate of Soda 

and Gypsum. 

Nitrate" of Soda 

and Rape-dust. 

Mur. Animoma 

and Lime. 

Common Salt 

and Lime. 

Nothing;. 



Rate per 
Scotch acre. 



I GO lbs. 
160 lbs. \ 

40 bush. \ 
160 lbs. 

20 lbs. 

80 lbs. \ 
160 bush. S 

80 lbs. 
5 cwt. 

20 lbs. 

40 bush. 

28 lbs. 

80 bush. 



Weight of Weight 



produce of 
Grain of 

.'fith acre. 



of 
Grain 



Weight of to- 
tal produce, 
ichen cut, of 



pr. bshl. /8 th an acre. 



209 lbs. 

210 " 

249 " 

208 " 

214 " 

240 " 

230 " 

200 " 
190 " 



163 lbs. 

j62 " 

62 " 
!62 " 

62 '' 
62i" 

63 " 

63i" 
61 " 



9,500 lbs. 

8,930 '' 

12,540 " 
8,360 " 

8,620 " 

11,970 '' 

9,500 " 

8,740 " 
8,050 " 



Character of the Soil— The land was a heavy loam, and of as nearly as pos- 
sible the same quaUty. It had been in potatoes, and the wheat was sown when 
they were lifted in October, 1840. 

The applications were all made on the 13th of April, and the crop was reaped 
on the 2d of September. 

The produce of Ith of a Scotch acre, thrashed and weighed and well cleaned, 
gave an average of from 32 to 33 bushels of 61 lbs. each per Scotch acre of grain. 

Remarks.— This table presents us with two remarkable results,— that ob- 
tained by the use of common salt, and that from a mixture of soda and rape- 
dust. Thus, exclusive of the straw, — r. r.j i i i 

Nitrate of soda alone gave 152 lbs. of wheat for 31s., or l2s. 2d. per bushel; 

Nitrate with rape-dust ffave 400 lbs. of wheat for 43s. 6d., or 6s. 9d. per bushel ; 

Common salt gave 472^1bs. of wheat for 3s. 6d., or 6d. per bushel. 

The increased produce, by the use of common salt, is by far the most valua- 
ble result to Mr. Fleming in an economical point of view, and plainly indicates 
the kind of application he can most profitably make— to his wheat crops at least— 
on land similar to the above, and in the district where he resides. 

Neither the nitrate of soda nor the mixture of this salt with rape-dust, gave 
such an increase as to repay their own cost, unless when corn is very high. It 
is interesting, however, to observe that the mixture with rape-dust gave so large 
an increase, though the value of this particular experiment is lessened by the ab- 
sence of any trial with rape-dust alone, by which the effect of each of the ingre- 
dients ought to be judged of. I have reckoned the rape-dust at £1 a ton, so that 
5 cwt. would cost 28s., and we know that a top-dressing of this substance alone, 
in a somewhat larger quantity, gives a remunerating return in many of our wheat 
lands. 



^ 



EXPERIMENTS ON EARLY POTATOES. 



[Appendix, 



Mr. Outhwaite, of Banesse, in the North Riding of Yorkshire, a skilful and 
enterprising practical farmer, who has for some years been using rape-dust over 
a great breadth of his M-heat crop, has favoured me with tlie result of one of his 
more accurate trials on spring wheat, made during the past season. The wheat 
was sown after turnips taken off in April, and part of the field was dressed with 
rape-dust at the rate of 5| cwt. (or at £1 a ton, of 40s.) per acre. The produce 
of the dusted portion was 39 bushels, and of the undusted 29 bushels per acre, 
and the increase of straw was one-fifth of the whole. Both samples were of 
equal weight, and sold at the same price, — 8s. 3d. per bushel. In this experi- 
ment the increased 10 bushels cost 40s., or 4s. per bushel, giving, on a large 
breadth of land, a handsome remuneration. 

These results will, I trust, encourage others to make trials similar to those of 
Mr. Fleming and Mr. Outhwaite ; while these gentlemen will, doubtless, be in- 
duced each to try that application which has succeeded so well in the other's 
hands. It might be useful as well as interesting to compare the produce of four 
plots arranged and dressed as follows : — 



Common Salt. 


Rape- dust. 


Common Salt 
and Rape-dust. 


Nothing. 



4. — Experiments on Early Polatnes, 1841, 
All were dunged in the usual manner with farm-yard manure, at the rate of 
about 30 cubic yards per acre. The potatoes were all planted on the 25th of 
March, on the same heavy black soil. The several dressings were applied on 
the 20th of May, and the potatoes were all lifted on the 28th of September. 



^ 



Description 

of 
Top-dressing. 



Rate 

per imp. 

acre. 



1 Nothing. 

2 Nitrate of Soda. ]l60 lbs. 
3{Sulphate of Soda. 200 " 

4 Do. & Nitr.of Soda'200 " 



Produce 
per imp. 



m bolls. 
80 " 
73 " 
107 " 



Weight of 

Produce of 

18 yards drill. 



77 lbs. 
93 " 
86 " 
124 " 



Note.—TYiQ 
peck is 35 lbs. 
weight, and 16 
make a boll 
or 5 cwt. 



This break of ground consists of a piece of poor clay mixed with moss, about 
9 inches deep ; subsoil a very stiff blue till. The dung was old from the farm-yard, 
aboiit the ordinaiy quantity (30 cubic yards per acre) spread upon the land, and 
dug in. The potatoes were drilled in with the hoe; as the ground was wet the 
plants came up but weak. The nitrate of soda was sown before the other top- 
dressings, and had remarkably quick eflfect, as it showed the third night after 
being sown. The sulphate of soda does not occasion the dark green colour 
which is seen upon the potatoes after the dressing of the nitrate, but there is not 
the smallest doubt of its beneficial effects, although not in so great a degree as 
the nitrate. The mixture, which is composed of'fds of sulphate of soda and H 
of nitrate, has a wonderful effect in strengthening the growth (which it keeps 
longer than with nitrate alone), and the mixture has the same effect in producing 
the dark green colour as the nitrate alone. 

Remarks.— That a mixture of substances is likely to be more eflicacious as a 
dressing, than the application of one substance alone, except in peculiar circum- 
stances, is consistent not only with long practical experience— for how many 
substances are mixed together in farm-yard manure '?— but also with the theore- 
tical principles laid down in the text. [See Lectures IX. and X.] These experi- 
ments upon potatoes show that this crop upon Mr. Fleming's land was benefitted 
by both nitrate and sulphate of soda, but in a vastly greater degree by a mixture 
of the two. And I might consider my suggestion in regard to the employment 
of sulphate of soda as a manure, to have been of no mean use in practical agri- 
culture, had it led to nothing else than to this happy mixture of Mr.Flemin"-. 

I have received also from Mr. Fleming's gardener(Mr. Alexander Gardiner) 



No. III.] EXPERIMENTS ON EARLY POTATOES. 21 

a very well digested and well drawn up paper, detailing numerous experiments 
made by himself during the past summer. Among these is one upon the use of 
this same mixture upon thepotatoe crop, which I shall quote in his own words: 

"April 26th. — Planted potatoes of the red Don variety, soil a mellow loam, 
two feet deep, subsoil yellow till. Farm-yard dung was trenched in some days 
before planting, at the rate of 40 cubic yards per acre ; sets drilled in with the 
hoe. Plants came up very regular, and were top-dressed with a mixture of f 
sulphate and ^ nitrate of soda on June 2nd, at the rate of 2 cwt. per acre. They 
grew very strong after this application. Stems six or seven feet in length, dark 
gi-een, and the produce, when lifted in October, was 16 Renfrewshire pecks of 35 
lbs. each per Scotch fall of potatoes fit for market." 

This produce is equal, I believe, to about 26 tons per Scotch, or 21 tons per 
imperial acre, about equal to that of Mr. Fleming with the same mixture. And 
what an amazing luxuriance of vegetation, to yield at once stems seven feet in 
length and upwards of 20 tons of tubers per acre ! 

Those who are the most sceptical in regard to the benefits to be derived from 
agricultural experiments, when well conducted, will scarcely question the impor- 
tance of this result — the most backward in making experiments will be anxious 
to repeat this upon his own potatoes. The cost of the mixture to be applied in 

the quantity used by Mr. Fleming is as follows : — 

s. d. 

o 1 1 ^ CO J < 75 lbs. r?rv at 10s. per cwt. or ) n q 

Sulphate of Soda { 150 lbs. in crystals at 5s. . \ ^ ^ 

Nitrate of Soda . . 75 lbs. at 22s 14 9 

21 6 

The return for this 21s. 6d. was in each of the above cases upwards of 8 tons 
of potatoes. 

I may here mention also two other interesting experiments of Mr. Gardiner, 
in which he tried the effect of sal-ammoniac upon his potatoe crop, — 

1°. In the one he mixed sal-ammoniac, previously dissolved in water, in the 
proportion of 1 lb. to each cubic yard of a compost formed from the refuse of the 
garden, and planted early potatoes with it at the rate of 35 cubic yards per acre. 
The produce was one-sixth more than when no ammonia was used. The va- 
riety of potatoe was Taylor's forty-fold, the soil moss and clay. The cost of 
this application was 19s. per acre. 

2°. Sal-ammoniac, dissolved in water, was sprinkled on moss or peat earth, 
at the rate of 20 lbs. to a ton of earth, and, after strewing a little Ume at the bot- 
tom of the drills, this mixture was put in at the rate of 2 tons per acre. The po- 
tatoes were 14 days later in coming through the ground than the same variety 
planted with farm-yard manure. They were strong in the stem, of a dark green 
colour, and equal, hi point of produce, to the others. The variety of potatoe 
was the Irish apple, the soil a very light brown loam, of that description locally 
named deaf. 

I may observe on this latter experiment, that the application is not so simple 
as it appears. The lime would decompose the sal-ammoniac, and form chloride 
of calcium., while ammonia would be liberated. The effect, therefore, may be 
partially due to both. It will be recollected that in a previous part of this Ap- 
pendix I suggested the trial of this chlorftle of calcium as a top-dressing for va- 
rious crops. 

5. — Experiments on Moss Oats, sown about 1st May, 1841, top-dressed 25th June. 
" These top-dressings were applied on the 5th of June, and by the 24th there 
was a striking improvement, especially on No. 2 and No. 7. It was quite visi- 
ble in greater strength and evenness of crop. One or two of the others also 
showed improvement, but not so visibly as to merit particular notice. I exam- 
ined them from time to time, and at different dates : the appearances much the 
same as noticed upon June 24th. I again examined them a few days before 



^^ , iSXPERiMENT^ ON OATS. [Appendix, 

hones "being dWolved was a dra Jb^; J '""fi "'^'^^ ^^,S°od, but the want of the 
tlieexpense of another trial » ^'^'^^^'^- ^^oy^^y^r, I consider the two merit 



No. 



Top-dressing per pole (imperial). 



Nothing. 



Bones dissolved m sulphuric acid and nitrate of soda | lb 
Sulphate of soda i lb., bone dust i peck, 
t^otash 1 lb., lime and bone dust I peck. 
Chloride of calcium 1 lb., bones i peck. 

7 D ?®'uP°*?!'' ^""^ chloride of calcium, i lb. each. 
lit^otashandJime^iitrate, and bones, i lb. each 



gra?n (no^^^;^^^^^^^^^^ 4 feet to clay. No, 2 the best cro^Ii^heaviest 

Kr tS Nos 1 or C No fi ;hr'^ ^ ."°' '°u ^°°^^^ ^°- ^^ b"^ all much 
good-next to No 2 ^^- ^ ^^^^ ^^^'^t-not better than No. 1. No. 7 very 

most unfadmg remedy for this defect in the ear, as well as forTe le^s imDor^ant 



these suggestions IS seen m the above experiments of Mr. rfemn- T^^^^^^ 
a d" SluiaIl™SabIe1 h^'^ '^^ ^r.^ Fleming's united clSal llSg 
search No? 9 ^v^ ^° ^J"' ^l'*^ ^' -^''^^ ^'^^^l^s O'^ a new field of re- 

search, Nos. 2 and / may be considered as highly encouradn^ if not inrJppH 

our conclusions upon a larger experience. ' ^ ^ ^^ '^'^^^ 

e.-Experiments upon Oafs iop-dressc£wUk Sulphate mid Nitrate of Soda (lower 

end of Barn Park.) ^ 

"The first was sown on the 11th May, viz., 3 ridges with «;nlnh«f« ^r a 
at the rate of 1. cwt. per acre. This wJs exa;l;df L^teTj^IbutS 

is porous peat lands, he has fo.Zl i, n^.LL ?^ "' " l'^"''- '"/''''"■^ °?e that, in improving 



No. III.] EFFKCTS OF SULPHATK AND NITRATE OF SODA, 23 

appeared to be little, if any, difference from the general crop (it has not yet been 
thrashed.) Next, 3 ridges were sown with nitrate of soda, at the rate of 80 lbs. 
per acre. This made a little alteration both in colour and strength, but it was 
too little to make a very decided difference. Also, alongside of the last-men- 
tioned, a piece was dressed with a mixture of suiphate and nitrate of soda, in the 
f)roportion of f rds of the former to ^rd of the latter. This immediately took the 
ead of the others both in colour and strength, so much so, that by May 27th it 
could be seen from a distance. Many examinations were made of them all 
during the season, and this always appeared the best. A few days before it was 
cut, it showed the largest and best filled ear. There was a piece of yellow-col- 
oured earth at the bottom of the field, showing the presence of iron, upon which 
was sown potash and lime. The plant was yellow and sickly-looking, but im- 
mediately afler the application it acquired a dark green colour, and became vi- 
gorous, and yielded a crop at least equal to any in the field. There were some 
other dressings put on other ridges of this field, but it was dry weather directly 
afler they were sown, and the crop was too far forward before they began to take 
effect to say any thing decided about them. By mistake there were two varie- 
ties of oats sown upon the field, which prevented the experiments being so de- 
cided, as the dressings were put on indiscriminately upon the land before it was 
known." 

Remarks. — The only remark I need make upon these experiments is, to sug- 
gest to my readers that, by repeating the above trials upon oats with Mr. Flem- 
ing's mixtures, they may not only benefit their own crops, but may also aid 
materially in the advancement of practical agricultural knowledge. 

7. — On the effect of Sulphate of Soda applied as a top-dressing to Beans and Peas. 

" The first dressing was applied the 4th of May, on some beans on a border 
in the garden ; the drills that were dressed quickly took the lead of the others. 
There was no alteration of colour, but greater strengtli, and it tillered vxmder- 
fvMy. There were five or six stems from every seed sown, and the pods were 
larger and more numerous, and the beans in the pods a great deal larger than 
the same variety undressed. It was also put upon some of the ridges of the 
. beans in the field, and with the same effect, and gave a very large crop (not yet 
thrashed.) 

" Upon peas in the garden it appeared to add little, if any thing, to the strength 
of straw, but those that were dressed had a far greater number of pods, and those 
better filled, and the peas of a better flavour, and it seevis a valuable dressing for 
all leguminous crops. When sown in the drills along with the peas, it nearly 
killed every one of them, while the same quantity, put on as a top-dressing to 
some drills next to them (whei-e the peas were two inches high,) did no injury. 

Remarks. — The testimony of Mr. Fleming to the value of sulphate of soda 
as a dressing for leguminous crops, is very valuable and satisfactory. We may 
hope that next year will furnish us with experiments, all the results of which 
shall have been so carefully ascertained, as to enable us to decide upon the eco- 
nomical value of this sulphate as a manure, by a comparison of the amount of 
increase in the crop, with the cost of the application. 

8, — On Nitrate of Soda as a top-dressing to Gooseberry and Currant bushes. 

" It was applied April 14th, at about the rate of | cwt. per acre, or f lb. per 
bush. It had the effect, in the course of a week, of producing on the bushes a 
dark green colour and broader leaves, and the fruit set better and more plentiful- 
ly, especially on some red currants that had borne little for two years. These 
set their fruit well, and yielded double their former produce. The dressed bushes 
kept the lead in strength and vigour all the season, and now, when the undressed 
bushes have lost their leaves, the others are quite green." 

9. — " Many experiments were tried in the garden on turnips, by top-dressing 
with nitrate of soda, but with no perceptible effect. However, the Swedish, and 



24 ON EXPERIMENTS WITH GUANO. [Appendix 

red-top yellow, in a field of rather stiff soil, were benefitted, the former yielding 
i more produce in weight, and the latter ^ more weight. Wm. Fleming. 

"Barochan, 26th October, 1841." 

Note.— The prices paid by Mr. Fleming were as follow : — Bone dust (fine) la. 9d. per bushel ; 
sulphate of ammonia (in crystals) 283. per cwt. ; potash (very impure) 24s. per cwt. ; sulphate 
of soda (in crystals) 5s. per cwt. ; nitrate of soda 223. ; and sal-ammoniac 60s. per cwt. 



No. IV. 

SUGGESTIONS FOR COMPARATIVE EXPERIMENTS WITH GUANO 
AND OTHER MANURES. 

Guano is the name given in South America to the dung of the sea fowl which 
hover in countless flocks along the shores of the Pacific, and which, from time 
immemorial, have deposited their droppings on the rocks and the islands which 
are met with along the coast o^ Peru. 

Besides the fresh white guano which is deposited year by year in these locali- 
ties, there exist, in some spots, large accumulations more or less buried beneath 
a covering of drifted sand, which have been thus buried and partially preserved 
from an unknown antiquity. This ancient guano is of a brown colour, more or 
less dark, and forms layers or heaps of limited extent, but which ai'e said some- 
times to exceed even 60 feet in thickness. 

In the time of the Incas this substance was known and highlyvalued as a ma- 
nure, — the country along the coast for a length of 200 leagues was entirely ma- 
nured by it, — the islands on which it was formed were carefully watched and 
preserved, — and it was declared to be a capital offence to kill any of the seafowl 
by which it was deposited. Ever since that time it has been more or less em- 
ployed for the same purpose, and much of the culture now practised on this 
thinly-peopled coast is entirely dependent for its success, if not for its existence, 
on the stores of manure which the sea fowl thus place within reach of those parts 
of the country which are susceptible of cultivation. 

In modern times, however, the access of foreign shipping, and the want of 
careful protection, have driven away many of the sea fowl, and lessened to a very 
great degree the production of the recent guano. Thus tlie country is more de- 
pendent than in former times on the more ancient deposits, which are now assi- 
duously sought for, and when discovei-ed beneath the sand, are carefully exca- 
vated and transported to the sea-ports for sale. 

The dung of birds of all kinds, when exposed to the air, gradually undergoes 
decomposition, gives off ammonia, and acquires a brown colour. As this am- 
monia is one of the most fei-tilizing substances it contains, it will be readily un- 
derstood that the old brown guano is much less valuable as a manure than that 
which is recent and white ; hence the care of the ancient Peruvians in collect- 
ing the fresh, and their comparative neglect of the ancient guano. 

When the brown guano is put into water, a large quantity of it — sometimes 
70 per cent, of the whole — is dissolved. Hence, it is, becavise the climate of 
Peru is so dry and arid that in the plains rain scarcely ever falls, that the guano 
can accumulate as it is found to do. North and south of this line of coast, 
where rains are less unfrequent, such accumulations are not met with, though 
the birds appear equally plentiful, and it may be safely stated that, had the cli- 
mate of Peru been like that of England, the rains would have washed the guano 
from tlie rocks almost as rapidly as it was deposited. 

Of the brown guano several cargoes have lately been brought to England by 



No. IV.] ON EXPERIMENTS WITH GUANO. 25 

an enterprising merchant in Liverpool, and it has been deservedly recommend- 
ed to the attention of British agriculturists. It has already been tried upon va- 
rious crops, both of hay and corn, upon turnips also, and upon hops, and there 
can be no doubt whatever that in our cUmate, as well as in that of Peru, it is 
fitted to promote vegetation lo a very remarkable degree. 

This brown guano varies much in quality, according probably to the degree 
of exposure to the air to which it has been subjected, or to its position in the de- 
posit from which it has been dug. Two different portions, takea at random 
from the same box, gave me the following very different results : — 
1°. — Water, salts of ammonia, and organic matter, expelled 

by a red heat, 23-5 per ct. 

Sulphate of soda, ....... 1'8 " 

Common salt, with a little phosphate of soda, . . 30*3 " 
Phosphate of lime, with a little phosphate of magnesia 

and carbonate of lime, 44*4 " 

100* 

2°. — Ammonia, = 70 ^ 

Uric acid, =08 l59.3r,erct 

Water, carbonic and oxalic acids, &c,, expelled r '^ f 

by a red heat =51'5 J 

Common salt, with a little sulphate & phosphate of soda, 11 '4 " 
Phosphate of lime, &cc 293 " 

100 

According to M. Winterfeldt, this brown guano is sold at the ports near 
which it is obtained at about 3s. a cwt. It might, therefore, if this be correct, 
be imported into the country, and sold at less than lOs. per cwt. The price at 
present asked, however, is 25s. per cwt., a cost at which it is doubtful if the 
Ensrlish asrriculturist can afford to use it. 

In any case it seems improbable that the guano can continue to be imported 
into this country for any length of time. It is absolutely necessary to the cul- 
tivation of the land in Peru,— and it is also diminishing in quantity, — the first 
settled government, therefore, which is formed in that country, must prohibit 
the further exportation of a substance so important to the national interests. It 
is a matter not unworthy of the attention of chemists, therefore, to consider 
whether a mixture similar to the guano, and of equal efficacy, cannot be form- 
ed by art — not only at a cost so reasonable as at once to make the British 
farmer independent of the importer, — but also in such abundance as at the same 
time to place so valuable a manure within the reach of all. 

The following mixture contains the several ingredients found in guano in 
nearly the average proportions ; and I believe it is likely to be at least as effica- 
cious as the natui-al guano, for all the crops to which the latter has hitherto been 
applied in this country: — 

3 15 lbs. [7 bushels] of bone dust at 2s. 9d. per bushel 
100 lbs. of sulphate of ammonia,+ containing 35 lbs. of ammo- 
nia at 20s. a cwt ....... 

5 lbs. of pearl-ash ........ 

100 lbs. of common salt 

11 lbs. of dry sulphate of soda 

bSl .\hs. of artijlcial guano cost ...... 2 1 

• The first contained also 8 per cent, and the second 1| per cent, of sand, which has been 
left out of the true composition of the guano considered as free from sand. 

t Sulphate of ammonia is now manufactured largely at Glasgow, and may be had for less 
than 20s. a cwt. 

c 



£. 


s. 


d. 





19 








18 








1 








2 








1 






26 



ON EXPERIMKxNTS WITH GUANO. 



[Appendix, 



The quantity here indicated may be intimately mixed with 100 lbs. of chalk, 
and will be fully equal in efficacy, I believe, to 4 cwt. of guano, now selling 
at je5. 

At the same time it is desirable that the I'elative efficacy both of this mixture 
(artificial guano), and of the American guano, should be tried by actual experi- 
ment in compai'ison with other substances of known value, and which are 
supposed to act in a way somewhat similar. The substances with which I 
would suggest that such comparative experiments should, in the first place, be 
made, are fjfrm-yard manure, bone dust, and rape dust, and the following 
scheme exhibits the proportions in which they may be added to the different 
plots of land on which the experiments are intended to be made : — 



20 tons of 
farm-yard manure. 


20 bushels of 

bones 
with ashes. 


6 cwt. of guano, 

mixed with 
chalk or gypsum. 


6 cwt. of 
artificial guano. 


10 tons do. 

with 10 bushels of 

bone dust. 


20 cwt. of 
rape with ashes. 


10 Ions of farm- 
yard manure with 
3 cwt. of guano. 


10 tons of farm-yard 
manure with 3 cwt. 
of artificial guano. 


10 tons do. 

wtth 10 cwt. of 

rape dust. 


10 cwt. of 

rape with 3 cwt. 

of guano. 


10 tons do. with 
2 cwt. of guano. 


10 tons do. with 2 

cwt. of artificial 

guano. 



The practical farmer need not be deterred by the formidable an*ay of experi- 
ments above suggested. He may try any two or three of them, and his results 
will be valuable in propoi'tion to the accuracy with which his land is measured 
and his manures and ci-ops weighed. I have taken 20 tons of farm-yard manure 
as a standard, though in many highly farmed parts of the country no more than 
15 tons are usually applied. Twenty bushels of bones are recommended by the 
Doncaster report, and I have lately found that in the Lothians 1 cwt. of rape 
dust is considered to replace 1 ton of farm-yard ^panure. This pi-oportion of 
course will vary with the quality of the latter manure ; but whatever quantity 
of this latter we take as the standard of comparison, it is easy to adjust the 
proportions of the other substances accordingly. I have not recommended any 
trial to be made with more than 6 cwt. of guano, because, where farm-yard 
manure is valued only at 6s. or 7s. per ton, 5 cwt. of the former would cost as 
much as 20 tons of the latter.*' 

The above experiments are intended to be made with the green crop, and to 
be continued during an entire rotation :t any pair of them, however, may be 
tried on single crops, whether of corn or of turnips and potatoes. In this way 
guano ought also to be tried against nitrate of soda and against bones, upon 
seeds and upon old grass-lands. The mode in which such experiments may 
be made will speedily suggest themselves to the intelligent farmer. In all 
cases the results should be accurately recorded, and, if possible, published. 

* When this paragraph was written, the price of guano was 25s. a cwt. ; it is now (May, 
1842) reduced to 15s. » v j, 

t By this I mean that the effect of these several manures, applied once for all to the green 
crop at the commencement of the rotation, should be traced on each successive crop (hroueb 
the entire course of cropping. 



No. F.J OP THE PHYSICAL PROPERTIES OP THE SOIL. ' 27 

No. V. 

OF THE EXAMINATION AND ANALYSIS OF SOILS. 

l*^. Szlectiort of spezimens of soils. — In the same field different varieties of soil 
often occur, and some recommend that in collecting a specimen for analysis, 
portions should be taken from different parts of the field and mixed together, 
by which an average quality of soil would be obtained. But this is bad advice, 
when the soils in different parts of the field are really unlike. Suppose one 
part of a field to be clay, and another sandy, as is often the case in this county, 
and that an average mixture of them is submitted to analysis, the result you 
get will apply neither to the one part of the field nor to the other — that is, it 
will be of little or no value. In selecting a specimen of soil, therefore, one or 
two pounds should be taken from each of four or five parts of the field where 
the soil appears nearly alike, these should be well-mixed together and dried in 
the open air or before the fire. Two separate pounds should then be taken 
from the whole for the purpose of analysis, or if it is to be sent to a distance 
should be tied up in clean strong paper, or what is much better, should be en- 
closed in clean well-corked bottles. 

I. — OP THE PHYSICAL PROPERTIES OF THE SOIL. 

2-. D3t€rniinaUon of the density of the soil. — In order to determine the den- 
sity of the soil, a portion of it must be dried at the temperature of boiling 
water (21 2° ), till it ceases to lose weight, or upon a piece of white paper in an 
oven at a heat not great enough to render the paper brown. A cominon phial 
or other small bottle peifectly clean and dry' may then be taken and filled up 
to a mark made with a file on the neck, with distilled or pure rain water, and 
then carefully weighed. Part of the water may then be poured out of the 
bottle, and lOOD grains of the dry soil introduced in its stead, the bottle must 
then be well shaken to allow the air to escape from the pores of the soil, filled 
up again with water to the m irk on the neck, and again weighed. The weight 
of the soil, divided by the difference between the weight of the bottle with soil 
ani water and th3 sum of the weights of the soil and the bottle of water to- 
gether, gives the specific gravity. 

Thus, let the bottle with water weigh 2000 grains, and with water and soil 
2800, then- 
Grains. 

The weight of the bottle with water alone = 2000 

The weight of the dry soil 1000 

Sum, being the weight which the bottle with the soil and water ) 

wonl I have had co\x\di i\\t soil have been introduced without > 3000 
displacing any of the water ) 

But the weight of the bottle with soil and water was .... 2600 

Difference, being the weight of water taken out to admit lOOO ) .r.r. 
grains of dry soil \ 

Therefore^ 1000 grains of soil have the same tndk as 400 grains of water, or 
the soil is 2| times heavier than water, since 1000-^400 =2o its specific 
gravity. 

3°. D -termination of the absolute weight. — The absolute weight of a cubic 
foot of solid rock is obtained in pounds by multiplying its specific gravity by 
63| — the weight in pounds of a cubic foot of water. But soils arc porous, and 
contain more or less air in their interstices according as their particles are more' 
or less fine, or as they contain more or less sand or vegetable matter. Fine 
sands ai-e heaviest, clays next in order, and peaty soils the lightest. The 
simplest mode of determining their absolute weight, therefore, is to weigh an 
exact imperial half pint of the soil in any state of dryness, when this weight 



28 OP THE PHYSICAL PROPERTIES OP THE SOIL. [Appendix, 

multiplied by 150, will give very nearly the weight of a cubic foot of the soil in 
that state. 

4c°. Detcrminatian of the relative proportions of gravel, sand, and day. — Five 
hundred grains of the dry soil may be boiled in a flask half full of water till the 
particles are thoroughly separated from each other. Being allowed to stand 
for a couple of minutes, the water with the fine matter floating in it may be 
poured off into another vessel. This may be repeated several times till it ap- 
pears that nothing but sand or gravel remains. This sand and gravel is then 
to be washed completely out of the flask, dried, and weighed. Suppose the 
weight to be 300 grains, then 60 per cent.* of the soil is sand and gravel. The 
sand and gravel are now to be sifted through a gauze sieve more or less fine, 
when the gravel and coarse sand are separated, and may be weighed and their 
proportions estimated. 

These separate portions of gravel and sand should now be moistened with 
water and examined carefully with the aid of a microscope, with the view of 
ascertaining if they are wholly silicious, or if they contain also fragments of • 
different kinds of rock — sand-stones, slates, granites, traps, lime-stones, or iron- 
stones. A few drops of strong muriatic acid (spirit of salt) should also be 
added — when the presence of lime-stone is shown more distinctly by an effer- 
vescence, which can be readily perceived by the aid of the glass, — of per-oxide 
of iron by the brown colour which the acid speedily assumes, — and of black 
oxide of manganese by a distinct smell of chlorine which is easily recognised. 
In the subsequent description of the soil, these points should be carefully noted. 

Suppose the sand and gravel to contain half its weight of fine sand, then 
our soil would consist of coarse sand and small stones 30 per cent., fine sand 
30 per cent., clay and other lighter matters 40 per cent. 

5°. Absorbing power of the soil. — A thousand grains of the perfecdy dry soil, 
crushed to powder, should be spread over a sheet of paper and exposed to the 
air for twelve or twenty-four hours, and then weighed. The increase of weight 
shows its 'power of absorbing moisture from the air. If it amount to 15 or 20 
grains, it is so far an indication of great agricultural capabilities. 

6°. Its power of holding viatcr. — This same portion of soil may now be put 
into a funnel upon a doxMei filter and cold water poured upon it, drop by drop, 
till the whole is wet and the water begins to trickle down the neck of the filter. 
It may now be covered with a piece of glass and allowed to stand for a few 
hours, occasionally adding a few drops of water, until there remains no doubt 
of the whole soil being perfectly soaked. The two filters and the soil are then 
to be removed from the funnel, the filters opened and spread for a few minutes 
upon a linen cloth to remove the drops of water which adliere to the paper. 
The wet soil and inner filter being now put into one scale, and the outer filter 
in the other, and the whole carefully balanced, the true weight of the wet soil 
is obtained. Suppose the original thousand grains now to weigh 1400, then 
the soil is capable of holding 40 per cent, of water.t 

7°. Rapidity withvMch the soil dries. — The wet soil with "its filter may now 
be spread out upon a plate and exposed to the air, in what may be considered 
ordinary circumstances of temperature and moisture, for 4, 12, or 24 hours, and 
the loss of weight then ascertained. This will indicate the comparative ra- 
pidity with which such a soil would dry, and the consequent urgent demand 
for draining, or the contrary. As gi'cat a proportion of the Avater is said to 
evaporate from a given weight of sand saturated with water, in 4 hours, as 
from an equal weight of pure clay in 11, and of peat in 17 hours — when placed 
in the same circumstances. 

8°. Power of absorbing heat from the sun. — In the preceding experiment a por- 
tion of pure quartz sand or of pipe clay may be employed for the purpose of 

• As 500 : 300 : : 100 to 60 per cent, 
t That is, one filter within another. 
X 1000 : 400, the increase of weight as 100 : 40. 



No. K] OF THE PHYSICAL PROPERTIES OP THE SOIL. 29 

obtaining a comparative result as to the rapidity of drying. The same method 
may be adopted in regard to the power of the soil to become warm under the 
influence of the sun's rays. Two small wooden boxes, containing each a 
layer of one of the kinds of soil, two inches in depth, may be exposed to the 
same sunshine for the same length of time, and the heat they severally acquire 
determined by a thermometer, buried about a quarter of an inch beneath the 
surface. Soils are not found to differ so much in the actual temperature they 
are capable of attaining under such circumstances — most soils becoming 20° 
or 30° warmer than the surrounding air in the time of summer — as in the re- 
lative degree of rapidity with which they acquire this maximum temperature — 
and this, as stated in the text, appears to depend chiefly upon the darkness of 
their colour. The determination of this quality, therefore, except as a matte* 
of curiosity, may, at the option of the experimenter, be dispensed witli. 

II. OF THE ORGANIC MATTER PRESENT IN THE SOIL. 

9°. Determination of the pcr-ccntage of organic matter. — The soil must be 
thoroughly dried in an oven or othei-wise, at a temperature not higher than be- 
tween 250° to 300° F. Humic and vflmic acids will bear this latter tempera- 
ture without change. An accurately weighed portion (100 to 200 grains) must 
then be burned in the open air, till all the blackness disappears. This is best 
done in a small platinum capsule over an argand spirit or gas lamp. The loss 
indicates the total weight of organic matter present. It is scarcely ever pos- 
sible, however, to render soils absolutely dry without raising them to a tem- 
perature so high as to char the organic matter present, and hence its weight, as 
above determined, will always somewhat exceed the truth, the remaining water 
being driven oiF along witli the organic matter when the soil is heated to red- 
ness. This excess, also, will in general be greater in proportion to the quantity 
of clay in the soil, since this is the ingredient of most soils from which the 
water is expelled with the greatest difficulty. 

10°. Determinatio7i of the humic acid. — This acid, whether merely mixed with 
the soil, or combined with some of the lime and alumina it contains, is extracted by 
boiling with a solution of the common soda of the shops. Into about two ounces 
by measure of a saturated solution of this salt, contained in a flask, 200 or 300 
grains of soil, previously reduced to coarse powder, are introduced, an equal 
bulk of water added, and the whole boiled or digested on the sand bath with 
occasional shaking for an hour. The flask is then removed from the fire, filled up 
with water, well shaken, and the particles of soil afterwards allowed to subside. 
The clear liquid is then poured off". If it has a brown colour it has taken up 
some humic acid. In this case, the process must be repeated once or twice 
with fresh portions of the soda solution, till the whole of the soluble organic 
matter appears by the pale colour of the solution to be taken up. These coloured 
solutions are then to be mixed and filtered. The filtering generally occupies 
considerable time, the humic and ulmic acids clogging up the pores of the filter 
in a remarkable manner, and permitting the liquid to pass through sometimes 
with extreme slowness. 

When filtered, muriatic acid is to be slowly added to the coloured liquid — 
which should be kept in motion by a glass rod — till effervescence ceases, and 
the whole has become dictinctly sour. On being set aside the humic acid falls 
in brown flocks. A filter is now to be dried and carefully weighed,* the liquid 
filtered through it, and the humic acid thus collected. It must be washed in the 
filter with pure water — rendered slightly sour by muriatic acidt — till all the soda is 

* This is best effected by putting the filter into a covered oorcelain crucible of known 
weight, and heating it for ten minutes over a lamp or otherwise, at a temperature which 
just does not discolour the paper, allowing then the crucible to cool under cover, and when 
cold weighing it. The increase above the known weight of the crucible is that of the filter, 
which, besides being recorded in the experiment book, should also be marked in several 
places on the edge of the filter with a black lead pencil. 

t This is to prevent in some measure the humic acid from passing through the filter, 
which it is very apt to do, when the saline matter is nearly washed out of it. 



30 OP THE ORGANIC MATTER PRESEXT IN THE SOIL. [Appendix, 

separated from it,* when it is to be dried at 250° F., till it ceases to lose weight. 
The final weight, minus that of the filter, gives the quantity of humic acid con- 
tained in the portion of soil submitted to examination. As it is rarely possible to 
wash the humic acid perfectly upon the filter, rigorous accuracy requires that the 
filter and acid should be burned after being weighed, and the weight of ash left, 
minus the known weight of ash left by the filter,t deducted from that of the 
acid as previously determined. It is to be observed here that by this, which 
is really the only available method we possess of estimating the humic acid, a 
certain amount of loss arises from its not being wholly insoluble, the acid 
liquid which passes through the filter being always more or less of a brown 
colour.+ 

11°. Determination of the insoluble humus. — Many soils after this treatment 
with carbonate of soda are still more or less of a brown colour, evidently due 
to the presence of other organic matter. To separate this, Sprengel recom- 
mends to boil the soil, which has been treated with carbonate of soda, and 
which we suppose still to remain in the flask, with a solution of caustic potash, 
repeated, if necessary, as in the case of the soda solution. By this boiling, 
.the vegetable matter, which was insoluble in the carbonate of soda, is changed 
in constitution and dissolves in the caustic potash, giving a brown solution, 
from which it may be separated in brown flocks by the addition of muriatic 
acid, and then collected and weighed as above described. 

In some soils, also, distinct portions of vegetable fibre, such as portions of 
roots, &c., are present, and may be separated, mechanically dried, and weighed. 

12°. Of other organic substances present in the soil. — The sum of the weights 
of the above substances deducted from the whole weight of organicmatter, as 
determined by burning, gives that of other organic substances present in the 
soil. The quantity of these is in general comparatively small, and, unless they 
are soluble in water, there is no easy method of separating them, and determin- 
ing their weight. The following two methods, however, may be resorted to : — 

.1°. Half a pound or more of the moist soil may be boiled with two separate 
pints of distilled water, the liquid filtered and evaporated to a small bulk. From 
clay soils, when thus boiled with water, the fine particles do not readily subside. 
Sometimes, after standing for several days, the water is still muddy, and passes 
muddy through the filter, but, after being evaporated, as above recommended, to 
a small bulk, most of the fine clayey matter remains on the paper when it is 
again filtered. As soon as it has thus passed through clear, the liquid may be 
evaporated to perfect dryness at 2.30° F., and weighed. Being now treated 
with water — a portion will be dissolved — this must be poured off", and the inso- 
luble remainder again perfectly dried and weighed. If this remainder be now 
heated to redness in the air, any organic matter it contains will be burned off, 
and its weight ascertained by the loss on again weighing. Th^s loss may be 
considered as humic acid rendered insoluble by drying.§ It does not require to 
be added to the weight of humic acid already determined (10°), because in 
that experiment a portion of soil was employed which had not been boiled in 
water, and from which therefore the carbonate of soda would at once extract 
all the humic acid. The present experiment need only be made when it is de- 

* This is ascertained by collecting a few drops of what is passing through upon a piece of 
clean glass or platinum, and drying them over the lamp, when, il a perceptible slain or spot is 
left, the substance is not sufficiently washed. 

t The ash left by the paper employed for filters should always be known. This is ascer- 
tained, once for all, by drying a quantity of it in the way described in the previous note, 
weighing it in this dry state, burning it, and again weighing the ash that is left. In good 
filtering paper, the ash ouglit not to exceed one per cent. 

X The portion which thus remains in the solution may be precipitated by adding a small 

S|uantity of a solution of alum, and afterwards pouring in ammonia in excess. The alumina 
alls coloured by the organic matter, and after being collected on a filter, washed, and dried, 
the weight of organic matter in the precipitate may be determined approximately as des- 
cribed under 12° (2°). 

§ See Lecture xiii., § I. 



No. v.] OF THE ORGANIC MATTER PRESENT IN THE SOIL. 31 

slrable to ascertain how much humic acid a soil contains in a state in which it 
is soluble in water. Where ammonia, potash, or soda is present in the soil, 
some chemists consider this quantity to be very considerable, and to exercise 
an important influence upon vegetation. 

That which was taken up by water from the dried residuum is again to be 
evaporated to dryness, dried at 150°, weighed, and burned at a low red heat. 
The loss is organic matter, and may have been crenic or apocrenic, or some 
other of the organic acids formed in soils, the compounds of which, with lime, 
alumina, and prot-oxide of iron, are soluble in water. If any little sparkling or 
burning like match-paper be observed during this heating to redness, it may be 
considered as an indication of the presence of nitric acid— in the form of ni- 
trate of potash, soda, or lime. In this case the loss by burning will slightly ex- 
ceed the true amount of organic matter present, owing to the decomposition and 
escape of the nitric acid also. The mode of estimating the quantity of this acid, 
when it is present in any sensible proportion, will be hereafter described. 

2'^. The caustic potash employed to dissolve the insoluble humus (11") takes 
up also any alumina wliich may have been in combination with the humic 
acid or may still remain united to the mudesous* or other organic acids. When 
the solution is filtered and the humic acid separated by the addition of muriatic 
acid till the liquid has a distinctly sour taste, this alumina, and the acids with • 
which it is in combination, still remain in solution. After the brown flocks of 
humic acid, however, are collected on the filter, the alumina may be thrown down 
from the filtered solution by adding caustic ammonia to the sour liquid, until 
it has a distinctly ammoniacal smell. The light precipitate which falls must 
be collected on a filter and washed with hot water till the potash is as completely 
separated as possible. It is then to be dried at 300'^ F., weighed and heated 
for some time in a close crucible over the lamp, at a temperature which begins 
to discolour it, and again weighed. Being now burned in the air till it is quite 
v/hite, and weighed, the last loss may be considered as mudesous or some simi- 
lar acid. 

The reason why this second method of diying over the lamp is here re- 
commended, is, that alumina and nearly all its compounds part with their 
water with great difliculty, and even with the precautions above indicated, it is 
not unlikely that a larger per-centage of organic matter may thus be indicated, 
than in reality exists in the soil. The check which the accurate experimenter has 
upon all these determinations is this, that the sum of the several weights of the 
hvmiic acid, the insoluble humus, the vegetable fibre, and of the crenic and mu- 
desous acids, if present, should be somewhat less than that of the whole com- 
bustible organic matter, as determined by burning the dry soil in the open air 
(9"). This quantity we have seen to be in most cases greater than the truth, 
because any remaining water or any nitric acid the soil may contain, are at the 
same time driven off. 

I may further remark upon this subject that the quantity of alumina thus 
dissolved by the caustic potash is in most soils very small, and the quantity of 
organic matter by which it is accompanied in many cases so minute, that the 
determination of it may be considered as a matter of curiosity, rather than oiie 
of practical importance. 

III. — OF THE SOLUBLE SALINE MATTER IN THE SOIL. 

13°. With a view to determine the nahire of the soluble saline matter in the 
soil, a preliminary experiment must be made. An unweighed portion must be 
introduced into five or six ounces of boiling distilled water in a flask, and kept 
at a boiling temperature, with occasional shaking for a quarter of an hour. It 
may then be allowed to subside, after which the liquid is to be filtered till it 
passes through clear. It is then to be tested in the following manner. Small 

■ Except where gypsum is present in the insoluble portion, which is not unfrequently the 
case, when the loss will be partly water— since gypsum, after being dried at 250°, loses still 
about 208 per cent, of water when heated to redness. 



32 OF THE SOLUBLE SALINE MATTER IN THE SOIL. [Appendix, 

separate portions are to be put into so many clean wine glasses, and the effect 
produced upon these by different chemical substances carefully noted. 
if with a few drops of — 

a. Nitrate of Baryta, it gives a white powdery precipitate, which does not 
disappear on the addition of nitric or muriatic acid, the solution contai7is sulphu- 
ric acid. If the precipitate does appear, it contains carbonic acid. In this lat- 
ter case, the liquid will also effervesce on the addition of either of the acids 
above mentioned. 

b. If with oxalate of ammonia, it gives, either immediately or after a time, a 
white cloud, it contains lime,* and the greater the milkiness, the larger the 
quantity of lime may be presumed to be. 

c. If with nitrate of silver, it gives a white curdy precipitate, insoluble in pure 
nitric acid, and speedily becoming purple in the sun, it may be presumed to 
contain chlorine. 

d. If with caustic ammonia, it gives a pure white gelatinous precipitate, it 
contains either alumina, or magnesia, or both. In this case, muriatic acid must 
be added till the precipitate disappears, and the solution is distinctly acid. If 
on the addition of ammonia in excess, the precipitate reappears undiminished 
in quantity, it contains alumina only. If it be distinctly hss in quantity, we 
may infer the presence of both magnesia and alumina ; and if no precipitate now 
appears, that it contains magnesia only. If a large quantity of magnesia be present, 
it may be necessaiy to re-dissolve and acidify the solution a second time be- 
fore, on the ?c-addition of ammonia, the precipitate would entirely disappear. 

If the precipitate, by ammonia, have more cr less of a brown colour, the pre- 
sence of iron, and perhaps inangauese, may be inferred. If, on the second 
addition of ammonia, the colour of the precipitate has disappeared, it has been 
due to the manganese only— if it still continue brow^n, it is owing chiefly or 
altogether to the presence of oxide of iron. If the colour of the precipitate, by 
ammonia, be very dark, it consists almost entirely of oxide of iron, and may 
contain little or no alumina, — when it is only more or less brown, the presence 
of both alumina and oxide of iron may with certainty be inferred. 

e. If, after the first addition of ammonia, the solution be filtered to separate 
the alumina, the oxides of iron and manganese, and the magnesia that may be 
thrown down — if oxalate of ammonia be then added till all the lime falls, and 
the liquid be again filtered, evaporated to dryness, and then heated to incipient 
redness in the air, till the excess of oxalate of ammonia is destroyed and driven 
off — and if a soluble residue then remain,! it is probable that potash or soda, or 
both, are present. If, on dissolving this residue in a little water, the addition of 
a few drops of a solution of tartaric acid to it produce a deposite of small 
colourless crystals (of cream of tartar), or if a drop of a solution of bi-chlo- 
ride of platinum produce in a short time a yellow powdery precipitate, it con- 
tains poto.sh. If no precipitate is produced by either of these — re-agents as they 
are called — the presence of soda may be inferred. If the yellow precipitate, 
containing potash and platinum, be separated by the filter, and the solution, after 
being treated with sulphuretted hydrogen and filtered to separate the excess of 
bi-chloride of platinum, be evaporated to dryness — if, then, a soluble saline 
residue still remain, the solution contains soda as well as potash. 

It is to be observed that some magnesia, if present, may accompany the pot- 
ash and soda through these several processes. After the separation of the potash, 
a little caustic ammonia will detect the presence of magnesia, but it will rarely 
be found so far to interfere with this preliminary examination as to prevent the 
experimenter from arriving at correct results (see p. 35, /). 

* The learned reader will understand why, for the sake of simplicity, I take no notice of 
substances not likely to be present in the soil — as, for example, baryta, which would here be 
thrown down along with the lime, or of oxalic acid, which, equally with the sulphuric or car- 
bonic (a), would give a white precipitate with nitrate of baryta. 

t Not precipitated from its solution by ammonia, for if precipitated it is partly at least 
chloride of magnesium. 



No. v.] OP THE SOLUBLE SALINE MATTER IN THE SOIL. 33 

/. If the addition of bi-chloride of platinum to the solution directly filtered 
from the soil give a yellow precipitate, it contains either potash or ammonia. 
If, when collected on the filter, dried, and heated to bright redness in the air, 
white fumes are given off by this yellow precipitate, and only a spongy mass 
of metallic platinum remains behind, the solution contains armiwnia only. If, 
with the platinum, be mixed a portion of a soluble substance having a taste 
like that of common salt, and giving again a yellow precipitate with bi-chloride 
of platinum, it contains potash — and if the spongy platinum contained in the 
burned mass, after prolonged heating, amount to more than 57 per cent, of 
its weight, or if it be to the soluble matter in a higher proportion than that of 
4 to 3, the solution contains both folash and ammonia. 

The presence oi amvwnla in the saline substance, or in the concentrated solu- 
tion, is more readily detected by adding a few drops of a solution of caustic 
potash, when the smell of ammonia becomes perceptible, or if in too small 
quantity to be detected by the smell, it will, if present, restore the blue colour 
to reddened litmus paper. This experiment is best made in a small tube, 

g. If, when the solution, obtained directly from the soil, is evaporated to dry- 
ness, and the residue heated to redness in the air, a deflagration or burning like 
match-paper be observed, nitric acid is present. Or, if the dry mass, when put 
into a test tube with a little muriatic acid, evolves distinct red fumes on bemg 
heated, or enables the muriatic acid to dissolve gold-dust, and form a yellow 
solution ; or, if to a colourless solution of green vitriol (sulphate of iron), 
introduced into the tube along with the muriatic acid, it imparts more or less of a 
brown colour — in any of these cases the presence of nitric acid may with cer- 
tainty be inferred. It will be only on rare occasions, however, that salts, so 
soluble as the nitrates, will be found in sensible quantity in the small portion 
of a soil likely to be employed in these preliminary experiments. 

//. If ammonia throw down nothing (see under ^) from the solution, and if 
no precipitate appear when chloride of calcium or magnesium is afterwards 
added, the solution towicCms no phosplwric acid. But if ammonia cause a pre- 
cipitate, and after this is separated by the filter, nothing further falls on adding 
either of the above chlorides, the phosphoric acid, if any is present, will be con- 
tained in the precipitate which is upon the filter. Let this, after being well 
washed with distilled water, be dissolved oiF with a little pure nitric acid 
diluted with water, and then neutralized as exactly as possible with ammonia. 
If a solution of acetate (sugar) of lead now throw down a white precipitate, phos- 
Dhoric acid is present. The phosphate of lead — the white precipitate which 
alls — melts readily before the blow-pipe, and, on cooling, crystallizes into a bead 
with beautiful ciystalline facets. 

Or — if the precipitate thrown down by ammonia be wholly or in part insolu- 
ble in pure acetic acid (vinegar), that which is undissolved contains phosphoric 
acid. If acetic acid dissolve the whole, it may be inferred that no phosphoric 
acid is present in the soil. 

But if no precipitate be thrown down by ammonia, instead of the chloride of 
calcium above recommended, a few drops of a dilute solution of alum may be 
mixed with the solution, after adding the ammonia, and the whole well shaken. 
If the white precipitate, which now falls, dissolve wholly in acetic acid, no phos- 
phoric acid is present, and vice versa. 

These preliminary trials being made, notes should be kept of all the appear- 
ances presented, as the method to be adopted for separating and determining 
the weight of each substance will depend upon the number and nature of those 
which are actually found to be present, . , , ^>^^^,_ 

14°. Determination of the quantities of the several constifuetits of the soluble 
salitie matter. — The quantity of soluble saline matter extracted from a mode- 
rate qtiantity of any of our soils is rarely so great as to admit of a rigorous 
analysis, and the preceding determination of the kind of substances it contains 
will be in most cases sufficient. Gases may occur, however, in which much 
C» 



I 



34 



OK THE SOLUBLE SALINE MATTER IN THE SOIL. 



[Appendix, 



saline matter may be obtained ;* it will be proper, thei-efore, briefly to state 
the methods by which the respective quantities of each constituent may be ac- 
curately determined. 

a. Estimation of the Sidphnric Acid. — The solution being gently warmed, a 
few drops of nitric acid are to be added until the solution is slightly acid, and 
any carbonic acid that may be present is expelled, after which nitrate of baryta 
is to be added to the solution as long as any thing falls. The white precipi- 
tate (sulphate of baryta) is then to be collected on a weighed filter, well washed 
with distilled water, dried over boiling water as long as it loses weight, and 
then weighed. The weight of the filter being deducted,t every 100 grains of 
the dry powder are equal to 34-37 grains of sulphuric acid. 

b. Estimation of the Chlorine. — The solution of nitrate of silver must be add- 
ed as long as any precipitate falls, the precipitate then washed, dried at 212° F., 
and weigTied as before. Every 100 grs. of chloride of silver indicate 24-67 grs. 
of chlorine, or 40-88 gi's. of common salt. 

c. Estimation of the Lime. — A little diluted muriatic acid being added to throw 
down the excess of silver, and a little sulphuric acid to separate the excess of 
baryta, added in the former operations, and the precipitates separated by fil- 
tration — caustic ammonia is to be poured in, till the solution is distinctly alcaline. 

' This is the case with the rich soils of India and Egypt, and of other warm climates. 
This will appear from the following analyses of some Indian soils, made on the spot by Mr. 
Fleming, of Barochan, during the hours of leisure left him by his more important duties : — 

Analysis af soils in North and- South Behar, Bengal Presidency — (200 grains oj 

each being analysed.) 



22 



20 



20 



19 



l-S 



12 



14 



ol o 



o:o 



10 



7 12 



8 13 



4 20 



14 



20 



16 



12 



2^ 






126 



115 



110 



130 



140 



152 



■©■a rt 



14 



REMARKS. 



1°. Near Gya, South Behar— Of a dark colour, soapy 
to the touch when moist, hard and cracks when dry ; 
yields a crop of rice and one of wheat every year. Ne- 
ver lies fallow, but is covered with water during part of 
the rainy season, and is productive — from 30 to 50 
bushels of wheat per acre. 

2°. Soil from the same district. — Also soapy when 
moist and cracks when dry — rather more productive 
than No. 1. 

3°. From the same district.— Heavy red clay soil, 
producing wheat, pease, cotton, or poppy in the dry 
season, and Indian corn and millet in the wet season ; 
not inundated in the rains, and sometimes manured 
with ashes of wood and cow dung. 

4°. Soil from North Behar, Tirboot. — A deep loam, 
yielding two crops yearly ; not inundated, producing 
wheat, barley, Indian corn, indigo, poppy, &.c. From 
25 to 35 bushels of wheat per acre ; is not usually 
manured. 

5°. Tirhoot. — Soillight coloured ; producing nearly 
the same crops, but not so productive as No. 4. Saline 
etflorescence in patches. 

6°. Tirhoot.— Not so productive as No. 5, and some 
patches nearly sterile from the saline efflorescence, 
except in the rainy season, when it produces good 
crops of Indian corn. Soil light coloured. 



I have already alluded (Lecture VIII., p. 159) to the influence which this large proportion 
of saline matter exercises upon the luxuriance of the vegetation. 

+ Or the whole may be heated to redness in the air, and the filter burned away. In this 
case the weight of ash left by the paper must be ascertained by previous trials, and the due 
proportion deducted from the weight of the sulphate. 



No. v.] OF THE SOLUBLE SALINE MATTER IN THE SOIL. 35 

If no precipitate fall, oxalate of ammonia is to be added as long as any white 
powder appears to be produced. The solution must then be left to stand ovejf 
night — that the whole of the lime may separate, — the white powder afterwards 
collected on a filter, Washed, dried, and burned with the filter, at a low red heat. 
The grey powder obtained is carbonate of lime, every 100 grs. of which con- 
tain 43*71 grs. of lime. 

d. Estimalion of the Oxide of Iron and of the Alumina. — But if a precipitate 
fall on the addition of ammonia, as above prescribed— the solution may con- 
tain magnesia, alumina, and the oxides of iron, and manganese. In this case 
the precipitate is to be re-dissolved by the addition of muriatic acid till it is dis- 
tinctly acid, and ammonia again added in slight excess. If any precipitate now 
fall, it will consist only of alumina and oxide of iron, unless magnesia and 
oxide of manganese be present in large proportion, when a minute quantity of 
each may fall at the same time. 

The precipitate is to be collected on the filter as quickly as possible, — the fun- 
nel being at the same time covered with a plate of glass to prevent as much as 
possible the access of the air, — washed with distilled water, and then re-dissolved 
in muriatic acid. This is best effected by spreading out the filter in a small 
porcelain dish, adding dilute acid till all is dissolved, and then washing the pa- 
per Well with distilled water. A few drops of nitric acid are then to be added, 
and the solution heated, to peroxidize the iron. A solution of caustic potash 
added in excess will at first throw down both the oxide of iron and alumina, but 
will afterwards re-dissolve the alumina, and leave only the oxide of iron. This 
is to be collected on a filter, washed, dried, heated to redness, and weighed. 
Every 100 grains of this peroxide of iron are equal to 89-78 grains of protoxide, 
in which state it had most probably existed in the original solution. 

To the potash solution muriatic acid is added till the alkali is saturated, or till 
the solution reddens Utvius paper * when the addition of ammonia precipitates 
the alumina. As it is difficult to wash this precipitate perfectly free from potash, it 
is better to dissolve it again in muriatic acid, and to re-precipitate it by caustic 
ammonia. When well washed, dried, and weighed, this precipitate gives the true 
quantity of alumina present in the portion of salt submitted to analysis. 

e. Estimation of the Manganese. — To the ammoniacal solutions from which 
the oxalate of lime has been precipitated (t), a solution of hydro-sulphuret of 
ammonia is to be added. The manganese will fall in the form of a flesh red 
sulphuret. When this precipitate has fully subsided, it must be collected on the 
filter and washed with water containing a very little hydro-sulphuret of ammo- 
nia. The filter is then put into a glass or porcelain basin, the precipitate dis- 
solved off by dilute muriatic acid, and the solution filtered, if necessary. A so- 
lution of carbonate of potash then throws down carbonate of manganese, which 
is collected, dried, and heated to redness in the air. Of the brown powder ob- 
tained 100 grains indicate the presence of 93*84 grains of protoxide of manganese 
in the salt or solution under examination. 

f. Estimation of the Magnesia. — If no potash or soda be pi*esent in the residual 
solution, the determination of the magnesia is easy. A few drops of muriatic 
acid are added, and the whole gently heated, and afterwards filtered, to separate 
the sulphur of the excess of hydro-sulphuret of ammonia previously added. The 
solution is then evaporated to dryness, and the dry mass heated to redness to 
drive off all the ammoniacal salts previously added. A few drops of diluted sul- 
phuric acid are added to what remains, to change the whole of the magnesia 
into sulphate, the mass again heated to redness and weighed. One hundred 
grains of this sulphate indicate the presence of 34*01 grs. of pure magnesia. 

But if potash or soda be present — the weight of which it is desirable to deter- 
mine — the simplest method is to take a fresh portion, 15 to 20 grains, of the 

• Litmus paper is paper stained by dipping it into a solution of litmus, a vegetable blue co 
lour, prepared and sold for the purpose of detecting the presence of free acids, by which it 
is reddened. 



36 OP THE SOLUBLE SALINE MATTER IN THE SOIL. [Appelldix, 

saline matter under examination. If any sulphuric acid be present in it add ni- 
trate of baryta drop by drop to the solution till the whole of the acid is exactly 
thrown down — if possible, no excess of baryta being left in the solution — then 
precipitate the alumina and oxides of iron and manganese, and the lime, if any 
of these bs present, and, finally evaporate to dryness, and heat to redness as be- 
fore. The dry mass is now to be dissolved in water, adding, if necessary to 
complete the solution, a few drops of muriatic acid. A quantity of red oxide of 
mercury is then to be added to the concentrated solution, and the whole boiled 
down to dryness. Water now dissolves out the potash and soda only, and 
leaves the magnesia mixed with oxide of mercury. This is to be collected on 
a filter, washed — not with too much water — and heated to redness, when the 
magnesia remains pure, and may be weighed. 

g. Es'imatlou uf the Polish ani Soda. — The solution containing the potash 
and soda, is to be evaporated to dryness, and heated to redness to drive off any 
mercury it may contain. The weight of the mass which consists of a mixture 
of chloride of potassium with chloride of sodium (common salt) is accurately 
determined, it is then dissolved in a small quantity of water, and a solution of 
bi-chloride of platinum added to it in sufficient quantity. Being evaporated by 
a very g ntle heat nearly to dryness, weak alcohol is added, which dissolves the 
chloride of sodium and any excess of salt of platinum which may be present. 
The yellow powder is collected on a weighed filter, washed well with spirits, 
dried by a gentle heat and weighed on the filter. Every 100 grains indicate 
the presence of 1933 grains of potash, or 3056 grains of chloride of potassium. 
The quantity of chloride of sodium is estimated from the loss. The weight 
of the chloride of potassium above found, is deducted from that of the mixed 
chlorides previously ascertained, the remainder is the weight of the chloride of 
sodium. Every 100 grains of chloride of sodium (common salt) are equiva- 
lent to 5329 of soda. 

h. Estimation of the Ammonia. — If ammonia be present in the solution along 
with potash and other substances, the method by which it can be most easily 
estimated is to introduce the solution into a large tubulated retort, to add water 
until the solution amounts to nearly an English pint — then to introduce a quan- 
tity of caustic potash or caustic baiyta, and to distil by a gentle heat into a 
close receiver, containing a little dilute muriatic acid, until fully one half has 
passed over. Bi-chloride of platinum is then to be added to the solution, 
which has come over, previously x'endered slightly acid by muriatic acid, and 
the whole is evaporated nearly to dryness by a very gentle heat. Dilute alco- 
hol is then added to wash out the excess of the salt of platinum, and the yellow 
powder is collected on a filter, washed with spirit, dried by a very gentle heat, 
and weighed. One hundred grains indicate the presence of 7*69 grains of 
ammonia. 

Or the yellow powder, without being so carefully dried, may be heated to red- 
ness, when only metallic platinum will remain. One hundred grains of this 
metallic platinum indicate the presence of 17 39 grains of ammonia. 

i. Estimation of the Phosphoric Acid. — If phosphoric acid be present in the 
solution, it will be contained in the precipitate thrown down by ammonia (d). 
As it will never be found but in very small quantity, the rigorous determination 
of its amount is a matter of considerable difficulty. The following method 
already described (13°, h,) may be adopted. The precipitated alumina, oxide 
of iron, &c., thrown down by ammonia, after being di'ied, are to be mixed with 
three times their weight of pui'e dry carbonate of soda, and fused together in a 
platinum crucible. The fused mass is then to be treated with cold distilled 
water till eveiy thing soluble is taken up. The filtered solution is next to be 
gently heated and exactly neutralized with nitric acid, when a solution of ni- 
trate of silver will throw down a vMte precipitate of phosphate of silver, which 
is to be collected, dried, and weighed. Every hundred grains of it are equal to 
23-51 of phosphoric acid, or 4^-50 of bone earth. 



No. X''.] OF THE SOLUBLE SALINE MATTER IN THE SOlLi 37 

Or the filtered solution may be treated with inuriatic acid, ammonia added in 
excess, and then a solution of chloride of calcium. Bo7i,e earth will fall, which 
is to be collected, washed, heated to redness, and weighed. One hundred 
grains of it contain 4845 of phosphoric acid. The former method is probably 
the better, but neither of them will give more than an approximation to the truth. 

That portion of the fused mass which cold water has refused to take up is to 
be dissolved in muriatic acid, and again precipitated by ammonia. The clear 
solution which passes through is to be added to the first ammoniacal solu- 
tion (c), from which the lime is not yet thrown down, as when little alumina 
and oxide of iron are present, a small portion of lime and magnesia, if con- 
tained in the salt under examination, may have fallen along with them in com- 
bination with phosphoric acid. 

The alumina and oxide of iron which rest on the filter are to be separated 
and estimated as already described («). 

k. Estimation of the Carbonic Acid.—Tha lime and magnesia dissolved by 
cold diluted muriatic acid are partly in combination with carbonic acid and 
partly with the huaiic, ulmic, and other vegetable acids. 'l"o determine the 
carbonic acid, 100 grains of the soil dried at '2V2,'^, ore to be introduced into a 
small weighed flask, and then just covered by a weighed quantity of cold di- 
luted muriatic acid. After 13 hours, when the action has ceased, a small tube 
is to be introduced into the flask and air sucked through it till the whole of the 
carbonic acid is drawn out of the flask. The loss of weight will indicate the 
amount of carbonic acid very nearly. It would be more rigorously ascertained 
by fitting into the mouth of the flask a tube containing chloride of calcium, 
and then heating the solution to expel tlie carbonic acid. 

Every hundred grains of carbonic acid indicate the presence of 7724 grains 
of lime in the state of carbonate. The weight of lime in this state, deducted 
from the whole weight obtained as above (c), gives the quantity which is in 
combination with other organic acids. 

IV. OF THE INSOLUBLE EARTHY MATTER OF THE SOIL. 

15^^. When the soil has been washed with distilled water as above directed — 
it is to be treated in the cold with diluted muriatic acid — and allowed to stand 
with occasional stirring for 12 hours. By this means the carbonates of lime, 
magnesia, and iron, and the phosphates of lime, and alumina, are dissolved — 
with any lime, magnesia, oxide of iron, or alumina, which may have been in 
combination with organic acids. The iron, alumina, and phosphoric acid are 
to be precipitated by ammonia, the lime by oxalate of ammonia, and such other 
steps taken as may be necessary, according to the methods already described. 

16'^. The undissolved portion may now be treated with hot concentrated 
muriatic, kept warm and occasionally stiiTed for two or three hours, and the 
solution afterwards evaporated to dryness. The dry matter is then to be 
moistened with a few drops of muriatic acid, and subsequently treated with 
water. What remains undissolved is silica, which must be collected on a 
filter, dried, heated to redness, and weighed. 

The solution may contain oxide of iron, alumina, lime, magnesia, potash, 
and soda. Any of the four last substances, which may be detected in it, have 
most probably existed in the soil, in combination with silica — in the state of 
silicates. 

17°. But the soil may still contain alumina, not soluble in hot muriatic acid. 
To ascertain if this be the case, and to separate and determine this portion of 
the alumina, if present, either of two methods may be adopted. 

a. The residual soil may be drenched with concentrated sulphuric acid and 
heated for a considerable time till the sulphuric acid is nearly all driven off. 
On treating with water, and adding ammonia to the filtered solution, alumina, 
and oxide of iron, if any have been present, will be thrown down. If any 
alumina be thus separated, the treatment widi sulphuric acid must be repeat- 



38 



OF THE SOLUBLE SALINE MATTER IN THE SOIL. 



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No. v.] OF THE SOLUBLE iSALINB MATTER IN THE SOIL. 39 

ed. till on treating with water and ammonia, as before, no more alumina ap- 
pears. 

b. Or that portion of the soil on which hot muriatic acid refuses to act may 
be mixed with twice its weight of carbonate of soda, and heated in a platinum 
crucible till the whole is completely fused. The mass is then to be treated with 
diluted muriatic acid till every thing soluble is taken up, the filtered solution 
evaporated to dryness, the dry mass moistened with muriatic acid, and again 
treated with water. If any thing is left undissolved it will be silica, and if any 
alumina be contained in the solution, it will be precipitated by ammonia, and 
may be collected, washed, dried, and weighed, as already described. The so- 
lution may also be tested for magnesia, and if any be present it may be sepa- 
rated by the process already explained. 

The former of these two methods is to be preferred as the simpler, though it 
will also require considerable care and attention. That whicli the sulphuric acid 
leaves behind must be washed, dried, heated to redness, and weighed. It will be 
found to consist chiefly of quartz sand, and finely divided siliceous matter. 

The accuracy and care with which the whole of these processes have been 
conducted is tested by adding together the weights of the several substances 
that have been separately obtained. If this sum does not differ more than one 
per cent, from the weight of the soil employed, the results may be considered 
as deserving of confidence. One of the points in which a beginner is most 
likely to err, is in the washing of the several precipitates he collects upon his 
filters. As this is a tedious operation, he is very likely to wash them, at first, 
only imperfectly, and thus to have an excess of weight when his quantities are 
added together — whereas a small loss is almost unavoidable. The precipitates 
should always be washed with distilled water, and the washing continued until 
a drop of what passes through leaves no stain when dried upon a bit of glass. 



No. VI. 

ACTION OF GYPSUM. — (See pages 333-3i.) 

In the text I have stated what appear to me the most probable effects which 
gypsum is fitted to produce upon the soil. Some of the numerous opinions that 
have been entertained upon this point are thus summed up by Hlubeck : — 

^' According to Kollner, the action of gypsum depends upon the power pos- 
sessed by lime to form with the oxygen and carbon of the atmosphere compounds 
which are favourable to vegetation ; according to Ritckcrt, it acts like any other 
food ; according to Mayer and Brown, it merely improves the physical proper- 
ties of the soil ; while, according to Rcll^ it is an essential constituent of the plant. 
Hedwig called gypsum the saliva and gastric juice of plants ; Humboldt , Gir- 
tancr, and Albert 'P/iaer considered it as a stimulant by which the circulation 
of plants is promoted ; and Ckaptal ascribed its action to a supposed power of 
supplying water and carbonic acid to plants. Damj regarded it as an essential 
constituent of plants, because it acts only where gypsum is wanting in the soil, 
while other English agriculturists have supposed it to promote fermentation in 
the soil. According to Laubender, it acts as an exciting power without mixing 
itself with the sap of the plant ; according to Liebig, it fixes the ammonia of the 
atmosphere ; and, according to Bracoymot and Spre7igel, it supplies sulphur 
for the formation of the legumin of the leguminous plants (the most probable 
view)." — Erndhrung der Pjlanzcn, p. 70, note. 

To the above extract I may add, that Mr. Cuthbert Johnson, so long known 
for his many valuable writings upon agriculture, in following out the above idea 
of Reil and Davy in a recent paper on the use of gypsum (Jour, of the Royal 

P 



40 ACTION OF GYPSUM, [Appendix^ 

Agr. Society, ii., p. 108,) has stated that a crop of clover or sainfoin contains IJ 
to 2 cwt. of gypsum per acre, exactly the quantity which the farmers of Kent and 
Hampshire find it useful to apply to their grass lands every year. This state- 
ment "affords a veiy simple explanation of the use of gypsum, and one which 
til first sight leaves nothing to be desired. But it proves too much, for it 
b apposes the whole of the gypsum which is laid upon the grass or clover 
field to be removed year by year in the crop, and makes no allowance either for 
the quantity which must necessarily be carried off by the rains, or for that 
which must be sometimes at least laid on in the form of farm-yard or other 
similar manure. Nor does the result ( f analysis confirm the above statement 
as to the quantity of gypsum contained in the crop of clover or sainfoin. By 
referring to page 220, it will be seen that 1000 lbs. of dry hay do not con- 
tain, on on average, more than 4 lbs. of sulphuric acid — equal, supposing it all 
to be in combination with lime, to Sf lbs. of gypsum. Or a crop of 1^ tons of 
hay contains the elements of about 30 lbs. of gypsum — only about a sixth 
part of what is usually added as a top-dressing to the land. 



No. VIL 

SUGGESTIONS FOR EXPERIMENTS WITH THE SOLUBLE SILICATES 
OF POTASH AND SODA. 

In the text (pp. 207 and 349,) 1 have had frequent occasions to refer to the pre- 
sence in the soil of the silicates of potash and soda, and to their supposed action 
in supplying silica to the stems of the grasses and of the corn-bearing plants. 
It would be interesting in a theoretical point of view, to ascertain, by experi- 
ment, more fully than has hitherto been done, how far the application of these 
substances to the growing crops would, as a general rule, improve or otherwise 
affect their growth. But as those experiments which have already been made 
(page 349), afford a strong presumption in favour of their economical value, 
it becomes a matter of practical interest also to investigate their apparent effects 
upon each of our cultivated crops. 

These experiments are placed within the reach of the practical farmer during 
the ensuing season, by the introduction of the above compounds into the 
market at a reasonable rate (page 363). I therefore subjoin a few sugges- 
tions for experiments with these silicates, in the hope that some of the many 
zealous and intelligent practical men, wiio are now directing their attention to 
the applications of chemical science to agriculture, may be induced to enter 
upon this field of inquiry during the ensuing spring. 

1°. In order to convey silica into the plant, it appears to be chemically indif- 
ferent whether the silicate of potash or that of soda be placed within reach of 
its roots. But as the silicate of soda can be manufactured veiy much cheaper 
than that of potash, it is desirable above all to try the effects of this compound 
— upon the grasses and corn-bearing plants especially. 

2°. But as in the ashes of most plants potash is found in larger quantity than 
soda, it is possible that the effect of the silicate of potash upon some soils may 
be so much greater than that of the salt of soda as to counterbalance the dif- 
ference of expense. Hence the propriety of extended trials with this com- 
pound also. 

3<^. But as in the ashes of all our cultivated plants both potash and soda are 
found, it may be that a mixture of the two silicates may act better than either 
alone. It will be proper, therefore, to apply such a mixture in different pro- 
portions, and to compare it effects with those of each of the silicates laid 
on singly. 



No. VIIL] OF THE SOLUBLE SILICATES OF POTASH AND SODA. 



41 



The first series of comparative experiments, therefore, would be as follows : 

The application may be from 1 cwt. to IJ 
cwt. per acre, laid on as a top-dressing in 
moist weather early in the spring. Or it 
may be mixed with a large quantity of wa- 
ter, and applied with a water-cart. In either 



Silicate of 
Soda. 



Silicate of 
Potash. 



H Silicate of I 
Potash, 

/^Silicate of I 
Soda. 



Nothing. 



;i Silicate of 
Potash, 

j^ Silicate of 
Soda. 



case it ought to be in the state of a fine powder. 

But although the above applications produce a bene- 
ficial effect upon the crops, it will not necessarily follow 
that the silica, which the silicates contain, has had any 
share in bringing about the good result. By mere expo- 
sure to the air for a lengtli of time the potash or soda of those silicates will absorb 
carbonic acid from the atmpsphere, and be converted into carbonates. The 
same will take place more rapidly still in the soil, where carbonic acid abounds 
This conversion of the alkali into carbonate will set free a large part of the 
silica — in a state it is true in which it is in some degree soluble in water (page 
206,) — but in whicn, nevertheless, it will find its way into the plant with 
much more difficulty than if it had remained in the state of a soluble silicate. 

Now as the carbonates of potash and soda are known to promote vegetation 
(page 328), — though even with these, sufficient trials have not yet been madie 
— it is possible, as 1 have remarked above, that a good effect may follow the 
application of the silicates, and yet it may be altogether due to the action of the 
carbonates which are formed by their decomposition. It is of consequence to 
ascertain if this really be the case, because the quantity of carbonates which 
would be formed by the decomposition of the silicates could be laid on directly 
at one half of the price at which the silicates can as yet be sold. 

The second series of comparative experiments, therefore, which it would be 
interesting to try, would be such as the following : — 

The quantities here indicated are by the acre — that 
of carbonate of soda is given so great, because this salt 
contains upwards of three-fifths its weight of water (see 
p. 215.) 

Another consideration ought not here to be omitted. 
Nature, as has been frequently illustrated in the text, 
feeds her plants with a mixture of many different sub- 
stances, and by the aid of such mixtures they always 
thrive the best. The full benefit of the silicates, when 
applied alone, will be experienced only when every oth- 
er ingredient which the plant requires is already present in the soil, and in suf- 
ficient abundance. But this can rarely be the case. Its success will be more 
sui'e, therefore, if it be applied in a state of mixture with other saline substances 
which are known to be more or less useful to vegetation, and which will not, 
upon admixture, decompose these silicates. Such are common salt and the 
sulphate and nitrate of soda. 

A third series of comparative experiments, therefore, might be made, in which 
from 1 to 1| cwt. per acre of the following mixtures might be applied : — 1°. 
Equal weights of common salt, of dry sulphate of soda, of nitrate of soda, and 
of silicate of potos/i ; 2°. Equal weights of the same substances, omitting the 
silicate of jootash ; 3°. Equal weights of common salt, oi dry sulphate of soda, 
of nitrate of potash, and of silicate of soda; and 4'^^. Equal weights of the same 
substances, omitting the silicate of soda, or substituting carbonate of soda in 
its stead. 

The sulphate of magnesia (Epsom salts) or of lime (gypsum) can not be 
safely used along with the silicates, as the magnesia or lime they contain may 
decompose the silicates — forming sulphate of potash or soda and silicate of 
magnesia or lime, in which the silica is insoluble, and could not, therefore, until 
a further chemical change took place, find its way into the roots of the plant. 



Silicate of 
Potash, 
1 cwt. 


Crude 
Potash or 
Pearlash, 

75 lbs. 


Silicate of 
Soda, 
1 cwt. 


Crystallized 

Carbonate 

of Soda, 

150 lbs. 



43 



EXPERIMENTS ON TURNIPS, 



[AppeiidiZt 



No. VIII. 

RESULTS OF EXPERIMENTS IN PRACTICAL AGRICULTURE, 
MADE IN 1842. 



I have much gratification in laying before my readers the results of a second 
year's series of experiments undertaken in consequence of suggestions thrown 
out in previous parts of this Appendix, or of opinions expressed in the body of 
the work. It is one of the numerous good results which have followed from the 
issue of these Lectures in a periodical form that I have the pleasure of incoi-po- 
rating in the same volume the results of experiments made during two succes- 
sive years. No one who studies with care the experiments which follow, and 
the few remarks I have appended to them, will hesitate in pi'onouncing them to 
be as a whole the most valuable contributions to accurate experimental agricul- 
ture ever hitherto published. The results are not all equally important, nor all 
equally instructive, but they are the first fruits of a new line of research, which 
will lead us hereafter to the discovery of important general truths. They show 
that practical men are now on the right road, and — spi'eading as scientific know- 
ledge now is among the agricultural body — I trust there is no fear of their here- 
after being prevented from pursuing it. 



A.— EXPERIMENTS ON TURNIPS. 

I. The first series of experiments was made with the view of obtaining an- 
swers to these two questions : 
1°. Wkat are the relative effects of different saline sicbstances upon the turnip crop 

under the same circumstances 1 and 
2°. How far may these substances be employed alone to supersede farm-yard, rtumurt 

in the culture of ttirnips ? 

Turnips grown in Salter's Bog.— Field furrow-drained and subsoil ploughed. Manures ap» 

flied partly in drills before sowing on 1st June, and partly as top-dressing on 28th July, 
842. The salt and nitrate of soda last applied were dissolved in water; the others applied 
dry. ?%e quantity of land in each plot was one-thirteenth of an acre. 



No. 



Description of 
Dressing. 



Manure applied. 



1st June. 28thJuly Total 



Nothing . 

Common Salt 

Common Salt 

Rape-dust 

Nitrate of Soda. , . 
Nitrate of Soda.. . , 

Rape-dust , 

Nitrate of Soda 

Sulphate of Soda. . , 
Sulphate of Soda. . , 
Sulphate of Soda. . , 

Rape-dust 

Rape-dust , 

Guano 



11 I Soot 



lbs. 

2 

67 
2 

67 
I 2 
' 2 

67 

67 

8 

bush. 

n 



lbs. 



6 
6 



6 

4 , 

67 

9 

bush. 

1 



lbs. 



8 

8 
4 

67 

134 

17 

bush. 

2h 



Produce 
weight 
of bulbs. 



sts. lbs. 

43 11 

23 

66 10 

36 6 

45 8 

35 12 

29 7 

39 12 

46 3 
61 6 



Remarks. 
The rest of the field, 
grown with farmyard 
manure, was a fair ave 
rage crop. Those expe 
rimented upon were a 
complete failure, owing 
partly, no doubt, to the 
severe drought of the sea- 
son, but chiefly to the 
want of farm-yard dung. 
The seeds brairded bad- 
ly, and the drills were 
blanky throughout. Few 
of the plants reached any 
size, and the best of them 
were inferior to the plants 
immediately adjoining 
sown at the same time, & 
similarly treated, except 
as respects the manuring 



The foregoing experiments were made at the suggestion of Lord Blantyre on 
the home farm, at Lennox Love, near Haddington, and have been reported to 
me, at his Lordship's request, by Mr. William Goodlet, under whose immedi- 
diate superintendence the whole were conducted. 

The reader will not suppose, because they proved what are commonly called 



No. VIII.] EXPERIMENTS ON TURNIPS. 43 

failures^ that therefore they are of no value. On the contrary, they so far satis- 
factorily answer the questions they were intended to solve. They show 

1°. That saline manures in that locality cannot economically take the place 
of farm-yard manure, even for a single season. 

2°. That saline manures are even hurtful in the present condition of the land, 
when employed alone — producing a smaller crop than if no manure had been 
applied at all, and some of them in a remarkable degree. This appears to be 
especially the case with common salt, which at the rate of 1 cwt. an acre reduced 
the crop of bulbs nearly to one-half of what was yielded by the unmanured por- 
tion of the field. It is still more striking that nitrate of soda applied at the same 
rate should diminish the crop though in a less degree than common salt — and 
that soot should almost kill it entirely, and that 15 cwt. of rape-dust per acre 
should produce scarcely any effect. In regard to guano, it was applied in too 
small quantity to do all the good of which it was capable had it been laid on 
more largely. If 6 or 8 cwt. instead of 1| cwt. per acre had been used, the crop 
would probably have equalled that obtained by the use of farm-yard manure. 

There is no doubt that to the extreme drought of the season, as Mr. Goodlet 
observes, must be ascribed the injury or actual lessening of the crop, in this case, 
by the use of saline manures. The drought brings up the saline matters to the 
surface, and thus enables it to encrust, and weaken, or entirely kill, the growing 
plants. The want of rain in 1842 was much more felt in the Eastern part of 
Scodand than in the West, where the greater part of the succeeding experi- 
ments were jnade, and where occasional showers refreshed the land. 

One other observation I may make. Had the saline matters been mixed 
with a fair proportion of farm-yard manure, it is probable that even on this field 
the effects would have been very different. One reason for this expectation is, 
that the plants being kept in a rapidly growing state — partly use up, and even 
eagerly appropriate, a large poi'tion of the saline matter as it rises to the surface 
— and by their strength are enabled to resist the injurious action of any excess, 
which in ordinary circumstances is likely to remain. The reader, however, 
will not ask why the experiments were not so made — for he has already seen 
that their object was to ascertain the effect of saline manures applied alone. 
From their results, however, he will draw for himself the important practical 
rule, that in ordinary circumstances it is unsafe to trust his turnip crop to saline 
manures alone — that they may assist the action of farm-yard or other similar 
mixed manures, but cannot supply their place. But upon this point the suc- 
ceeding series of experiments throw much further light. 

II. The special object of the following four series- of experiments was to as- 
certain — , 

1°. The relative effects chiefly of various mixed, manures upon severed varieties 
of turnips ; and 

2°. Whether any of these mixtures could alone be economically used to supersede 
farvi-yard manure. 

They were made at the home-farm at Barochan, near Paisley, under the 
direction and superintendence of Mr. Fleming, whose excellent experiments, 
made in 1841, are recorded in a previous part of this Appendix (pp. 17 to 24). 
Mr. Fleming describes himself as much indebted to his overseer, Mr. Gardiner, 
without the aid of whose zeal, intelligence, and careful superintendence, so 
numerous a body of experiments could neither have been made, nor the results 
accurately ascertained. 

1°. Comparative Experiments with various substances nsed as manures, for growing 
Swedish Turnips : seed sown 6th June, bulbs lifted 25th Nov., 1842. 
Remarks— The land is a light loam, loose in texture, and of a light brown colour. Sub- 
soil hard, and full of small stones : it is of as nearly as possible the same quality. The tur- 
nip seed was all sown upon the same day. Rain came on the night after sowing, and in 
consequence the crops brairded well, and came away stronj. Those which show the great- 
est weight in the Table kept the lead of the others all the season. The numbers of the 
plots in the Table are placed in the order in which they followed each other on the ground. 
The crop would probably have been larger had there been more rain. 



44 



EXPERIMENTS ON TURNIPS. 



[Appendix, 



No. 


1 

ORCHARD FIELD. 

Description of Manures used. 


Quantity 
applied 

per 
imperial 

Acre. 


Produce 

of Bulbs, 

topped <St 

tailed, per 

imp. Acre. 


Produce of 

Bulbs, topped 

and tailed, per 

imperial 

acre. 


Cost of Manure 
per imperial 

Acre,including 

carriage and 

putting on. 


I 
2 


Peat and Night-soil, mixed 

Gypsum 

Carbonate of Lime 


20 tons. 

5 cwt. 
20 bush. 

1 cwt. 
20 bush. 
20 bush. 

6 lbs. 
50 bush. 
50 bu,sh. 
10 cwt. 
10 cwt. 
50 bush. 
10 cwt. 

3 cwt. 
3 cwt. 
3 cwt. 

50 bush. 

50 bush. 

50 bush. 

50 bush. 
50 bush. 
40 bush. 

1 ton. 

1 ton. 
20 tons. 


lbs. 

4800 
4080 
4640 

( 4320 

3980 
4400 
4240 
5920 
5560 
4800 
5200 
4960 
4080 
6560 

4240 

4480 

4400 

3200 
3600 
4160 
4000 
3920 
5200 
3440 


tons, cwt 
17 2 

14 11 

16 11 

15 8 

14 13 

15 14 
15 2 
21 2 
19 17 

17 2 

18 11 

17 14 

14 U 
23 8 

15 2 

16 
15 14 

11 8 

12 17 
14 17 
14 5 
14 

18 11 
12 5 


2 
2 

2 

1 
1 
3 
3 
1 
3 
3 
I 
2 
2 

3 



1 

2 
1 
I 
3 

2 
3 


£. 
6 



1 



2 
2 
2 
2 
3 
1 
1 
3 



1 
1 


1 

5 

8 

9 

10 


s. 
12 
12 
3 

12 

2 
15 
10 
10 


10 


10 

4 
15 

15 



17 

9 

5 

10 

10 

9 

10 


d. 

6 















9 



6 

9 


10 




r 


Sulphate of Ammonia 


3) 


Quicklime 




Soot 


4 
5 

6 

7 

8 

9 
10 
11 
12 
13 

14^ 

15 

:a) 

17 
18 
19 
20 
21 
22 
23 


Sulphur 


Imitation of Daniel's mixture.. 

Wood Charcoal Powder 

Fresh Animal Charcoal 

Exhausted Animal Charcoal. . . 
TurnbuU's Humus 


Bones diss, in Muriatic Acid. . . 

Baroclian Artificial Guano 

TurnbuU's do. do 

Natural Guano 


Salt and Quick-lime, mixed, ) 

3 months old ( 

Soot 


Potash and Lime mixed, 14 ) 

months old \ 

Quicklime 


Wood-ashes 


Bone dust 


Rape-dust 




Farm-yard dung 





Notlnng 











2°. Results of Experiments with various Substances used as manures for growing Z7ar/y 
Liverpool Yellov) Turnips, sown 9th June, and lifted 2d December, 1842. The quantity of 
land, in each plot was one-eighth of an imperial acre. 



No. 



14 



BERRIE KNOWES FIELD. 

Description of Manures used. 



Natural Guano at 25s. , 

Wood-ashes '. , 

Barochan Artificial Guano , 

Wood-ashes 

Rape-dust , 

TurnbuU's Artificial Guano , 

Wood-ashes 

Soil simple 

TurnbuU's Humus , 

Bone-dust 

Potash & Lime mixed, 14 mos. old. , 

Salt & Lime mixed, 3 mos. old , 

Sulphate of Magnesia ,. , 

Sulphate of Ammonia , 

Nitrate of Soda , 

Sulphate of Ammonia 

Wood-ashes 

Nitrate of Soda , 

Sulphate of Magnesia 

Wood-ashes 

Sulphate of Ammonia 

Sulphate of Magnesia 

Lime and Potash 

TurnbuU's Artificial Guano 

Barochan Artificial Guano 

Soil simple 



Quantity of 
Manure ap- 
plied per im- 
perial Acre. 



5 cwt. 
20 bush. 

5 cwt. 
20 bush. 
15 cwt. 

5 cwt. 
20 bush. 

50 bush. 
30 bush. 
50 bush. 
50 bush. 

1 cwt. 

1 cwt. 

1 cwt. 
56 lbs. 
40 bush. 
56 lbs. 
28 lbs. 
40 bush. 
84 lbs. 
40 lbs. 
20 bush. 

5 cwt. 

5 cwt. 



Cost per Acre, 
including • 
carriage and 
putting on. 



£. s. 

6 5 

10 

2 10 

a 10 

6 10 

2 1 

10 



1 17 

1 

8 

1 1 
1 5 

11 

1 
12 

2 

1 
16 
3 
8 

2 1 
2 10 



Produce of 
Bulbs, topped 
and tailed, per 
imperial Acre. 









tons. 


cwt 


qrs. 


32 


2 


2 


21 


2 


3 


24 


11 


2 


18 


5 


3 


11 


8 


2 


13 


14 


1 


17 


2 


3 


14 


5 


3 


18 


17 


1 


14 


17 


1 


24 


11 


2 


27 


2 


3 


20 


17 


2 


11 


11 


2 


16 


14 


1 


21 


4 


I 


24 


2 


1 


12 


17 


1 



No. VIIL] 



EXPERIMENTS ON TURNIPS. 



45 



Remarks. — The soil is a light hazel loam incumbent upon sand-stone rock. It was 
trenched with the spade, in the spring of 1842, out of pasture grassj to the depth of 16 inches, 
and the I'ock quarried out when it came nearer the surface than that depth, it was again 
pointed over before sowing, after which the drills were made upon the flat surface with the 
hoe, at the distance of 27 inches between them, (he manure sown in by the hand, and co- 
vered up, the seed sown and rolled in. The weather was very dry at the time they were 
sown, and continued so till about the 20th June, accompanied with east winds and bright 
sunshine. They brairded moderately well, and most of them came away strong and 
healthy. In examining them, and in the working them, which was done by the hand-hoe, 
many of them showed a remarkable difference from the others ; particularly No. 1 was pi e- 
eminenf above the others for size of bulbs and strength of foliage. Many of the bulbs were 
11 lbs. in weight; those with the saline and alkaline manures, such as Nos. 8, 9, 10, and 1^ 
were much smaller in bulbs and leaves than No. 1, but were remarkable for firmness ana 
solidity of bulbs. No. II was larger in size both of bulbs and leaves, but soft and light in 
weight. No. 7 had very firm solid bulbs, as had also Nos. 2 and 4. The numbers of the 
plots given in the Table indicate the order in which they were grown in the field. 
The Barochan Artificial Guano consisted of 

Bones dissolved in Muriatic Acid 2 cwt. I Nitrate of Soda 28 lbs. 

Charcoal powder 2 cwt. [Sulphate of Soda and ^ . 10 lbs 

Sulphate of Ammonia v. 1 cwt. I Sulphate of Magnesia \ "'" 

Common Salt and Gypsum, each 1 cwt. | ■ — — 

Wood-ashes 5 cwt. | I2cwt. 1 qr. 201bs. 

See note to page 47. 



3°. Experiments with various Manures on nine Acres of Turnips on the Farm 

at Crooks, 1842. 



6 


Date of 
Sowing. 


Quantity 

of Laud 

per Scotch 

acre. 


Manures, and quantities applied to 
the land sown, per Scotch acre. 


Produce 

in Tons 

per Scotch 

acre. 


KiAds 

of 
Turnip. 


Value 
of ma- 
nures 
applied. 


1 

2 
3 
4 
5 
6 

7 

8 


May 28. 

May 30. 

June 6. 

June 11. 

June 15. 

June 17. 

June 28. 
July 4. 


A. 

1 

1 

1 



1 

I 

1 
I 


R. 
1 


2 
3 

I 

1 

1 


Rape-dust 5 cwt.. Humus 25 bushels. 
Bone-dust 12 bushels. Peat ashes 5 
carts 


22 

20 

24 

19 

20 

IS 
14 
12| 


Swedes. 

Do. 
Yellow. 

Do. 

Do. 

Do. 

jyo. 

White. 


£. s. 

4 15 

4 10 

10 15 

10 

3 5 

2 15 

4 2 

5 12 


Rape-dust 5 cwt.. Bones 10 bushels. 
Humus 25 bush.. Ashes 5 carts. . . . 

Johnstone town-dung 30 tons at 6s., 
Bones 14 bush, at 2s. 6d 


Farm-yard dung 25 tons at 7s., Bones 
10 bush, at ^'s. 6d 


Artificial Guano (No. 1., p. 50) 2 cwt.. 
Humus 40 bush.. Peat ashes 5 carts. 

Natural Guano I cwt , Humus 40 
bushels 


Humus 57 bush., Bones 10 bush 

Artificial Guano mix., (No. IL, p. 50.) 



Remarks.— No. 1. Soil a stiff loam, moist, and in good order ; when the seed was sown 
it brairded well, and came away at once. 

No. 2. Soil rather lighter than the former; seed brairded well, and came away at once. 

No. 3. Soil the same as above ; brairded quickly in consequence of a shower of rain. 

No. 4. Soil lighter than No. 3 ; a bad braird, and turnips long of springing for want of rain 

No. 5. Soil as above ; long of brairding in consequence of want of rain. 

No. 6. Soil as above ; and like No. 5, still very dry for want of rain ; a late braird. 

No. 7. Soil lighter, mixed with peat; no rain— bad braird. 

No. 8. Soil heavy clay loam ; no rain, and a bad braird. 

The two latter, from drought and late sowing, did not grow much till the end of Sep- 
tember ; and when checked by frost in the beginning of November, were still growing 
vigorously. 

N. B.— The land was of different quahties, the seed also sown at different times, and in 
very different states of the atmosphere, with respect to moisture, yet the average produce 
was good ; and although it is not easy to say which of the artificial manures, imder such 
circumstances, was actually the beet, the general result shows that any of these used will 
produce on my land a good average crop of turnips, and at a less expense than farm-yard 
manure, and tends to confirm the correctness of various experiments tried by me on a 
smaller scale. The measurements having been made by the Scotch chain, I have not al- 
tered them. No. 8 would probably have been the best turnips, had they been sovm earlier, 
and been assisted by a fall of rain. 



46 



EXPERIMENTS ON TURNIPS, 



[Appendix, 



4°. Results of Experiments with different mixed manures, in growing White Globe Tur- 
nips, on new trenched land, Bucklather Field. Sown 13lh July, and lilted 16th December, 
1842. 



6 


Description of Manure used. 


Quantity 

per 

imperial 

Acre. 


Price of 

Manure 

per 

Acre. 


Weight in 

imperial 

pounds pr. 

>^th Acre. 


Weight in; 
Tons, «&c.' 
per impe- 
rial Acre. 


1 

2 
3 
4 


TurnbuU's Humus 

TurnbuU's improved Bones 

Barochan artificial Guano 


60 bush. 
5 cwt. 
5 cwt. 
5 cwt. 


£. s. d. 
3 

1 10 

2 10 
6 5 


lbs. 

5950 

4900 

6300 

9170 


tons. cwt. 

21 '6 
17 10 

22 10 
39 15 


Natural Guano 















The Natural Guano was purchased December, 1841, when the price was JE25 per ton. It 
can now be had for £12. 

Remarks. — The land was trenched 18 inches deep, and completely drained at the dis- 
tance of 18 feet, with tile drains laid 30 inches deep, in Feb. 1842. Previous to this it was in 
a wet, sour stale. It was again pointed over with the spade, and the drills made for the 
manures with the hoe upon the level surface. The manures were then sown in the bottom 
of the drills with the hand, and a little earth being put over them, the seed was sown, 
covered, and rolled. The weather had been dry for some time before sowing, but rain 
came on that day , they brairded quickly, and continued to grow till lifted — the field being 
well sheltered. The tops of Nos. 2, 3, and 4 were of a dark green colour, and remarkably 
luxuriant, many of the bulbs weighing from 5 to Ribs. No. 1 was of a lighter green, but 
strong and healthy, and many of the bulbs of this lot were 5 and 6 lbs. The bulbs of all of 
them were finely shaped. 



Ill, The object of the two following series of experiments was the same as in 
those of Mr. Fleming. 

1°, Results of comparative experiments upon Swedes and other Turnips made 
on the home farm of Mr. Alexander, of Southbar, near Paisley, in 1842. 

The soil of the field was a deep loam, with a slight admixture of peat — the 
subsoil was partly a Hght clay and partly a sandy gravel. It was thoroughly 
tile-drained and subsoiled to the depth of fourteen inches. 



No. 



Kind of Manures. 



Quantity 

per 

imperial 

Aqre. 



Swedes, sownSth May. 

Bone-dust 32 bush. 

Bones 16 bush. 

Ashdung 12 tons. 

Farmyard dung 32 tons. 

Mixture of Yelloip Sf White, soicn 2Qth July, j 

Guano 3^ cwt 

Guano i 2 cwt. 

Farmyard manure 8 tons. 



Cost per 

imperial 

Acre, 



£. s. 

4 8 

5 8 
11 4 

3 10 

4 16 



Produce 

in bulbs 

per imp. 

Acre. 



24 tons. 
28 tons. 
30^ tons. 

20 tons. 
24 tons. 



Mr. Alexander adds, I must here notice particularly the result of the last two experi- 
ments. The see'd sown was a mixture of yellow and white, and the period of sowing as 
late as the 10th July. The weather at the time being favourable, they brairded quickly, 
grew with great vigour, and when all the other turnips in the field became affected with 
mildew they stood as green as ever. This (viz., the non-mildewing) I attribute greatly to 
the guano, as well as to the late sowing, never before having seen such a weight of turnips 
produced, sown so late in the season. I applied other artificial manures on both of these 
fields with a due proportion of dun?, varying the quantities and modes of application, as ap- 
peared to me best to test their qualities, but as the comparative effect is so diflBcult to decide 
upon, I can only here observe, with any certainly, that though the turnips brairded quicker 
when the dung was assisted with these manures, particularly where TurnbuU's humus teas 
applied, the crops afterwards did not appear tome to be mateiially aided. 

2°. Result of experiments upon Yellow Turnips made by Mr. Alexander, of 
Southbar, at Wellwood Farm, Muirkirk, Ayrshire, 1842. 

The nature of the soil on which the experiments were made was reclaimed moss 
("then about 2 feet deep), having a clayey subsoil, but which had been thoroughly 
arained with tiles at fifteen feet apart. The field had produced white and hay 



No. VIII] 



EXPERIMENTS ON TURNIPS, 



47 



crops, but, as far as known, had never been previously green-cropped. The whole 
of it received the same labour, preparatory to sowing, and the weather during the 
operation ('which lasted four days) was the same, thus giving to each experiment 
an equal chance. The period of sowing was from the 15th to 19th of May ; the 
turnip seed used was Skirving's improved purple-topped yellow ; the dung used 
was the produce of the farm, and, with the exception of the foreign guano, all the 
other manures applied were those manufactured and sold by Mr. Tumbull, of 
Glasgow. The extent of ground for each experiment was one acre, Scotch measure. 



No. 



Kind of Manure. 



Farm-yard Dung. . 

Humus 

Farm-yard Dung. . 

Humus' 

Artificial Guano... 
Farm-yard Dung. . 
Prepared Bones'.. 
Farm-yard Dung. . 

Humus 

Improved Bones. . 
Artificial Guano.. . 
Ammoniacal Salts. 
Artificial Guano... 
Guano 



Quantity 

per 

imperial 

Acre. 



12 tons. 

2cwt. 
12 tons. 

If cwt. 

U " 
12 tons. 

2i cwt. 
12 tons. 
90 lbs. 
90 " 
90 " 
45 " 

3i cwt. 

3| " 



Cost of 
Manure 
per impe- 
rial Acre. 



0? 



£. s. 

4 4 

8 

4 4 

7 

6 

4 4 

15 OS 

4 4 -O-] 

3 9 1 

4 10 

5 6 

8 

1 3 
3 5 



Produce 
in Bulbs 
per impe- 
rial Acre. 



28 tons. 
24 « 
20 " 

16 " 



9i « 
28 " 



Cost for 
Manure 
per ton. 



s. d. 
3 3J 



1 

m 

7h 



IV. Ef'ect of Gypsum on the Turnip Crop. 

In 1841, Mr. Burnet of Gadgirth, near Ayr, applied a top-dressing of gypsum 
to part of a field of turnips, and found that it nearly doubled the crop. 

In 1842, Mr. Campbell, of Craigie, in the same neighbourhood, "dressed a 
six acre field, with the exception of a few rows, with two cwt. of unburned 
gypsum per acre. The crop over the whole was excellent, but there was no 
perceptible difference between the dressed and the undressed part." 

How are these discordant results to be reconciled 1 The following questions 
suggest themselves as worthy of investigation — 

1°. Is gypsuvi really propitious to the turnip crop, — and to every variety alike? 

2°. Are the unlike results above obtained to be ascribed to the abundant pre- 
sence, in the one case, of gypsum in the soil, or in the manure ploughed in, 
and its absence in the other — or to the variety of turnip cultivated 1 — or 

3°. Can the sea-spray supply gypsum to Mr. Campbell's estate, which is 
within two miles of the coast, while it is less bountiful to that of Mr. Burnet, 
which is six miles inland 1 



B.— EXPERIMENTS ON POTATOES. 

I. Results obtained by Mr. Campbell, of Craigie. 

Four equal drills of potatoes were treated as follows : — 

J°. Guano, 3 cwt. per aCre produce 5 pecks. 

2°. Farm-yard dung, 40 cubic yards per acre . , . produce 6 do. 
3°. Do., top-dressed afterwards with 60 lbs. of nitrate of soda, produce 6 do. 
4°. Do., top-dressed with 160 lbs. sulphate and nitrate, mixed, produce 6 do, 

* TurnbulVs Humus is formed from urine and night-soil mixed with gypsum and char- 
coal and then dried. 

TurnbuW 8 prepared Bones are bones and flesh dissolved in muriatic acid, and mixed 
with about an equal quantity of charcoal in powder. 

TurnbulVs Artificial Guano is, I believe, prepared bone.s, with a little salt and sulphate of 
ammonia prepared from urine, and dried with a stove-heat. 



4b 



EXPERIMENTS ON TURNIPS. 



[Appendix^ 

The above result is favourable to guano, considering that it was applied in 
such small quantity ; but why did the saline manures produce no effect— was 
It because of the drought of the season, or was it because Mr. Campbell's land 
IS already amply supplied with salts of soda from its vicinity to the sea^ (see 
Lectures, pp. 344 and 346). These experiments are not unworthy of repetition 
on a larger scale. 



II. Some very striking results, obtained by top-dressing potatoes with saline 
manures on a small scale, were described by Mr. Fleming, of Barochan, in 
1841, and are recorded in the preceding part of this Appendix (p. 20). The 
following three series of experiments, made under the direction and superin- 
tendence of the same gentleman, have been made upon a larger scale, and with 
the view of throwing light upon a greater number of interesting points— 

1 he object of the first series was to ascertain the effect — 

1 . Of different mixed manures, when applied alone to the potato cr&p. 

Z . Their relative effects 07i different varieties of potato. 



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No. VIII.] 



EXPERIMENTS ON POTATOES, 



40 



2°. The object of the two following series of experiments was to ascertain — 
1°. The relative effect of different saliTW substances applied along with farm-yard 
manure ; and — 2°. Whether the effects were greater when mixed with the ma- 
nure at the time of planting, or \Yhen subsequently applied, as a top-dressing ^ to 
the growing plemts. 

1°, Result of Experiments with saline substances in top-dressing Early American 
Potatoes. Planted 18th April, top-dressed 1st June, and lifted 28th Sep- 
tember, 1842. Low Field, Barochan. The quantity of land in each plot 
ivas one-eighth of an imperial acre. 













Cost of 


1 




Quantity 


Produce 


Produce in 


Produce in 


dressings pr. 




Description of 


of dressing 


in pecks 


bolls of 5 


tons, &c., 


imp. acre, 


JNo. 


Top-dressing. 


applied 


of 35 


cwt. each 


per imperial 


including 






per 


pounds 


per imperial 


acre. 


carriage and 






imp. acre. 


each. 


acre. 




putting on. 




cwt. 


pecks. 


bolls. 


tns. cwt qrs. 


£. s. d. 


1 Nitrate of Soda 


U 


128 


64 


16 — — 


1 11 


2 Sulphate of Ammonia. 


^ 


116 


58 


14 10 — 


1 11 


3 Sulphate of Magnesia.. 


It 


106 


53 


13 5 — 


12 6 


4 Nitrate of Potash 


148 


74 


18 10 — 


2 3 


5 Nothing Jjut Dung 


40 cubic yds. 


98 


49 


12 15 - 





f.^ Sulphate of Soda 

°? Nitrate of Soda 


1( 


144 


72 


18 — — 


14 9 


7 Sulphate of Soda 


2 


90 


49 


12 15 — 


15 


g^ Sulphate of Soda 

( Sulphate of Ammonia. 


'M 


151 


75^ 


18 17 2 


I 4 9 


q5 Sulphate of Magnesia.. 
/ 1 Nitrate of Soda^ 


i ( 


ISO 


90 


22 10 — 


1 9 



Remarks.— The soil is a light loam of good quality, subsoil hard,stoney till, and retentive 
of water. The potatoes were planted with the spade at the distaJice of 26 inches between 
drills. The manure, farm-yard dung at the rate of 40 cubic yaxds per acre, spread in the 
bottom of the drills — cutsets laid on this and covered up. (The cut tubers planted were 
the produce of those top-dressed last season (see Appendix, page 20). Came away strong 
and healthy, of a dark green colour, and were very remarkable from the contrast which 
they presented to the .'ame variety of Potato — planted alongside this experimental ground 
— tliat had not been dressed last season. These Iflst came away weak, and of a yellowish 
green colour, and, under the some treatment in every respect, did not produce so good a 
crop by 15 bolls per acre). Nos. 1. 2, 4, 6, 8, and 9, had all the same effect in altering the 
colour of the stems and leaves to a darker green. Nos. 3 and 7 had not that effect, but No. 
3 added greatly to the produce. No. 7 made no visible aV^eraLtlon, but burned the tops se- 
verely at the time of dressing, as did most of the otheTS this dry season ; this burning was in 
most cases only temporary. 

2°. Results of Experiments with different saline sub.<:tances, viixed with farm- 
yard dung at the time of planting, in growing Early American Potatoes. 
"Planted 29th April, and lifted 31st August, 1842. The quantity of land in 
each plot vnis one-eighth of an imperial acre. 













Cost of Salts 






Quantity 


Produce 


Produce 


Produce 


used, per 




Description 


applied per 


in pecks 


in bolls, of 


in tons, 


acre, inclu- 


No. 


of Manure and Salts. 


imperial 


of 35 lbs. 


5 cwt. 


&c., per 


ding putting 


1 


acre. 


each. 


each, per 


acre. 


on,exrlusive 


1 






acre. 




of Dung.* 


I 




Pecks. 


Bolls. 


Ins. cwt. qrs. 


£. s. d. 


1 Farmyard Dimg alone. . 


35 cubic yds. 


71 


35^ 


8 17 2 




2 Com Salt, added to Dung 


2 cwt. 


70 


3fa 


8 15 


4 


3 Nitrate of Soda, do. 


li " 


99 


49| 


12 7 2 


1 12 


4 Snlph. of Magnesia, do. 


2 » 


91 


U 7 2 


17 


5 Sulph. of Ammonia, do. 


U" 


107 




13 7 2 


1 12 


6 Sulph. of Soda, do. 


2 « 


64 


32' 


8 


17 


7 ; Silicate of Potasht do. 


1 « 


120 


60 


15 





' Dung 5s. 6d. per cubic yard, exclusive of cartage and spreading. 

t The silicate of potash or soluble glass was directly prepared from caustic potash and 
sand or silex fused together. 

D 



50 



EXPERIMENTS ON POTATOES, 



[Appendix, 



Remarks. — The soil upon which the above were grown was a subsoil, the upper soil 
having been taken off at different times. It was trenched two fspt deep in the fepring of 
1841, and wnjch had to be done with the mattoclt, it being too hard for the spade alone, it 
was cropped that season with potatoes, manured with 40 cubic yards of compost of weeds, 
cut grass, and half-rotten leaves. It was again trenched to the same depth after the crop of 
potatoes was lifted j and was again planted in the Spring of 1842 with potatoes, manured 
with 35 cubic yards of farm-yard dung, mixed in the proportions stated with the above salts. 
The potatoes were planted with the spade, at the distance of two feet between the drills, the 
manure being put in the bottom of the drills, the salts sown by the hand above it, and then 
all mixed together with a dung fork. The cut sets were laid upon the mixture, and covered 
up. As was remarked in 1841, the potatoes w^lh No. 3 were eight to ten days brairded be/ore 
the others ; also Nos. 5 and 7 were earlier than the others, those three being all/airly up in 
drills before the others made their apjjearance through the ground. Nos. 2, 4, and 6 were la- 
test, and very irregular in coming up, and upon examining the drills a few of the sets ap- 
peared to have been burned. There was a marked dissimilarity in the stems and leaves of 
these potatoes through the summer. Nos. 3, 5, and 7, were all of a darker green colour and 
Btronger than the others, fio. 7 was remarkable for intense7iess of colour and length of 
stems, so much so that it appeared to be a different variety of potato. JVo. 4 was fully bet- 
ter in appearance than Nos. 2 and 6, which were of a yellowish green colour and had a 
stunted appearEUice all the season. — When this ground was first broken up, a pound of it 
was boiled in pure rain water and filtered, which was then evaporated, the residue weighed 
4^ grains, mostly soluble salts, but hardly a trace of common salt. 

3°. The following experiments were made with the view of determining how 
far economical mixtures might be made to supersede farm-yard manure in the 
groiath of potatoes : — 

1°. Account of an Experiment in growing Potatoes (Irish Pink Eyes) with the following 
mixture of substances, instead of farmyard dung, planted 20th April, 1842. 



No. 


Ingredients. 


Quantity in- 
tended to ma- 
nure four 
acres. 


Cost of 
Substances 

for 
four acres. 


1 
2 
3 

4 
5 
6 
7 
8. 
9 
10 


Rape-dust.... 


cwts. qrs. lbs. 

5 
2 
2 24 
2 

2 

1 2 
1 2 
2 
2 

6 2 


£. s. d. 
1 10 
12 
6 
1 6 
10 
2 3 
9 
10 
1 


Bones dissolved in Muriatic Acid. 
Sulphate of Magnesia 


Carbonate of Lime 


Nitrate of Soda ^ 


Common Salt 


Sulphate of Soda 


Sulphate of Ammonia 


Sulphur 








20 26 


4 1 9 



Remarks. — The above mixture was sown in the drills at the rate of abotit 5 cwts. per im- 
perial acre, at a cost of little more than jBl. sterling, and produced a fair crop of potatops of 
a remarkably fine quality, 43 bolls per acre of imperial Renfrewshire measure, weighing 5 
cwt. each, upon a poor and light, although new soil, but not worth more than 25s. per af re. 
Great caution is required in using this mixture, as it is very apt to burn the cut sets if laid 
directly upon them. A little earth should be put between the cut potato and the manure. 

2°. The following mixture was made, and lay together for five weeks, when it was sown in 
the bottoms of potato drills upon a poor tilly soil, Eind White Don Potatoes planted with it 
30th April, 1842. 



No. 

1 
2 
3 
4 
6 
6 
7 


Ingredients. 


Quantity mixed 

to manure one 

acre. 


Cost of Sub- 
stances for 
one acre. 


Saw-dust, mostly from Alder 

Potash <fe Lime mixed, 14 mos. old 
Common Salt 


cwts. qrs. 

1 2 
1 
2 
2 


bush. 
40 
10 


je. s. d. 


7 6 

2 3 

1 
3 6 
4 
10 


Siilnhate of Ammonia 


Sulphate of Soda 


SulpliaXe of Magnesia 


Coal Tar, 20 gallons, say 




3 2 


50 


2 7 3 



No. VIII.] EXPERIMENTS ON POTATOES. 51 

Rkmarks. — The potatoes planfert with the above mixUire came quickly fhroneh the 
gVouiul, and were very liixiiriani in fuliaiie. Tliey were li!te<] 15tli October, after being cut 
down by frost whilst still unripe and wowing. On being taken up, they were Ibund to yield 
a produce oi 56 bolJs of Renfrewshire measuie, weighing 5 cwts. each, per acre, of very 
fine potatoes, many of which weighed from 24 to 30 oz. each. 

N. B — This mixture, alter being put together, fermented, cind was frequently turned, but 
kept dry. 

The several series of experiments made upon potatoes by Mr, Fleming are 
deserving of careful consideration, and many of them of judicious repetition. 
They are all well contrived or devised, and each series skilfully arranged. 

In agricultural experiments it is of the greatest possible consequence that the 
practical man should have a clear and definite object distinctly in view. If so, 
his experiments may be signally successful in his own estimation, while, eco- 
nomically considered, they may be total failures. This, as we have seen, was, 
to a certain extent, the case with the first series of experiments made upon Lord 
Blantyrc's form, as above detailed (p. 42). The applications in some instances 
lessened the crop, but the result, nevertheless, threw considerable light upon the 
questions which the trials were intended to solve. 

In making an experiment, the practical farmer asJcs a qitestion of nature; — in 
arranging the form and details of his experiment, he is putting together the 
words by which his question is to be expressed. If his question be clearly put, 
nature will give him, sooner or later, a clear and distinct aiiswer — if he have 
skill enough in nature's language to understand what she has said to him. I 
say, sooner or later, for it may be sometimes necessary to repeat the question, 
either because something has intervened to prevent nature, so to speak, from 
hearing his question, — because it has not been accurately expressed — or because 
somethuig in the seasons, or othei-wise, has prevented her answer from being 
clearly understood — perhaps from being heard or read at all. Circumstances 
may even prevent the answer from being given until a second summer come 
round, when, if we are not on the alert, it may never be received at all. 

The above experiments, as wdl as those which follow, form an excellent 
study for the practical farmer in reference to this matter, Eveiy series is plan- 
ned with a view to a given end, the circumstances are carefully noted before, 
during, and at the close of each of the several trials, and the answers are re- 
corded with a very praiir.eworthy degree of accuracy, I shall place together, in 
one view, the most important of the deductions to which the experiments of 
ISI'S appear to have led, when I shall have laid before the reader the whole of 
the tables which have as yet been placed in my hands. 

C— EXPERIMENTS UPON BARLEY. 

The object of the following experiments, also made by Mr, Fleming, was to 
ascertain the relative effect of different saline substances, when applied, as top- 
dressings, to a crop oftohife barky. 

The results, as shown in the last column, are sufficiently interesting. 

Results of Experiments with various substances used as top-dressings upon 
Barley (conmion white). The Barley sown 14th April, top-dressed 6th 
May, and cut down 2pth August, thraished, cleaned, measured, and weighed 
5th October, 1842. The n^iantity of land in each plot was one-eighth of an 
ivvperial acre. 

Remarks.— The soil of this field is a liaht loam, as nearly as possible uniform in quality, 
and I'.ad \.\m about ten years in pasture previouf? to the sprina of 18^12, when it was all 
trenclied with the spade twelve inches deep. It had been thoroujih-drained with tiles some 
years before breaking np. After beins trenched, it was dressed over, except where the ex- 
periments were, with two chaldrons of lime per acre, slaked with water, in which common 
salt ha.d been dissolved, and before sowing the barley, with the exception of the experiment 
ground, it v/as top dressed over with two and a half'cwts. of Turnbull's artificial guano per 
acrp, harrowed in, as was also the top-dressing No. 3 in the table of experiments. The bar- 
ley was sown hroadc?tst, 2h bushels per acre. Owing to the extraordinary drought at time 
of sowinu, it did not braird well till rain came ; aller which it made rapid progress. Advan- 
ffifie was taken of heavy rains to put on the top-dressings, all of which were sown at tho 
time above stated, vi^., 6lh May, except No. 4) vrhich Was not sown till the 17tb, at which 



52 



EXPERIMENTS UPON BARLEY. 



[Append-kc, 



No. 



RoDBN Hill Field. 

Description 
of Top-Dressings. 



a 



Nitrate of Boda 

Common Salt 

Sulphate of Soda 

Sulphate of Magnesia 

Natural Guano, at 25s 

Nitrate of Potash 

Common Salt 

Nothing 

TurnbuU's Artificial Guano.. 



O Oi 
3 C 



> !m O !•<.-!> CO 



(U 






; be s cQ 

ce 



lbs. 
1821 

1638 

2192 
1665 
1735 
1620 
1925 



lbs. 
364 

378 

432 
255 
378 
325 
334 



■acC c 



3 ^ 



lbs. 
500 

491 

589 
.590 
495 
425 
480 



lbs. 
56 

55 

54 
54 
57 
55 
54 



0.5 



s. d. 

2 n 



7 
6 
6f 



8 



c ^ 




.r CD 




Cja 




bi-^ 




^^ 




t^rt 


u 


sy 


o 


c ^ 




J«<2 


Q. 


C?tc 


S 


bush. 


lbs. 


52 





54 


54 


64 





37 


42 


53 


3 


47 


15 


49 


26 



time there teas little rain, and, in consequence, it burned the plants, of which they did not re- 
cover all the season, and the ground got full of weeds. No. 5 burned the plants also, but 
they recovered quickly, and gave a good return. As was remarked before, inherever common 
salt wasput on as a top-dressing on grain crops, either of wheat, barley, or oats, and on what- 
ever description of soil upon this estate, the grain was xii-varlably heavier per bushel, and had 
fewer weaks or tails in proportion to the quantity of grain per acre, than any of the other 
dressings applied here. From the frequent mention of spade culture in these experiments, 
many may consider that they were upon a very small scale, which is not the case, the 
greater proportion of them being very extensive. Mr. Fleming, to give employment to the 
destitute labourers, having dug and trenched about thirty acres of land instead of ploughing 
it, which accounts for the frequent mention of spade culture, which, when it can be got ex- 
ecuted at a moderate rate (particularly trenching at j£4. per acre), is very advantageous, 
and seems superior to trench ploughing. A. F. Gardinepw. 

D.— EXPERIMENTS UPON OATS. 

The first of the following series of experiments was made at Lennox-Love, 
at the request of Lord Blanty re, the second at Barochan, imder the direction 
of Mr. Fleming. The genei-al object of both was the same — to ascertain the 
relative effect of different saline substances applied as top-dressings iipon young 
oats ; but tliose of Mr. Fleming have, besides, the special object of ascertaining the 
effect of certain mixtures upon oats lohen grown upon mossy lav d. 

1°. Oats, second crop, after old lea. Soil sharp loam ; subsoil clay resting on sandstone 
rock. Oats sown 14th March ; (op-dressinzs applied 13th May; crop cut 27th Aug. ; and 
thrashed 9th Sept. , 1842. The quantity of land in each plot was one- eighth of an imperial acre. 







MANURES. 


C Oj 


Weight taken horn 


OJ . 


OT 




i'S 










Xhr^"!"'"" ^f'" '><" 


.^ c 










Quarry Park, 
Lennox-Love. 




o 




2 




O i»Al 










^^ 02 


No. 


Description of 










X 






Oj'-U 

a. <i- 


o 


2 = 


ce a 




• Dressing. 


go. 


ai 




CO 

03 


4, g 




« is 




go 


5 o «s 


^> ^ ^ 






/3 =»■ 


O 




Q 


G3 o 


V2 


o 5 


^'S 


& £ 


5^o 


C-oCS 






lbs. 


s. d. 


lbs. 


Ihs 


lbs. 


lbs. 


Ihs, 


lbs. 


bushs. 


bush. 


bush. 


1 


Nothing 


— 


— 


672 


264 


8 


362 


38 


39i 


6-75 


— 




2 


Common Salt 


14 


4 


588 


239 


13 


323 


13 


40 


6-00 


— 


•75 


3^ 

4 • 


Common Salt 

Rape-dust 


7? 
112 S 
14 


7 
3 1 


644 

588 


236 
205 


24 
21 


328 

276 


56 

86 


40 

39f 


5 95 
519 


— 


■80 
1-56 


Nitrate of Soda 


5^ 
6j 


Nitrate of Soda 

Rape-dust 


7? 
112^ 


8 7 
2 


616 

504 


231 

167 


17 
12* 


296 
266 


72 

38i 


40 
39 


5-56 
4-81 


— 


119 
1-94 


Nitrate of Soda. ... 
Sulphate of Soda. . . . 


7 


Sulphate of Soda. . .. 


14 


1 


504 


ISR 


11 


249 


56 


39i 


4-82 


— 


1-93 


sj 


Sulphate of Soda .. . 
Rape-dust 


7^ 
112 S 


7 5 


672 


263 


20 


355 


34 


40i 


6 56 


— 


•19 


y 

10 

11 


Rape-dust 


224 
28 
4 bush. 


14 U 
5 
4 


616 

938 
£32 


224 
351 
193 


26 
30 
11 


324 
496 
269 


42 
61 
59 


40i 
40J 
37-f 


5-62 

8-75 
512 


200 


113 
1-63 


Guano 


Soot 


Waste water from gas 


12^ 


work diluted with 4 


> 6galls. 


— 


700 


273 


15 


390 


22 


mi; 


7 00 


•26 





1 I 


times itsbuUt of water 


5 























No. VIIL] 



EXPERIMENTS UPON OATCS. 



53 



2°. Resulta of Experiments tmih various substances tised as top-dressings upon Oats (Sandy 
Oats), sown 16th April, upon drained peat moss. Nos. 2, 3, and 5 top-dressed on the same 
day ; No. 1 dressed 6th May, cut down 14th September, and thrashed, cleaned, and 
weighed 6th Oct,. 1842. TTie quantity of land in eachplot was one-eighth of an imperial acre. 



No. 



SHAW PARK FIELD, BAROCHAN. 

Description of Dressing. 



Sulphate of Ammonia j 

Water 

Sulphate of Soda 

Nitrate of Soda 

Bones dissolved in Muriatic 

Acid 

Nothing 

Sulphate of Ammonia 

Silicate of Potash 

Sulphate of Soda 

Bones dissolved in Muriatic 

Acid 



<3 



12i lbs. 
20galls. 
21 lbs. 
9§ lbs. 

[42 lbs. 

i 7 lbs. 
14 lbs. 
14 lbs. 

14 lbs. 



D.3 

.is 

c8 

lbs. 
!ll05 

il220 

1340 
960 



■ 1600 



'5 & _a) 



en 



lbs. 
270 

305 

320 
210 



350 



a 



Jbs. 
420 

450 

4R0 
320 

620 



lbs. 
41 

40 

42 
39 

43 



s. d. 
2 6 









3 6 

ri 41 

•|2 01 
U 2^ 

1. .1 



bush, lbs 
52 18 

61 



60 


40 


43 


3 


65 


5 



Remarks.— The soil upon which the above were grown is moss, rather deeper m some 
parts than others, incumbent upon gravel of a stiff retentive quality. It had been partly 
drained some years ago, but owing to the nature of the soil the drains did not act well. In 
the spring of 1842, it was again drained with tiles, and trenched over with the spade to the 
deptli of 16 inches, and some of the gravel subsoil brought up among the moss. The ground 
beiii'^ divided into lots for the purpose, the top-dressings Nos. 2, 3, and 5 were sown on the 
16th April, and slightly harrowed in ; the oats were then sown and harrowed in. No. I was 
made from 160 lbs. sulphate of ammonia dissolved in 100 galls, of water (proportions for an 
imperial acre) and sprinkled upon the oats during the time of rain on 6th May. No. 5 was 
sown upon a lot where the moss was fully the deepest. They all brairded well ; Nos. 2 and 
5 coming rather earlier than the others, and of a darker colour, particularly No. 2. No. I, 
after bein" watered with the solution, became also of a darker green, but neither Nos. I nor 
2 were so'stron-' in the straw as Nos. 3 and 5, both of which were remarkable for strength and 
luxuriance, especially No. 5, which kept the lead of the others all the season. 

E.— EXPERIMENTS UPON WHEAT. 
Th3 following three Experiments upon wheat exhibit very interesting results : 
1°. The first series was made on the home farm of Lord Blantyre at Lennox 
Love, and was intended to ascertain the relative effects in that locality of differ- 
ent, chiefly saline, manures applied as top-dressings to spring wheat. 



No. 



Lennox-Love. 

Description of 
Dressing. 



Nothing 

Common Salt 

Common Salt 

Rape-dust 

Nitrate of Soda. . .. 
Nitrate of Soda... . 

Rape-dust 

Nitrate of Soda. . 
Sulphate of Soda. . 
Suliihate of Soda. . 
Sulphate of Soda . 

Rape-dust 

Rape-dust j 224 

Guano I 28 

jSoot 14 bush. 




Weight taken from 
Thrashing Mill of 

c 



>»T3 

*> c 

CS u 

lbs. 

10 

20 

m 

20i 
171 

12 

11 

101 

14 
14 
14 



m 

lbs 
507 

547 

610 
598 
648 

595 

483 

514 

575 
566 
564 



•« C 
y 3 

lbs. 
154 ' 
92 

134^ 

138i 

116i 

107 
1151 

n6i 

116 
145 
97 






be I-. 

SO 



lbs. 
6U 
61i 

61i 

60f 

6U 

60f 

60 

61 

62i 
61i 
601 



■S't3 



bushs. 

5 9'56 
5-750 

6 250 
5970 
6-375 

6-000 

4-750 

5-562 

6-381 
6 000 
5-939 



71 a 
£•50 



bush. 

•29 

•014 

419 

•044 



•425 
•044 






S ^ S 

a? ^ s^ 

O-oO 



bush. 
206 



1-206 
•394 

•017 



54 



EXPER/MENTS UPON WHEAT. 



[Appendix, 



T»r^^!!1''''^-~?P""^ Y^r^^^ t^^^" Turnips, Soulh-Lawn. Soil loamy clay • siib<=oil clay 
Ma^ croD cut o^^^ „.^^k^S^?A^P 1'^ February, 1842; manures applied I3ih 

TdTh-vJ^lr!"^?^ f '^^ ^^■^°'?'^ f 'i''' "'^^^ '^* Barochan, was to ascertain the 
whiter wheat -^ '^'^^''''^ ''''^^'^'' "'^'"^^ ""^''''^ manures applied as top-dressings to 

^nri^^ir^ ?,k''^"""^"'^ ^^"^ various substances used as top-dressincs unon Winter Wheat 




Nothinsr 
Natural Guano 
TiinibuU's Artificial 

Guano 
Common Salt.. 
Suipl^iate of Sofia 
Nitrate of Soda 
Common Salt... 
Dissolved Bones 

Rape-dust , 

Sulphate of Masnes 



Remarks.— The soil is a heavy loam, incumbent unon a deen rlav Th«» ivh^of ,^ 
at the end of November, 1841, after a croo of vellmv inrnh.t^ T'hl'.. ' ^^^^ ^°^'" 

with 20 tons of town dung per t^^vl O^VxJ xSrsevS^^^ manured 

of 1842, the plants were very thin upon he -round In Anr^ll^pf,! ^^^^ 1""^ '"'''''"S 
grass seeds harrowed and i^olled, afte? whicMt t.lierJd a'nS^Sa l^? LreJed^'ltt^i 
time the dressings were put on there was rain, but in general Tv zra/^rv rSL^i^/^r ^w 
inconsequence the top-dressings did not. produce such great resul^Z %eydTdn\^['^li 
field was examined from time totime,Snd ihe appefrance of LTh eLeWmelfas no^el 
down is fully borne out by the results given in the ta'ble, viz. :-No. 1 was taHe^in the s^raw 
^nger m the ear, and of a darker green colour than any of the others : No 6 was nprf fn^ 
No. 4 was third. In point of appearance there was in the others no nercerjtible ri^fferpnn^ 
from the general crop, except No. 3, which appeared to have checL^d^he growth of ?hf 
plants, and from this check they scarcely recovered all the season It is howeveTiemarka 
fclethat^wherever common salt was applied the grain was heavier per bushef 7S A^ 
observed, with reference to the experiment upon wheat grown on this land last year tZ.tthl 
application of common salt had a very great 'effect, and would probably hZeaTsofene'£ed the 
general crop this year, had it not been/or the extraordinary drought oftheseZn%7fl%en. 

3°. The object of the third series, made by Mr. Burnet, of Gadffirth near 
Ayr, was the same as those of Mr. Fleming. The mixtures employed ' how- 
and'sSact^^'^"'' ^^ tabulated results are at least equally interesting 

Resiilts of Experiments with mixed Manures used as top-dressings upon Winter Wheat 
(Eclipse variety) sown 29th October, 1841, and reaped 15th August, 1S42. TheouaS 
of land in each pbt was one fourth of ammperial acre. ^ ne quanmy 

KoT^^r" "^ loam, with subsoil of clay ; tile-drained an'd trench-ploughed. Had been in 
beans the year previous, and had no manure with that crop nor wi h the wheat except thS 
above applications, harrowed in in spring. No. 6, at a cost of £2. 4s. harnroduced En in 
crease over No. 1 of jE6. 19s. 3d. being a ^-am of 2^. 15s 3d proauced an m- 



No. VJIL] 



EXPERIMENTS UPON WHEAT. 



55 



— 














a) 


;-i 


_c 


_c 


c 
o 


2^ 




GADGIRTH, 
NEAR AYR. 


i 

q5 


d 
O 


o 


D 


• d 




a. 


0) 

3 

> 


> 


1 


2J 


d 


Manures applied 
16th April. 


o 

bj) 

'53 


o 

s 




'S 


"3 
O 

13 


-So 


-< VJ 




55C 


O c« 
o a. 


=^5 

§1 

lbs. 






cwt qrs lbs 


cwt qrs lbs 


cwt qr.s lbs 


lbs. 


Jbs. 


bshl. lbs 


L. 8. 


L. s. 


s. d. 


L. 8. 


1 


No application.. 


7 1 ISi 


4 3 23§ 


4 16 


61i 


9 


31 38 


11 1 


— 


— 


— 


98 


2 


Guano k cwt. & 


























Wocd-aslies.. .. 


7 2 18 


5024 


4 1 9 


61i 


10 


32 20 


U 6 


5 


— 


2 


88 


3 


Artificial Guano 
I cwt. & Wood- 


























ashes 1 cwt 


6 3 25 


5 17 


4 1 10 


59^ 


9 


32 24 


11 6 


5 


— 


1 12 


88 


4 


Sulpl). of Ammo- 


























nia ^ cwt., Wood- 
ashes Icwt 


8 3 21 


6 2 7 


5 1 lOi 


60 


17 


39 54 


14 


2 19 


6 3 


2 


85 


5 


Suiph. of Ammo- 
nia icwt., Snlph. 
of Soda 1 cwt., 
& Wood-ashes 1 
























6 


cwt 


11 ISi 


7 9i 


6 2 8i 


60 


13 


49 6 


17 4 


6 3 


16 9 


2 16 


81. 


Sulph. of Ammo- 




nia ^ cwt., Com- 


























mon Salt ^ cwt , 


























<fe Wood-ashes 1 
























7 


cwt •. 


11 1 4 


7 1 24 


6 2 6i 


60 


9 


49 


17 3 


6 2 


17 3 


2 4 


84 


Siilph. of Ammo- 




nia Ac wt., Nitrate 


















• 








of Soda ^ cwt.. 






















8 


& Wood-ashes 1 

cwt 


11 5 


7 23 


6 1 25 


59 


11 


48 20 


16 18 


5 17 


16 Ih 


3 4 


70 


TnrnbuU's Gua- 




no 1 cwt., Sulph. 


























of Lime 1 cwt., 










, 
















& Wood-ashes 1 
cwt 


80 6 


5 2 8 


4 2 2 


60 


23 


33 44 


11 16 


15 


23 


I 16 


81 



F.— EXPERIMENTS UPON PASTURE AND OTHER GRASSES. 

I. Experiments made by Mr. Alexander, at Wellwood, in 1842. 

A. On crops of meadow and rye grass hay. 

1°. One Scots acre of well-drained mossy meadow, and full of timothy grass, 
was top-dressed during the last week of April, with 1 cwt. improved bones, i 
cwt. glauber salts, § cwt of charcoal, all well mixed with ashes. Result.— 
Crop much improved, and came to 180 Ayrshire stones (of 24 lbs.) per acre. 
I may mention that this meadow suffered generally much from the severe 
drought; the above kept its growth best. ^„ ^. , 

2°. One Scots acre of well-drained mossy meadow, fuU of timothy grass, was 
top-dressed during the last week of April, with 1 cwt. of artificial guano, 12 
bushels of humus, well mixed with a quantity of ashes. R£SULT.--Not so 
good; more affected by drought; crop 160 stones per acre ; the rest of the un- 
dressed meadow land, on an average, 140 stones per acre. 

3°. Three acres of rye grass hay, upon a very light sharp soil, was top-dressed 
during the last week of April, with 3 cwt. of artificial guano, 2^ cwt. of improved 
bones 1 cwt. of charcoal, all mixed with a quantity of ashes. Result.---I can- 
not pronounce that the hay on the three acres was increased in bulk ; the crop 
was a light one on the whole field, owing to the severe drought, and the very 
dry nature of the soil this season, therefore, gave this experiment no fair trial. 
I would say, however, that I have rarely seen such an appearance of white 
clover since the hay was cut, and particularly on the dressed land. 



56 



EXPERIMENTS UPON PASTURE GRASS. 



lAppendiZf 



B. On pasture grass. 

.hrix&"! »T.i J»:„r"ionrr.' """^/t '™='--' ■'-wed i„.o 

No. 1. Dressed whhT™^? ^PP''¥ ''"""S *« loa week of April, 
(glauber stlts) ^ "'"^ * '="'• "^ '»»"'<'"Mcal salts, 1 cwt. of sulphate of soda 

of ^mmo?X^ "'* * °" of ^'"°»-'=«' -1'^, 4 owt. of glauber salts, J cwt. 
ofSat rfS' "" * °^'- of ^""""-l ^'"l'^, i cwt. of glauber salts, i cwt. 

.atfrwarquSS„ed'^„™11™red"'"f\"'"''' '",^" "'= "''^'= ^^^ "— S- 

produce cut, it is not easv to sav hnwTl fi u ,® ^^^^^^ season, and the 

the grass ; but certa nlv th^smal fieTdHiH ^^.°^' ^pphcation went to improve 
calvis nearly allJhe season wonders-for it pastured fifteen early 

MJ^S,fg"7 Birht"^^^^^^^^^^^ ''T, °^ «>^P-iments were made by 
mental wheat of 184^ was glSw/- ^ '''^' °" ''^" ^'^^ '""^''^ the expel 
^'^^^^'^^^^^^^^^^^^ 30th June, 1842, Crook's 



t 



No. 



'«! 



crook's farm, barochan, 
Description of Dressing. 



Nothing 

Sulphate of Soda. !."/." ' 

Common Salt 

Nitrafeof Soda ,'.'."" 

Sulphate of Soda. .. 
Nitrate of Soda, mixed.".*! 

Natural Guano 

Silicate of Potash '.' 

Gypsum * ' 

Sulphate of Ammonia. ! '. ' 

Turnbull's Guano 

Common Salt 

jSoot .'.'.*.'"" 

[Hay of BarleyL^nd', "ma- 
nured with Bone-dust. 1841 



C m 



" o ^ 



O.C Lc >, 



fl3 O ;. s_ 



B. t't 



C — 






1 bushel \ 



lbs. lbs. lbs 

11,360 - 195 

7,740 — 1163 

672i 10,960 — 176 

1125 18,100 6640 351 

515 8,240 - 186 

932^14,920 3560 256i 



^S^ 



757i!l2,12G 

820 13.120 
595 9,520 

795 12,720 



760198 

1760!225 

— 186 

1360 228 
3680 305 



275 
312 



5 13 2 

6 14 1 



April Nos. 3 and 4 showed an improflmlnTovpr thl^^r''*'^P'i,^'« ' ^"^ '« 'I'e lasrweek of 
week ofMay, and by the 7th KaTtreSte of ida'^^No''.^ ^li^^'^ ^^^^^ rainsThe fi.i, 
nie alteration of the colour to dark greeSd tlheiiS ^hnv^^^K^^ be seen at a distance by 

Sp. Kl'!? ? '^°T^ "« "^^'•''e alteration from the Sessed Nn' ^'^''' l"P"" 'hat day 
taller and of a dark green colour, and thicker swarripHlr'.. ^"- ^^^^ ^^e best of any • 
m coourbt ^^^. ^^^^^^ ^^^^ ^a ^"^^l^^ker swarde^. fojshd little or no aiieratln 

as did No. 1, m being nearly all Festuca Rubra fw/AT^f,^^^'^*^ '^^'^orkable appearance 
grass, viz, (Festuca Rubra),^,zon/SL^oirn,K,t.'''"'^^ "ny rye-grass, altho^hof& 
othy, and red clover. No. 5 darker thin No U tfui ^^"'"^ *^^" *'°"'" *^'/A rye grasf t£i 

t^he 'smhh.^'1^ ,5'JV'' ^"^ ^0, wer'e d'rSsed a'pon he 7?S'Ma"v ^ tS ' '"^ ^"^ ^ ^-T^Vlm- 
the stubble of 1841 found that the ridges which vvpiPfnnHl^.-.,^^^ °^^" in ploughing up 

"1^.r;o/"StS'-^sti;'"hLre^?,fda"l^ l-vin^l!e'en"dViSr'''^^ ^^^^^^ ^-'^' '^^- "- 
ral Guano, 25s. percwt ArtlfiriHlAI^P^'"^'^'- Nitrate of soda, jEl. per cwt • lV«t„ 
15s. PercW; s'ulph\"hflmm"^i?,TL'plrc'w?.'^'' «"^<^^^«°f Potalh oS^bieS; 



No. VIII.] EXPERIMENTS UPON MIXED CROPS. 57 

G.— EXPERIMENTS UPON MIXED CROPS. 
The following interesting experiment was made by Mr. Alexander, for the 
purpose of ascertaining the effect of a mixture of gypsum and common salt upon a 

mixed crop of oats, beans, and peas : — 

Result of an experiment upon the effect of gypsum and common salt, applied 
as a top-dressing at Wellwood, Muirkirk, 1842. 

Four Scotch acres of strong soil, bordering on clay, broken up from two-year- 
old pasture, were sown with oats, beans, and peas (which is called in Scotland 
mashlem, and is a first-rate fodder for dairy stock). They all came well up, but 
woi*ming and other causes injured the crop so much that I had serious intention 
of ploughing it up, and sowing turnips. Instead of doing so, I top-dressed the 
whole four acres with the following substances, well-pounded and mixed to- 
gether, and this being done immediately before copious rains, the mixture was 
washed into the soil : — 12 cwt. gypsum (from TurnbuU), which, with carriage, 
cost 8s. ; 4 cwt. common salt, whicli, with carriage, cost 8s. ; — this and the 
g^'psum, 16s. Cost of top-dressing, 4s. p>er acre. 

The effect was like magic ; the plants immediately assumed a deeper green 
colour, and grew wonderfully, and this field took the lead of all my other oats, 
and when reaped the field generally was the best I had. Oats, beans, and peas 
were all particularly well filled. 1 may state further, that after the dressing it 
stood the severe drought better than any of my other crops. Wellwood is 23 
miles from the sea, and 550 feet above it. 

From other experiments which I had before made, but which I shall not fur- 
ther enter on here. I am convinced that common salt is a great auxiliary in that 
locality (if not to most others distant from the sea), and it ought to be far more 
extensively used. 

H.— EXPERIMENTS UPON BEANS. 

The following experiments were made by Mr. Alexander, of Southbar, at his 
farm of Wellwood, in Ayrshire, with the view of ascertaining the relative appa- 
rent effects of different saline top-dressings upon heans at different periods of 
their growth : — 

Experiments made at Wellwood upon a crop oi beans (1842). 

The ground was manured, previous to sowing, with 15 tons of farm-yard 
dung per Scotch acre, and the other manures applied lohen the beans roere about 
two inches high (they were sown in bi'oad-cast). The extent of ground was 2i 
acres Scots measui*e, divided into four equal proportions. 

No. 1. Dressed with f cwt. of sulphate of soda, \ cwt. of nitrate of soda. 
Result. — The effect of the di-essing was seen soon after application, by deep- 
ening the colour of the plants. The beans were deficient in straw, but remark- 
ably well podded and filled. 

No. 3. Dressed with | cwt. of sulphate of soda, 1 cwt. of gypsum. Result. 
— More straw than the foregoing, and rather better crop. 

No. 3. Dressed with J cwt. improved bones, i cwt. artificial guano, 3 bushels 
TurnbuU's humus. Result. — About the same as No. 1. 

No. 4. At first not dressed ; but, in consequence of being weakly, was afler- 
wards top-dressed with 3 cwt. of gypsum, and 1 cwt. of common salt, done in 
consequence of the highly beneficial effect produced on the four acres of mashlam 
crop above alluded to. Result. — Though done so late that the beans were already 
coming into flower, it helped them much, and they ended as well as any of the 
above. It may here be remarked, that all the beans were, particularly for that 
high district, heavy, being on trial soon after mowing 65 to 66 lbs. per bushel. 

I. Observations upon the effect of the top-dressings applied inl8il upon the crop 

of 1842. 

The following remarks are quite as interesting as any thing contained in the 
numerous experiments made this year at Barochan by Mr. Fleming's skilful 



■■ ■ n utamtami^' 



Mi 



58 EXPERIMENTS UPON MIXED CROPS. [Appet 

overseer. They are, I believe, the first systematic series of observations of the 1 
kind yet published. They are valuable, therefore, as the first steps in the line* 
oi prolonged obsei-vtitions upon the same land made during successive seasons, 
by which prolonged observations only can we hope to eliminate the eflfect of 
our variable seasons, and to arrive at true deductions in regard to the kind and 
amount of effect which this or that manure is fitted to produce. 

I do hope that Mr. Gardiner, who is capable of observing so well, and of 
experimenting so accurately, will not lose the opportunity whicli the preseat 
year will afford him of continuing these important observations: — 

, .• Top-dressings upon hay, Covenlea field (see Appendix, p. 17). On 
looking over this field at different times, and particularly early last spring, the 
square on which nitrate of soda and bones mixed had been sown was earlier 
and of a darker green colour, than any of the rest of the field, and when stocked 
with cattle, the portion top-dressed was more relished, and consequentlv always 
eaten quite bare. -i j j 

2°. Upon part of the pleasure.ground— soil a very stiff blue clay— nitrate of 
soda was sown at the rate of 160 lbs. per acre. After this application white 
clover came up very thick and strong, and it was cut three different times with 
the scythe and each time it came up stronger and thicker than the surrounding 
grass, wlnlst, before dressing, it was the weakest, and this season, 1842 it is 
better, and the portion dressed still easily distinguished. 

3°. The field at Crook's farm (see A ppendix, p. 17), which had been top. 
dressed with nitrate of soda. appUed on each alternate ridge, on beingplou'^hed up 
trom hay stubble was found tougher upon the dressed ridges, the gralk roots 
being stronger and deeper in the soil of those ridges which had been dressed. 

4 . At p. 21 of this Appendix an experiment upon moss-oats is recorded. 
Ihis was sown down with a mixture of grass and clover seeds, and cut for hay 
tms season, 1842. In examining the hay crop some of the dressings on the oats 
ot last year seemed to have had a good effect on the hay croo of this year Nos 
1 and 2 were the worst of any; No. 3 very little better, rather more clover : No! 
4 excellent, very thick of red and white clovers and rye-grass, and the hay was 
^ a good quality ; No. 5 a little better than No. 3, but fiir from being equal to 
No. 4 ; No. 6 the best of any, full of red and white clovers and rye-grass, and 
had three-fourths more hay upon it than all the others, except No. 4 • No 7 not 
better than the undressed ; Nos. 6 and 4 presented a most remarkable appearance 
compared with the others, and any person seeing them, and not knowing the 
circumsances ofthecase, would have said that these two portions only had 
been cultivated, whilst the rest had been left in a state of nalure. After bein- 
cut for hay, the aftermatli of these two portions still presented the same difference 
ot appearance m the sward, and they continue of a better colour. 

A. F. Gardiner. 

GENERAL REMARKS ON THE ABOVE EXPERIMENTS OF 1842. 

However valuable the above experiments may be, and however interesting 

belrln mind-!^ ^"""^ ""^ ^^^^ "^^^ ''P^'^^'' ^° ^^^^' '^ '^ °^ importance to 

d ^mJ^^^ ^^^^ ^^^ ^^^ ^^^"^^^ °"^^ ^^ "" ^^"^^^ season, and that a remarkably 

on?v ■ ItVl'^l- '^'SV'" ^^''*,°^ '^^^ substances employed in certain localities 
^«/T^ ,1 ^'^'^^ differing in the nature of their soil-in their distance from 
sub-eir ^''°''^' ^^^-^"'^ ^" ^^^ ^^'e'-^ge fall of rain to which they are 

«„?/ ^Y^ ^^'^ ""^^u^^^ are obtained by trials upon certain varieties of each crop 
only_, and may not be obtained even on the same spots with other varieties-of 

To^ A ' ^^^^^P^®' of potatoes, oats, wheat, or barley. 
. 4 . And that other causes, not yet noted, may have existed of sufficient in- 



No. VIII.] EXPERIMENTS UPON TURNIPS. 69 

fluence to prevent the exact results from being obtained upon a repetition of the 
experiment. 

5°. Above all, it must be borne in mind that we are yet in the first infancy of 
accurate experimental agriculture — that it will take many careful repetitions of 
our experiments before we can eliminate the effects of the seasons — of the alti- 
tude of our farms, their distance from the sea, the falls of rain to which they 
are subject, and the kind of soil of which they consist. In the mean time our 
most careful deductions must be considered as partial only, and as open to doubt 
—as facts by the combination and compaiison of which we are hereafter to ar- 
rive at more general truths. 

With these preliminary observations, I turn to the experiments themselves — 

A. — T/ie experiments upon turnips. 

The first series, those of Lord Blantyre — except the general answer that saline 
substances cannot replace fann-yard raanure — afford no very satisfactory results. 
They exhibit, indeed, some striking circumstances — such as 

1°. That 100 lbs. of salt per acre may, in a diy season, reduce the natural or 
unaided produce of turnips one-half— and that thesome weight of nitrate of soda 
may reduce it one-fourth. 

2'^, That in such a season as much as 16 cwt. of rape-dust per acre may be 
applied, one-half drilled in, and one-half as a.io'^-dvQSsiYig, without producing any 
sensible benefit. 

o°. That the same may be the case, if eight cwt. of rape-dust be drilled in, 
and half a cwt. of nitrate of soda be afterwards applied as a top-dressing — 
while if the same weight of common salt Joe used as a top-dressing instead, 
the crop will be increased one-half 

These results are too anomalous to be considered for the present as more than 
accidental. They may possibly be explained either by the different degrees of 
moisture of the several parts of the field in which the mixtures were applied — 
or on the supposition, which is very probable, that in the concentrated state 
some of these saline substances are more hurtful to the growing plant than others. 
It is to be regretted that the season was so unpropitious to this series of experi- 
ments, for though the following experiments of Mr. Fleming afford some valuable 
information, further knowledge still is wanted in regard to the relative effects of 
different saline substances upon the groivth of turnips, where no fermentible ma- 
nure is applied, 

4°. In these experiments, a striking contrast is pi-esented between the effects 
of rape-dust and those of guano. 16 cwt. per acre of the former gave only 3 J 
tons of turnip bulbs, while 2 cwt. per acre of the latter gave 5 tons. It appears, 
therefore, that rape-d^ist requires moist weather or occasional rain, while guano, 
even in very dry seasons, will produce a considerable effect. This is consistent with 
what we know of the employment of the latter substance as a manure on the 
arid plains of Peru. 



II. The next four series of experiments, those of Mr. Fleming, are rich in re- 
sults and suggestions, 

1°, Limits of error. — The first observation which a careful examination of 
them will lead the reader to make — and it appears to me to be a very important 
one in reference to all future experiments of this kind — is suggested by the se- 
cond series — those upon early ycllo^o turnips, p. 44, 

In this series there are included two plots (Nos. 5 and 18), upon which no 
manure was used. Upon one of these the produce amounted to 12 tons 17 cwt., 
upon the other to 11 tons 8 cwt. only — being a difference of 1^ tons, or one- 
eighth of the whole. This difference between two equal portions of the same 
field, apparently similar in soil, could scarcely, I think, have been anticipated, 
and it shews that — where the produce obtained by the application of t/wo unlike 
manures, to this turnip crop, does not differ voore than IJ ions per acre, the effects 



%. 



^^ EXPERIMENTS UPON TURNIPS. [Appendix, 

of ^ two majiures may be considered as pradicallv eqnal-sinct \hh amount nf 
d^ffei^nce may have arisen from the unlike qualifies of the two Sots^S L 
wliich tlie manures were respectively applied ^ ^''"'^' '*" 

r^ot r. '!i''" i^^P^'t^nt practical rule for enablin- us to judffe accuratelv in 

be^S3LV to fore t ZTl' "'"""' """'^ ''% enlertained. I. appeaJ?"o 
tions are inte^difwl h!'^ fuure experiments from which accurate deduc- 

land in several diffp,-.,,?! of weighings of the produce of equal portions of 

tilled and Sir'e'd " eCrL'v' TM *''"■,.";? ''"""' "^ '''"°' '>- I'-" 
isfactory light upon the amo?,n,„/' ^ ■ "T-''', ''V°'' '=""'« "=""»'" ""^ ^«- 
take Blace in thHL,. "^ variation which, from natural causes, niav 

undeJ' hp ,!,« "°P' S"*" "P»n different parts of the same field and 

i£Lt' :cZZ":::!::':,jl: ^''T'r f ™='"^" •» «"-^'- 'he 

with the xn««r1,e,t.L " ' I? " ""^ '''''*"''^ °f ^i":!' experiments as are made 

*."4*r» B,]T'"° "'?.'™ "i"™ "'■"«= different manures we apX' 

dete tb ^ap "ie~of mateSvlt^'^'^^^ '" "f ^°^' ^'''"<='' "'" ">" -""« 

of the two ormorf Plots we ihn'd °" "■'"" ""J '".'',''<^- Tl--^ ">■=»" P™'i'"=e 

those to whrchTdress?nJhastLn'''°™Pr''.'''''' '^'^ "''»" P™*'^'' of 
a?e effecf of ,1,. ,1^. ^ u ' . S'"*". W'H indicate more nearly the aver- 

^Thfreade win nerceir-'''';K ^"" "7'"^' "P°" *^ S'^™ ^°« and'^crop 

b^hVpi^cttr^'rurur^r s^^^^^^^^ »<'-■ ^ --p^' fain^rrs^'o™ 

I :«; „°f fua^ :Jr ^7 ^ '™' « '«■ °f *^*» • • (P- 44). 

20 bushels of wood-ashes J 32 tons 2 cwt. of Early Yellow (p 44) 

5 cwt. of guano alone 32 tons 15 cwt. of White Globes . (n 46) 

It IS no small matter of congratulation, that this important reduction has been 



No. VIll.] EXPERIMENTS UPON TURNIPS. 61 

mainly brought about by the expression of scientific opinion, and by the readi- 
ness with which various persons, manure-manufacturers and others, have put 
in practice the suggestions contained in the preceding part of this Appendix 
(p. 26), for the formation of an artificial mixture in imitation of the natural 
guano. The fear of competition produced its natural effect upon the market, 
and led the importers of this substance to content themselves with a smaller 
profit. It is to be hoped that the more extended sale which has followed the 
reduction, will leave the spirited merchants who first brought it into the countiy 
no reason to regret the diminution in price. The benefits which the practical 
agriculturist derives from one such reduction as this are not all at first 
sight perceptible. The demand for guano has so greatly lessened the call for 
rape-dust, that it has also fallen in price from £S to £5 10s. per ton. Thus 
ramified and extended are the results of a single chemical investigation — or the 
publication of a single well-founded scientific opinion. 

3°. Artificial Guano. — In connection with this subject it is important to as- 
certain to what extent the attempts to manufacture a substitute for the natural 
guano have been attended with success — in so far as the turnip crop is concern- 
ed. The only comparative results which the above experiments present, are the 
following — those upon Swedes being obtained by the use of 3 cwt. of each 
mixture, those upon the yellow and white turnips by the use of 5 cwt. of each: — 

Swedes. Early Yellow. Whife Globe. 

1°. Nothing . . . 12 tons 5 cwt. 12 tons 17 cwt. — tons — cwt. 

2°. Natural guano . . 23 " 8 " 32 " 2 *' 32 " 15 " 
3°. Barochan artificial guano 17 "14 " 24 '' 2 " 22 '« 10 " 
4°. Turnbull's artificial guano 14 " 11 " 21 " 4 " _ " _ «« 

These results show that, when equal quantities are employed, equal results 
are not obtained from the natural guuno and from the artificial mixtures. 
It also appears that Mr. Fleming's mixture is much more eflicacious than that 
of Mr. Turnbull. They are made up, with some modifications, after the recipe 
given in the preceding part of this Appendix (p. 25), but are, no doubt, suscep- 
tible of improvement. It is, indeed, one of the indirect benefits which will re- 
sult from the introduction of this foreign manure, that it will stimulate to expe- 
riments, by which we shall, no doubt, at last successfully imitate it — and will 
lead, at the same time, to a more general and thorough understanding of the 
principles upon which mixed manures ought to be compounded, and of the 
mode of preparing them with the greatest possible economy. Many crude mix- 
tures may be made at first, by dealers in manure and others, and many instan- 
ces of want of success may occur, but now that we have adopted the system of 
recording results, whether apparently successful or the contrary, there is Utile fear 
of our arriving at scttisfactory and economical truths at last. 

Suggestion III. — In experiments made for the pui-pose of aiding the real ad- 
vance of scientific agriculture, I would suggest that no mixture should be used- of 
which the composition is not'exactly knoion — which, therefore, has not been either 
made by the experimenter himself or by some dealer upon whose honor perfect 
reliance is to be placed. The use of the random mixtures now sold under so 
many different names, however successful they may be in this or that case, can 
never lead to the discovery of viseful agricultural principles, and, therefore, are 
unworthy of the attention of the cultivator of inductive experimental agriculture. 

4°. Sulphate of ammonia. — These remarks lead me to notice the effect ascrib- 
ed in Mr. Fleming's second table (p. 44), to sulphate of ammonia — one cwt. 
of which nearly doubled the crop. Thus — 

The unmanured soil gave . . 12 tons 17 cwt. 
With 1 cwt. of sulphate of ammonia 24 " 11 " 

This is exactly equal to the effect produced by 15 cwt. of rape-dust at a cost of 
je6 lOs. But the sulphate of ammonia here employed was that prepared by 
the Messrs. Turnbull, of Glasgow — which is not merely sulphate of ammonia, 
but a varioM-c and undetermined mixture. It is prepared from urine, and I be- 



62 EXPERIMENTS UPON TURNIPS. [Appe7ldix, 

lieye is contaminated also witli a considerable proportion of saline substances 
artificially added to it That it contains many substances useful to plants there 
can be no doubt, and that it may prove a valuable manure is exceedingly pro- 
bn.ble, but wider its present lutme it can only lead to false deductions in expe- 
rt '\ental agriculture — and the use of it, therefore, in comparative trials such as 
th. 33 we are now discussing, ought to be avoided. It is only, as I have already 
said, from the use of pure substances mixed in known proportions, that valuar 
ble, iDecause undoubted, conclusions can be drawn. It is in vain to attempt to 
eliminate the effects of diversity of soil and climate, if new causes of diversity 
are introduced by the very substances with which our experiments are made. 

5°. Bones dissolved in muriatic acid. — The action of bones is not in general 
exhausted in a single season. If they are in the state of fine dust, they decom- 
pose more quickly and cease to act in a shorter space of time. By dividing 
theiii still more minutely, or by solution in an acid, it has been thought that 
their apparent efficacy might be increased. Mr. Fleming, in 1841, made some 
experiments which seemed to justify this conclusion. In the present tables 
other results are exliibited, which favour the same opinion. I place togeUier 
here the results upon potatoes, as well as upon turnips, for the purpose of 
comparison : — 

Bone-dust. Bones in muriatic add. 

16CWT. 18 CWT. 3 CWT. 10 CWT. 

tons. cwt. tons. cwt. tons. cwt. tons. cwt. 
Swede Turnips . . . 14 17 — — — — 18 11 

White Don Potatoes . . _ _ 9 15 12 15 — — 

These results, the only ones contained in our tables which can be compared 
together, are both greatly in favour of the dissolved bones, in so far as the action 
upon the first crop is concerned. It will require longer observation to deter- 
mine in which form the same weiglit of bones will produce the more lasting 
effects — and will be the more economical on the whole. 

6°. Nitrate of soda. — The effect of 1 cwt. of this salt per acre upon the early 
vellow turnip is very remarkable (p. 44), having given upwards of 27 tons of 
bulbs, at a cost of 25s. It is to be regretted that no similar experiment is re- 
corded upon the other varieties of turnip, either by Mr. Fleming or by Mr. Al- 
exander. In the text (Lecture XV., p. 335 to p. 342) an abstract of all the pub- 
lished results hitherto obtained by the use of nitrate of soda will be found in a 
tabulated form. 

7°. Lime. — A.n interesting result in Mr. Fleming's first table may hereafter 
lead to some satisfactory experimental determinations of the points considered 
still doubtful in regard to the form in which, and the time when, lime may 
be most efficaciously applied, in reference to the culture of particular crops. He 
caused carbonate of lime and caustic (newly slaked 1) lime to be sown in the 
drills without manure, and the effect upon the crop of Swedes was as follows : 

Soil unmanured 12 tons 5 cwt. 

Carbonate of lime, 20 bushels . . 16 " 11 " 

Caustic lime, 50 bush els . . 11 " 8 " 

The immediate effects of lime applied in these two forms was very different — 
the caustic lime lessened the turnip crop, while the carbonate increased it by 
4^ tons. This effect most probably arose from the lime, in its caustic state, 
taking from the soil the carbonic and other organic acids from which tlie roots 
in the early infancy of the plant would have dex-ived a portion of their nourish- 
ment, and thus i-etarding and stunting theii- growth. At all events the experi- 
ment seems to indicate that lime ought to be in the state of carbonate — the mild 
state — more or less entirely, if it is intended to benefit the crop to which it is 
immediately applied. When mixed with manure, however, where vegetable 
matter abounds in the soil, or where the lime is merely harrowed into the sur- 
face—in all which cashes it will readily become, in a great measure, saturated 
with carbonic acid — the skilful farmer will understand that the deduction drawn 
from the preceding experiment will not apply. 



No. VIII.] EXPERIMENTS UPON TURNIPS. 63 

8°. Rapc-dust. — -The results exhibited in this yeai-'s experiments, generally, 
are not so favourable to the employment of this substance as was to be expect- 
ed. The reason, however, is, probably, that which has already been suggested 
in discussing the results obtained at Lennox Love — that rape-diist requires a 
moist soil or occasional showers. But this itself is an important probable deduction. 
The reader will find a comparative view of the whole of the results with this 
substance in the text (see Lecture XVII.) 

9°. Animal Charcoal. — The effect of animal charcoal upon Swedes in Mr. 
Fleming's experiments is only inferior to that of guano. It is certainly deserv- 
ing of further trials, and especially in comparison with what is called exhausted 
animal charcoal — that which has already been used in the refining of sugar. 
In France, the latter is said to be prefen-ed to the former, and to be sold by the 
sugar refiners at a higher price than they pay for it in the recently prepared 
state. . 

10*^. Other mixed manures. — In regard to other mixed manures, the reader 
will find much practical information by the study especially of No. 3 of Mr. 
Fleming's tables, p. 45 ; and of Nos. 1 and 2 of those of Mr. Alexander, p. 46. 
These are the more worthy of the attention of the practical man, since Mr. Flem- 
ing considers himself justified in remarking as the general result of the experi- 
ments in ]D. 45, that any of the mixlurcs used loill in his lo.nd produce an ave- 
rage crop of turnips at a kss expense than farm-yard manure. This is the kind 
of I'esult which it ought to be the ambition of every practical man to work out 
for himself upon his own land. 

11°. 9izQ and weight of bulbs. — There remains only one other topic in con- 
nection with these experiments to which space will permit me at present to ad- 
vert. In the remarks upon the table inserted in p. 44, it is stated that the tur- 
nips on the plots dressed with — 

Guano and wood-ashes — loere pre-eminent for size of bxQhs. 

Sulphate of ammonia — large in bulb, but soft, and light in weight. 

Potash and lime, salt and lime, sulphate of magnesia, nitrate of soda-*-5maZZ 
ill bulb, but firm and solid. 

Bone-dust and the artificial guanos — both containing bones — the bulbs firm 
and solid, but not remarkable in size. 

Now upon the solidity of the bulb — other things being equal — it may be pre- 
sumed that the relative nourishing properties of different species of turnip will 
materially depend. The quantity of water which different specaneiis of the 
same variety of turnip contain varies from 79 to 91 per cent. — that is, some tur- 
nips of the same specit^s coiitain only four-fifths, while others contain upwards of 
nine-tenths of their loeight of water. In other words, tlie same variety of turnip 
may contain such unlike quantities of water, that 2 tons grown on one spot 
may not contain more than 1 ton grown in another. The %Deight of bulbs, there- 
fore, is no safe criterion of the quantity of food raised on different parts of the 
same field — where the general treatment, or the substances applied to aid the 
growth, have been different. 

Now in the above experiments the guano gave 32 tons of very large, the sul- 

Eihate of ammonia 24 of soft, and the nitrate of soda 21 of small and solid bulbs, 
t is probable, therefore, that the actual quantity of food raised by the aid of the 
niU'ate of soda was much greater than even by the natural guano. It may also 
have been that the 14^ tons of solid bulbs given by the sulphate of magnesia, 
or the I2i raised from the land without manure at all, may have contained as 
much nutriment as the 24 tons of soft bulbs raised by the sulphate of ammonia. 
Suggestion IV. — The bare possibility of such a circumstance as the last, 
shows how little absolute confidence we can place in the numerical results as 
yet obtained, considered as evidences of the greater or less amount of food, which 
the use of this or that kind of manure will enable us to raise from a given ex- 
tent of land. It suggests, also, the necessity of a further determination of the 
relative quantity of water contained in our experimental turnip crops. Tliis 
will, without difficulty, be effected by selecting three or four turnips of different 



Red Don. 
6 tons 15 cwt. 

a a 


Connaught Cups. 
5 tons 15 cwt 

U 11 


14 " 6 " 

10 ''■ " 


13 " 14 " 
13 " " 



g4 EXPERIMENTS UPON POTATOES. {AppendiXi 

sizes from each sample — cutting a slice from either side, and one from the mid- 
dle of each turnip — weighing the whole— drying them then, first in the air, 
aflerwords before a gentle fire, and lastly in an oven so hot as not to brown white 
paper or dry flour, and then weighing. The loss being the weight of the water 
11! the turnips, will enable the experimenter to determine the relative quantities 
oj food raised upon his different plots, and therefore the relative value of his 
dilFerent applications or methods of culture. 

In this suggestion the reader will perceive another of those precautions which 
the prosecution of our experimental inquiries renders necessary — future years 
will suggest otliers — but the increase of trouble will not deter the zealous la- 
bourer in this important field — for the more precautions and difficulties multiply, 
the greater the honour will be to those who by perseverance shall successfully 
overcome them. 

B . — The Experiments upon Potatoes. 

Nearly all the experiments in the first table of results (p. 48) were made witli 
mixed manures. 

1°- Chjiam and rape-dust. — Among these the effect of guano is again striking, 
and upon two of the varieties greatly exceeds that of rape-dust. Thus, the pro- 
duce of the three varieties tried was — 

White Don. 
Unaided soil . . . 1 tons 1 cwt. 
With 3 cwt. guano. . 18 " 9 " 
With 4 cwt. guano . .— " — " 
With 1 ton of rape-dust . 13 " 6 " 

We are not enabled, by the experiments before us, to compare its effect with 
that of farm-yard manure. 

A curious question suggests itself upon the inspection of the above numbers 
— one which could scarcely have arisen in our minds, had not differences such 
as the above presented themselves among the results of our experiments. 
Nothing is more common than to ask which of several varieties of potato is the 
more prolific — and a practical man who has made the trial has no difficulty in 
giving an immediate answer to the question. But the experiments of Mr. Flem- 
mg seem to say that the relative wei<:ht of crop yielded by each of two or more va~ 
rieties of potato, depends upon the way in ichich you treat or manure them. With 
one treatment a variety (A), with another a variety (B), will give the heaviest 
crop. Thus, our three varieties gave with — 

White Don. Red Don. Connaught Cups. 

Natural guano . 18 tons 9 cwt. 14 tons 6 cwt. 13 tons 14 cwt. 

Rape-dust . . 12 " 6 " 10 " " 13 " '« 

Both substances agree in saying that the white is considerably more prolific 
than the red Don. But while the guano adds that both Dons are more prolific 
than the Cups, the rape-dust pronounces the latter variety to be superior to either 
of the former. Now it may have happened that in the last case of the three, the 
rape-dust, from some circumstance not noticed, may have acted better than in 
tlie other two cases, and that in this way the discordance may have arisen. Un- 
fortimately, however, there are upon record no other experiments made upon 
any two of the varieties of potato with other substances used in like proportion 
— by which this question might have been in some measure solved. But the 
interesting, and as it may hereafter prove, imponant inquiry suggests itself — 
what is the order of relative productiveness of the several varieties of the same culti- 
vated plant ^ xoheii they are severally dressed or manured with this or with that sub- 
stance? This question will, no doubt, hereafter lead to extended series of very 
refined experimental inquiries, from which not only much knowledge but much 
practical benefit may be derived. 

Suggestion V. — It may be, for instance, that a given variety of potato, turnip, 
oat, liarley, &c., is more valuable as food, more agreeable to the taste, or brings 



I 



ii)mA. 'r^-T'-^i'-'^nf-- inir'^yKf^'-^-r- 



No. VIIL] ' EXPERIMENTS UPON POTATOES. , 65 

a better price in the market — but by the ordinary modes of culture is the least 
productive of those genex-al]y cultivated. It w^ould then be not only an interest- 
mg, but an important economical question to ask — could this variety be render- 
ed more productive by a diiFerent mode of treatment — one especially adapted to 
its own nature ? Would the practical man not rejoice to think that such a result 
could be brought about by the aid and suggestions of science % Yet this is tlae 
result to which the refined series of experiments suggested by the question 
above proposed may possibly lead. 

May I venture to hope that some of my more zealous readers will be induced, 
during the present or succeeding summer, to make trials of the relative effects 
of the same saline or other known substances and mixtures, upon different varie- 
ties of the same crop — of potatoes, turnips, wheat, (Sec, in circumstances other- 
wise equal, in some such form as the following : 

Variety A. Variety B. Variety C. Variety D. Variety E. 

Substances. Substances. Substances. Substances. Substances. 

A. I B. I C. A. 1 B. I C. A, I B, I C. A. | B. | C. A. | B. | C. 

The results if carefully ascertained axe sure to lead to good, if they should 
not be successful at once in solving tlie problem above proposed. 

3°. Solidity and size of the potatoes. — Nothing is said in the observation of 
Mr. Fleming, or his overseer, in regard to the size or solidity of the different 
varieties of potato, or of the different samples of the same variety on which the 
experiments were made. Yet in connection with the remarks 1 have already 
offered upon these qualities of the turnip, it is proper to add that the potato is 
subject to similar variations in the proportion of water it contains — and, there- 
fore, in the relative amount of nourishment capable of being afforded by equal 
weights of its different varieties. 

Some potatoes contain less than 70, others upwards of 80 per cent, of water, 
so that while 100 tons of one sample will give only 20 tons of nourishment, the 
same weight of another will give 30 tons, or one half more. In general, such 
as grow on heavy or clay soils, or such as are less ripe, contain the most, while 
those which have been planted upon sandy spots, or are fully ripe, contain the 
least water. But the effect produced by different soils we begin now to 
see may be produced by different methods of dressing or medicating our crops 
also. 

Suggestion VJ. — It would be interesting to determine, therefore, by actual 
experiment, the relative proportions of water contained in the produce of the 
several experimental patches of potato ground upon the same field, when 
equally ripe, or when dug up on the same day. This would afford us the 
means of approximating still more closely to the true economical action of our 
different manures upon the potato crop. It may turn out that in certain cases 
the increase of produce, as indicated by a greater weight, is only apparent, 
while the increased amount of food raised may in other cases be considerable, 
though the balance indicates no increase of weight. 

Did we know the relative proportions of water in the several samples of the 
three varieties of potato raised by Mr. Fleming by the aid of guano, and of 
rape-dust, ah'eady compared together, our conclusion in regard to their relative 
productiveness, when treated by either substance, might be materially altered. 
I hope, thei-efore, that this point also will hereafter arrest the attention of some 
of our experimentalists. 

4°. Permanent effects of saline mamires on the future productiveness of the 
seed. — Recommending to my practical readers a careful consideration of the 
effects^pf an admixture of wood-ashes with the several dressings applied to the 
turnip and potato crop, I pass on to the two following series of experiments 
with saline manures upon the potato crop, as given on p. 49. These two series 
are well conceived, and the results very instructive. Of these results the one 
which seems to me most deserving of the attention of the practical man is con- 



66 EXPERIMENTS UPON POTATOES. , [Appendix, 

tained in a few words, thrast in as it were, among tlie remarks appended to the 
table (1°, p. 49.) In the later printed copies I have caused them to be put in 
itcdica, witn the view of bringing them into notice. If the reader will turn to p. 
20 of this Appendix, he will find a remarkable experiment recorded, in which, 
by top-di-essing well-manured potatoes, with a mixture of ^ of nitrate and § of 
sulphate of soda, the enormous crop of 30 tons an acre was obtained from the 
small plot experimented upon. Some of these potatoes were kept for seed, and 
planted alongside of others of the same variety, which had not been so dressed, 
ar>d the result is stated in the few words above i-eferi'ed to — " These last, v,nder 
the same treatvient in every respect^ did iwt prodiice so good a crop by 15 bolls (3| 
ions') per acfer 

In so far, therefore, as tliis experiment is to be relied upon — for we must not 
be hasty in drawing general conclusions — it appears that the benefit to be de- 
rived from a skilful treatment of the potato plant does not terminate with the 
greater immediate crop we reap, but extends also into future years, improving 
the seed and rendering its after-culture more productive. 

Suggestion VII. — This idea is worth pursuing, were it only for the purpose 
of making out the possible existence of so important a physiological law — how 
much more when it appears so pregnant with important practical results. But 
thus it is in all cases, that the prosecution of experimental research, with im- 
mediate reference either to purely scientific or to pui'ely practical results, ends 
in improving and benefitting both abstract science and economical practice. 

I am unwilling to follow out or to reason upon this possible law, as if it 
were really established ; but the possibility of its tmth appears to throw light 
upon such questions as this — why the seed must occasionally be changed if 
large crops are to be continually reaped. One soil may be adapted to give the 
plant a large supply of this or that substance in which the other soil is com- 
paratively deficient ; and it may be possible to medicate our seed-corn, while 
growing, so as to give it the qualities which at present it can acquire only by a 
change of soil. 

All this, however, can be only determined by experiment, and the intelligent 
reader will net fail to be stmck with the remarkable richness of these first trials, 
in suggestions for future carefully conducted experimental researches. 

5°. How should saline manures he applied to the potato crop? — Ought they to 
be mixed with the manure, or to be applied as a top-dressing 1 JMr. Fleming's 
experiments do DOt fully solve this question ; because the soil on his two fields 
was very unlike in quality. Thus with manure alone the one field produced 
12 tons 15 cwt., the other only 8 tons 17 cwt per acre. A perfectly satisfactory 
solution of the question can be obtained only by experiments with the same sub- 
stances, upon the same soil, and with the same variety of potato. Yet the experi- 
ments now before us add considerably to our knowledge upon tliis point, and 
such of them as are capable of being compared together are much in favour 
of mixing tJce soline substances loith the manure. Thus applied in nearly 
equal proportions by both methods, nitrate of soda, sulphate of magnesia, and 
sulphate of ammonia, gave the following results : — 

FIRST FIELD. SECOND FIELD. 

Top-dressed. Mixed with manure, 
tons. cwt. tons. cwt. 

Manure alone 12 

Nitrate of soda 1(5 

Sulphate of magnesia .... 13 

Sulphate of ammonia .... 14 
The proportionate increase, therefore, in these three cases, is greatly in favour 
of mixing with the manure, but something may depend upon the soil and 
season ; and, therefore, other experiments are necessary before we can draw a 
general conclusion. It may prove that some act better when applied in the one 
way, and some in the other. 

C>°. S^dphaicof soda. — With this substance applied in either way, the singu- 



15 


8 


17 





12 


7 


5 


11 


7 


10 


13 


7 



No. VIII] EXPERIMENTS UPON POTATOES, BARLEY AND OATS. 67 

lar and consistent result was obtained that 2 cwt. per acre caused no alteration 
whatever in the weight of the produce upon either of the two on which the trials 
were made. Of the respective qualities of the crops nothing is stated. 

7^. Sulp-Jtale loith nitrate of soda. — The above result with sulphate of soda 
alone, is the more remarkable from the known effect produced by this and other 
sulphates when mixed with niti-ate of soda. This year, also, the mixture of 
nitrate with sulphate of soda added one-half (G tons per acre) to the crop, a 
greater proportionate increase even tlian in the experiment of 1841, which gave 
an increase of 8 tons out of a total produce of 30 tons per acre. But this 
season Mr. Fleming has tried, with still greater success, a rnixtiire of 1 cwt. 
each of sulphate of magnesia and nitrate of soda, the produce rising by the use 
of this top-dressing to 22^- tons. The relative effects of the two sulphates 
would have been more clearly proved, had the proportions of nitrate of soda 
applied per acre in the two mixtures been the same. 

8^. Nitrates of soda and potash. — Another interesting fact to add to those 
alrerdy registered upon the relative efficiency of these two saline substances, is 
presented in page 49. One hundred weight and a half of — 

Nitrate of soda gave . , 16 tons. 

Nitrate of potash gave 18^ tons. 

This difference may have been due to accidental causes — or the I8i tons of 
the one result may have contained no more food than the 16 tons of the other; 
but the multiplication of accurate experiments will eventually lead us to the 
truth. Apparent failures and discordant results must not discourage the prac- 
tical man. By recording all trust-worthy I'esults, the light will almost sponta- 
neously spring up at last. 

9"^. Silicate of potash. — The results obtained by the use of this substance, and 
the remarks appended to them (p. 50), are deserving of much attention. In re- 
ference to this compound, and to the silicate of soda, I beg the reader to turn to 
the suggestions contained in this Appendix, p. 40. 

10°, Mixed ma7iures. — The mixtures in page 50 will no doubt be imitated, 
and by those who can obtain them o? known composition, comparative experi- 
ments may be tried with advantage both to theory and to practice. 

C . — The Experiments upon Barley. 

The true practical value of the experiments upon barley will be shown by 
placing them in the following form : — 

Increase. £ a. d Cost per bush. 

Nitrate of soda with common salt, gave 5 bush, for 17 6 — 3s. 8d. 

Sulphate of soda with sulphate of magnesia, 7* bush, for 15 6 — 2s. Id. 
Guano (at 25s.), . ... 17" bush, for 3 18 — 4s, 7d. 

Common salt, ..... 6 bush, for 46 — Os, 9d. 

Turnbull's artificial guano, . . 2 bush, for 1 4 — 12s. Od. 

The cheapest application, without doubt, upon this soil, is common salt. 
At half the above price guano would produce the barley at 2s, 3d. per bushel, 
and the larger quantity reaped, together with the value of the straw in the pre- 
paration of manure, may satisfy many that either guano or the mixture of sul- 
phates may be used with profit. It is a further recommendation of the common 
salt, however, that it produced the heaviest, while guano produced the lightest 
grain. 

From the experiment with nitrate of potash no result can fairly be drawn, in 
consequence of the great drought of the season (see Mr. Gardiner's remarks). 

D. — The Experiments vpon Oats. 
1°, Negative effect of saline manures. — The first of the two series of experi- 
ments above recorded being made at Lennox Love — like those made at the same 
place upon turnips — derive their principal interest from the illustration they 
afford of the negative effect of saline manures upon the otu crop, under the in- 



(38 EXPERIMENTS UPON OATS AND WHEAT. [Appendix^ 

fluence of great heat and drought. I select the more simple and striking cases 
of diminution. The undressed part of the field produced 54 bushels per acre. 
Common salt diminished this produce by 6 bushels. 

Nitrate of soda 12^ " 

Sulphate of soda 15| '* 

Rape-dust 9 " 

Soot . m " . 

while 2 cwt. of guano raised the produce to 70 bushels, being an increase of 16 
bushels. 

Tliese results not only confirm the deductions which we have already drawn 
from the preceding experiments upon potatoes and turnips — that guano will act 
even in our driest seasons, while rape-dust requires at least occasional rain — but 
they go further in showing that, like the saline subsisnices, rape-dust^ and even soot, 
mil materially diminish the oat crop, if tlie season be distinguished by remarkable 
drought. 

2°. Moss oats. — The experiments upon moss oats (p. 53) are a continuation 
and extension of those of 1841 with gi-eater attention to accuracy in the determi- 
nation of the produce. The last column in the table speaks for itself The 
general produce of the field being 43 bushels per acre. 

Increase. 
Sulphate of ammonia gave ... 9 bushels 

Sulphate of soda with nitrate of soda gave 18 bushels 

Bones in muriatic acid gave ... 18 bushels 
Silicate of potash, mixed with the above, gave 22 bushels 
In the last two cases the straw, which is usually imperfect in oats grown upon 
moss land, was strong and healthy. It is obvious, therefore, that all these exper- 
iments deserve repetition, though, as here set forth, the increase of grain by Nos. 
2 and 3 was obtained at the least cost, and, therefore, to the economist will ap- 
pear most important. 

E. — The Experiments wpon Wheat. 
I. Effect of drought. — The first series, those made at Lennox Love, aiford in- 
teresting illustrations of the effect of great drought in modifying the action of sa- 
line manures and of rape dust, upon the wheat crop. The more prominent 
results ai'c distinctly brought out when thrown into the following form. The 
produce of the undressed part of the field being 47^ bushels an acre, this produce 
was affected by the several substances employed in the following manner : — 

Decrease per acre. Increase per acre. 
Common salt, 1 cwt 1^ bush. — 



Cost per bush 


2s. 


3d. 


Is. 


7d. 


Is, 


6d, 


2s. 


Od. 



Sulphate of soda, 1 cwt. 
Soot, 32 bush. . 
Nitrate of soda, I cwt. 
Rape-dust, 16 cwt. 
Guano, 2 cwt. 



9^ bush. — 

slight. — 

— slight. 

— 3^ bush. 

— \ bush. 

Thus, the nitrate of soda and the soot did no harm, though the di-ought did 
not pemiit them to do any good. Common salt shghtly, and sulphate of soda 
largely diminished the crop ofgrain— while of these four substances the sulphate 
was the only one which diminished the yield ofsti-aw. Nitrate of soda and 
soot largely increased it. 

On the other hand, guano slightly increased the yield ofgrain, and rape-dust 
added 3i bushels to the natural produce, both also augmenting the weight of 
the straw by about one-tenth of the whole. 

In this case, then, the rape-d\^t surpassed in beneficial eflfect the natureJ 
guano, though, as we have already seen, it proved greatly inferior to the latter 
when applied in similar proportions to oats, potatoes, and turnips. 

2°. Suggestion VIII. — This fact suggests an interesting inquiry. It is known 
that one "of the most lucrative modes in which rape-dust has been hitherto 



No. VIII.] EXPERIMENTS UPON OATS AND WHEAT, 69 

employed as a manure has beea in top-dressing the wheat crop (see the prece- 
ding part of this Appendix, p. 19). Has it,therefore, some special adeiptaiion to 
the wheat crop — which will account at once for its comparative failure upon oats, 
turnips, and potatoes, and for its superior efficacy to guano upon the wheat crop 
— in the proportions stated, and even in a very dry summer 1 The comparative 
efficacy of the two substances applied in various proportions is certainly deserv- 
ing of furtlier investigation. It will be a gain not only to practical but to theo- 
retical agriculture, should it be established that rape-dust can be profitably 
applied to the wheat crop, in circumstances when it would be thrown away upon 
oats or turnips. By turning to the next series, that of Mr. Fleming (p. 54), it 
will be seen that the last result there stated is also favourable to the action of 
rape-dust upon the wheat crop.* 

3°. Mutually counteracting iniflucTice of different vmnures. — But another curi- 
ous observation presents itself in the table of Lord Blantyre's results. It is in 
the apparent struggle between the good and evil influences of the rape-dust on 
the one hand, and of the saline substances on the other, when they were applied 
together to the same plot of wheat (see Appendix, p. 19). Thus, when applied 
in the proportions above stated — 

Increase. Decrease. 

Common salt gave .... — IJ bush. 

Rape-dust gave 3| bush. — 

One-half of each gave . . . 2§ bush. — 

Or the natural effect of the rape-dust was lessened one-third when mixed vnth 
the given iveight of common salt. So, also — 

Increase. Decrease. 

Sulphate of soda gave ... — 9? bush. 

Rape-dust gave ..... 3^ bush. — 

One-half of each gave ... — 3 bush. 

Or the influence of 1 cwt. of sulphate of soda for evil was one-third greater than 
that of 16 ciot. of rape-dust for good — in the given circumstances of soil, climate, 
and crop. This result, which at present seems only curious, may hereafter lead 
to the establishment of interesting truths capable of practical application. 

Suppose, for instance, that upon two fields rape-dust were applied to the 
wheat crop at the rate of 16 cwt. per acre, and that the one field contained na- 
turally in its surface soil the pi'oportion of sulphate of soda employed in Lord 
Blantyre's experiment, while the other contained none — then in the one case 
the rape-dust would not only expend all its influence in overcoming the tenden- 
cy of the sulphate to lessen the crop, — but would even seem to do harm if the 
produce were compared with that of another field, of apparently similar soil, 
near the surface of which this abundance of sulphate did not exist ; while, in the 
other case, the rape-dust, having no counteracting influence to overcome, would 
spend itself entirely in increasing thegrowth of the plant and the final yield of 
grain. 

Or suppose an artificial guano or other mixed manure artificially prepared, 
to contain two or more substances which, in the soil they are applied to, have 
a tendency to produce opposite effects — the one to increase, the other to 
diminish, the amount of produce — the effect of this conflicting action of its 
component substances would be such as to render the mixture of less efficacy, 
perhaps of no efficacy at all — it might be even injurious to the crops, — although 
it contained substances which, if applied alone, would have exhibited a power- 
ful fertilizing action. 

These two illustrations are sufficient to show the Icind of light which obser- 
vations, such as the one above adverted to, may hereafter throw upon practical 
agriculture. 

II. The substance of Mr. Fleming's table (p. 54), may be thus presented. 

' See also the subsequent observations on the experiments upon beans. 



70 EXPERIMENTS UPON WHEAT. [Appendix, 

The unaided produce of the soil was 25 bushels an acre, and the efF:ct of the 
dressings as follows : — 

Increase. Decrease. 

Guano, 3 cwt 6 bush. — 

Rape-dust, 5 cwt., sulphate of magnesia, | cwt. . 3^ bush. — 

Sulphate of soda, 1| cwt., nitrate of soda, | cwt. 1| bush. 

Common salt, 3 cwt — 3h bush. 

Common salt, 3 cwt., dissolved bones, 1 cwt. . — 2 bush. 

TurnbuU's artificial guano produced no sensible effect. 

Under the circumstances, besides being favourable to guano, the above re- 
sult is also in favour of the mixed sulphate and nitrate of soda, which we have 
seen to operate beneficially upon so many other cultivated plants. The entire 
crop appears to have been injured, not only by the summer's drought, but by 
the severity of tlie preceding winter. 

In regard to common salt, it is worthy of remark, that the grain dressed by 
it, whether oats, barley, or wheat, in Mr. Fleming's experiments of this year, 
has been always heavier per bushel than any of the other samples tried. This 
accords with the previous results of some other experimenters; but it does not 
agree v/ith Mr. Fleming's observations upon the wheat of 1841, nor with those 
of Mr. Bumet for 1842, and therefore cannot yet be considered as a universal 
consequence of the application of this substance as a top-dressing. 

111. The experiments of Mr. Burnet, of Gadgirth, have already been partiEdly 
detailed in tlie text (Lecture XVI., p. 363), and tlieir value explained. They 
are important, chiefly, as showing — ■ 

1°. Economical mixtures. — That mixtures can be prepared which, upon some 
soils, surpass gitano in efficacy and in economical value, at its former price. 
The price being now reduced, other experiments are required, yet still the less 
effect of guano upon the wheat crop is in accordance with the results of Lord 
Blantyrc. A wet season, however, may alter the numerical relation which 
these results exhibit. It will be observed that here also TurnbuU's guano pro- 
duced no sensible effect. 

2°. Ejfect of soda. — The efficacy of the salts of soda, whether the sulphate, 
tlie nitrate, or common salt, upon Mr. Burnet's land, are also very striking — 
half a hundred weight per acre of either producing an additional increase of 
about 10 bushels of grain. 

3°. Yield pf Jiour. — Into his tabulated results, Mr. Burnet has introduced a 
new element, and, as it seems to me, an important one in an economical point 
of view, namely, the qiia^ntity of fine jiour yielded by equal vmgh/s of the several 
samples of grain.. The differences presented in this column are very striking. 
Thus lOO lbs. of the grain reaped from the plot which was — 

Undressed, gave 76i lbs. of fine flour. 

Dressed with guano ' 6Sf lbs. " 

With sulphate of ammonia 66 J lbs. " 

With sulphate of ammonia and nitx'ate of soda . . . 54| lbs. " 

It would be interesting to learn from an experienced miller to what extent 
such differences aflfect the money value of the grain to the manufacturer of 
flour. 

4°. Amomit of gluten. — Through the anxiety of Mr. Burnet to draw as much 
information as pos.sible from his excellent experiments, I am able to present 
another feature in regard to the action of these saline and other substances upon 
the qaaliiy of the produce. 

It is known that the quantity of gluten contained in diflferent samples of 
flour is very unlike, and that the nutritive property of the flour depends, to a cer- 
tain extent, upon tliis quantity of gluten. It has also been stated, as the result 
of experiment, that the grain which is raised by means of manure containing 
the largest quantity of nitrogen, is also the richest in gluten. With a view to 
these questions, Mr. Burnet transmitted to me a pound of each of the samples 



No. VIII.] EXPERIMENTS UPON WHEAT. 71 

of flour (see Appendix, p. 5), and upon examination I found them to contain 
the following proportions of gluten : — 

Water per cent. Gluten per cent. 
No. 1. No apphcation 16-3 9-4 

2. Guano and wood-ashes 1615 93 

3. Artificial guano and do 16-8 9-6 

4. Sulphate of ammonia and do 16*4 105 

5. Do., do., and sulphate of soda 157 97 

6. Do., do., and common salt 15*7 9"6 

7. Do., do., and nitrate of soda 16-4 10*0 

8. TurnbuU's guano, gypsum, and wood-ashes . 15-2 9"1 
These results are not without their interest, for though they do not show any 

striking difference in the per-centage of gluten, yet upon the whole the result is 
in favour of those samples to which the sulphate of ammonia* had been ap- 
plied. One of these, No. 4, exceeded the undressed grain by about one per 
cent., or one-ninth of the whole gluten it contained. Were the amount of this 
gluten alone therefore to determine the feeding quality of the grain, this sample 
might be considered as considerably the most nutritious. But besides the re- 
lative proportions of fine flour which they severally yielded, there are other im- 
portant considerations which bear upon this question, and must influence our 
judgment. These considerations it would be out of place to present among the 
present observations. They will be found stated in the text of the Lectures, 
(XIX., p. 498 et scq.) where we treat of the composition of wheat and other 
varieties of grain — and of their respective values in the feeding of man and other 
animals. 

F. — The Experiments upon Grass. 

I. The experiments of Mr. Alexander are not very remarkable or conclusive. 
The meadow, which was drained moss full of timothy grass, gave naturally 1 
ton 4 cwt. of hay, whereas the one dressing raised the produce to 1 ton 8 cwt., 
the other to 1 ton 11 cwt., per imperial acre. The cost is not stated. 

II. But those of Mr. Fleming are very interesting. By referring to page 17 
of this Appendix, it will be seen that in 1841 Mi'. Fleming obtained a greatly 
increased produce of hay by the use of nitrate of soda. He informs me that 
in making the present experiments he was desirous of again testing the eflicacy 
of this salt upon grass, on the same kind of land, and of comparing it with that 
produced by other saline substances. He selected also a portion of the same 
field, on another part of which the trials upon wheat had been made in 1841 
(see Appendix, p. 19), with the view of ascertaining if any analogy could be 
traced or difference detected, between their action in 1841 upo7i wheat, and. their 
effect in 1842 on sown grasses — rye-grass, timothy, and red clover. Both objects 
have been in some measure attained. I shall first present a summary of the 
results. 

OP HAY. INCREASE. DECREASE. 

tons cwt. tons cwt. tons cwt. 

The undressed soil produced ..18 5 

Sulphate of soda, 3 cwt. ... 1 3 

Nitrate of soda, 1| cwt 2 10 12 

Sulphate of soda, 1 cwt ^ , « ^ 

Nitrate of soda, h cwt S 

Common salt, 3 cwt. ..... 1 6 2 

Common salt, 2 cwt ^ i io n a 

Soot, 16 bushels J 1 i^ U 4 

Sulphate of ammonia, 1 cwt. . . 1 13 5 

Guano, IJ cwt 1 18 10 

* It will be borne in mind that this is TurnbuU's sulphate of ammonia, already advert^ 
to in page 61 of this Appendix. 



72 EXPERIMENTS UPON GRASS. [AppeTUUx, 

A mixture of silicate of potash with gypsum produced no sensible effect, 
neither did Turnbull's artificial guano. 

1°. In this repetition of his experiment, therefore, the nitrate of soda on si- 
milar land again increased greatly the produce of hay — giving, at the first cut- 
ting, an excess of upwards of 1 ton, at a cost of 30s. 

2°. But on comparing this action of the nitrate upon grass with its action in 
the same field the previous year upon wheat — we find that though it considera- 
bly increased the crop of wheat, yet every additional bushel raised cost 12s. 6d. 
as the price of the nitrate added to the land (Appendix, p. 19). It appear^, 
therefore, that upo7i soils where the nitrate will not pay when applied to wheat, it 
may yet pay well when applied to grass. 

3°. Again, we find above that 3 cwt. of common salt lessened in a slight de- 
gree the crop of hay, while, in 1841, 1^ cwt. increased considerably the produce 
of wheatin the same field — the additional grain reaped from the salted portion cost- 
ing only 6d. a bushel (p. 19). It would appear, therefore, that on soils where 
amimon salt can be projilably used upon wheat it may do injury upon hay. The 
only circumstance that renders this deduction less safe is that 3 cwt. of salt per 
acre were applied to the grass, which may have been too much considering the 
dryness of the season. 

4°. The latter remark applies also to the sulphate of soda which was laid on 
at the rate of 3 cwt. per acre. A less addition might possibly have aided the 
crop. Yet the negative influence of this salt seems great, since \\ cwt. of nitrate 
— itself tending to increase the crop — was unable entirely to ovei'come the dimin- 
ishing influence of 1 cwt. of sulphate. 

But the reason of this apparent inefficiency of the nitrate, when mixed with the 
sulphate, is in some measure explained by the remarkable fact, that on both of the 
patches to which the sulphate of soda loas applied., the grass that came up consisted 
almost entirely of red fescue (Festuca Rubra), thoxigh rye grass, thnothy, and red 
clover were the only grasses sown. The sulphate, therefore, must first have checked 
or entirely destroyed the grasses which had already sprung up, and, then have 
incited the dormant seeds of fescue to germinate, before the fertilizing agency of 
the nitrate could come into play. 

This effect of the sulphate, should it be confirmed by later experiments, will 
establish the important theoretical principle, that those substances which, when 
present ituhe soil, will destroy some of our cultivated grasses, will encourage the 
growth of others ; and the no less important practical truth, that saline substan- 
ces exercise such a special action on the several crops we grow that we may 
hope to discover the means of aiding tlie growth of the one or the other at plea- 
sure, and it may be at little cost. 

Suiigestion IX. — It is to be recollected that in the case of Mr. Fleming's 
field it may have accidentally happened that the seeds of the fescvie particularly 
abounded in those plots to which the sulphate was applied. With every dis- 
position, therefore, to advance as rapidly as we possibly can, I think it better 
to suspend our judgment upon this point — until the following two series of ex- 
periments shall have been made in two or three different localities : — 

a. By top-dressing any of the ordinary grasses sown — excluding the fescues 
— on four or more plots, with h, cwt., 1 cwt., 2 cwt., and 3 cwt. of sulphate 
of soda respectively, and marking the kind of grasses that iTiost abundantly 
spring. 

b. By sowing half an acre of one or more of the fescues, and especially the 
Rubra, and noting the effect of the sulphate applied in similar proportions upon 
as many patches as before. 

These experiments, it is obvious, would be rendered more interesting were 
nitrate of soda, alone and mixed with the sulphate, tried on other plots, and on 
both varieties of grass. I trust Mr. Fleming, whose educated eye enabled him 
to detect the interesting fact in question, may be induced himself to prosecute 
the subject by further experiments. 

5°. Suggestion X. — We have already seen in the above joint action of the 



No. V7//.] EXPERIMENTS UPON GRASS AND MIXED CROPS, 73 

nitrate and sulphate, another illustration ofthekindof struggle we may suppose 
to go on between substances tending; respectively, the one to increase, the other 
to diminish, the produce. In the jomt action of the common salt and the soot, 
when applied together, we have a further instance of the same kind — an increase 
of 4 cwt. only being caused by the application of 16 bushels of soot, when coun- 
teracted by an admixture of 2 cwt. of common salt. Applied alone, the increase 
of produce would probably have been greater. Will any one undertake exper- 
iments with the view of further bringing out this interesting mutually-counter- 
acting influence of different applications'? 

6°, I can only call attention to the large yield of hay naturally obtained from 
that part of the field on which barley dressed with bone-dust in 1841 had previ- 
ously grown : Mr. Fleming informs me that no sensible difference in the produce 
of hay was observed between the undressed part of the field and that upon which 
the dre&sed wheat had grown in 184], though the crop was not set apart or 
weighed, as we might wish it to have been. 

III. Since the preceding experiments went to press I have received the fol- 
lowing short notice of trials upon hay made by Mr. Campbell, of Islay : — 

" It is very difficult to get the tenants in our wild part of the world to e.xpend 
money in the purchase of foreign substances, however beneficial ; and for this 
reason I have been induced to try the substances mentioned below, because, 
with the exception of sulphuric acid, the others are to be got in abundance 
in the island — the pigeons' dung may be got in large quantities in the caves, 
sea- ware on the shore, and lime is abundant and excellent in quality. The ex- 
periment was made thus — 

WEIGHT IN POUNDS. 

Fresh cut. Dry. 

1. Nothing 240 199 

2. Pigeon Dung 318 275 

3. Sea-ware, Lime, and Sulphuric Acid . ^ . 306 269 

4. Lime and Sulphuric Acid 293 256 

1. A field of about ten acres, lately improved from heather, was chosen; the 
field was well drained and deep ploughed, so as to raise the subsoil (red loam) 
with the moss. On its surface the grass was sown down with oats — 8 cwt. of 
each substance was used to the acre. Eight yards square carefully measured 
from the centre of each variety, and weighed the day they were cut, and again 
on the day they were put into stack. The hay was fully ripe when cut. 

2. The pigeon dung, which looks like peat-dust, was laid on exactly as it 
was taken from the cave. 

3. One ton of lime-shells was mixed with 12 tons fresh sea-ware; after being 
twice turned, the whole of the sea-ware was consumed, leaving only small black 
particles mixed with the lime : the bulk was reduced to five large carts (not 
weighed) ; 4 galls, sulphuric acid, mixed with 400 galls, of water, were added to 
the powder — a violent fermentation took place, and the bulk was further re- 
duced about an eighth. 

4. A ton of lime-shells was prepared according to your recommendation 
slaking the lime with the dilute acid. 

N. B. One measure of this lime in shells gives three and a half in powder." 

G. — The Experiments upon Mixed Crops. 
Mr. Alexander's experiment upon a field of mixed oats, beans, and peas, is 
very deserving of notice, and will. I have no doubt, be repeated. Not only did 
the mixture of gypsum and common salt increase the ultimate produce — but, as 
Mr. Alexander says, it acted like magic — imparting life and vigour to an appa- 
rently dying and worthless crop. 

H. — The Experiments upon Beans, 
I. The principal fact of importance in the experiments of Mr. Alexander is 
the effect he found hie mixture of gypsum and common salt to produce upon the 

E 



14 



EXPERIMENTS UPON BEANS. 



[Appendix, 



beans even wlien already injloicer. This is another of those new and practical- 
ly valuable observations which, year by year, are sure to present themselves to 
our observing experimenters as their inductive researches are continued. 

II. I am happy in being able to introduce here, though it reached me too late for 
insertion among the other tables, the following digest of results upon beans, ob- 
tained upon Lord Blantyre's farm at Lennox Love. The object of them was 
to ascertain the relative effect of ccr lain saline manures, and of rape-dust, and 
guano, upon leans, after a crop of oats. 

Experiments upon Beans, after a crop of Oats, The quantity of land in each 
plot was one-eighth of an imperial acre. Seeds sown 25th February ; manures 
applied 13th May ; crop cut 8th August; stacked 1st September, 1842; and 
thrashed 6th February, 1843. 



No. 



FORDHILL 

FIELD, 

LENNOX LOVE. I 

I ^ 

Description of I -^ 
Dressing. 



Common Salt 
Common Salt 
Rape-dust . . . 
Nitrate of Soda 
Nitrate of Soda 
Rape-dust . . 
Nitrate of Soda 
Sulph. of Soda 
Sulph. of Soda 
Sulph. of Soda 
Rape-dust . . 
Rape-dust .. 

Guano , 

Nothing ... 
Soot 



lbs. 
14 

112 ( 
14 

112 S 

li 

14 

112 ( 
224 

28 

4bsh. 






■^ U 



s. d. 

4 

7 
3 1 



2 
1 

7 

14 
5 

4 



OS. 

lbs. 

588 

630 
672 
644 

686 

700 

700 

700 
728 
672 

1 666 



Weight taken from 
Thrashing Mill of 



lbs. 
231 

265 

276 

250 

282 
282 

289 

292 
230 
248 
234 



lbs. 
54 

53 

63 

59 

60 
73 
65 

61 

68 

85 
87 



lbs. lbs 
2&5 225 



318 
339 
339 

342 

355 

354 

353 
348 
333 
321 



230 
254 
253 

258 

261 

261 

260 
263 
265 
281 



o <u 

i2 & 

.-? c 

O 3 

lbs. 

78 

82 
79 
52 



84 

85 

87 
117 
74 

84 



lbs. 
65i 

66i 

66| 

66* 

66i 

66i 

67 

66| 
66A 
66| 
66 



as 

bushs. 
3-638 

4-000 

4 134 

4210 

4-256 

4-240 

4 313 

4-374 
4-210 
3-720 
3 545 



Increase 

of 
produce 
in grain. 



De- 

crease of 
produce 
in grain 



bsh. 

-282 
•414 
-490 

-536 

-520 

593 

•654 
•490 



lbs. 



bsh. 
•182 



•175 



Remarks. — The soil of Fordhill. on which they grew, is light and of inferior quality — the 
subsoil is of indurated clay, interspensed with boulders and small stones, and occasionally 
beds of gravel. The field was drained every furrow previous to its being broken up from 
old lea in the winter of 1840 — ploughed deep and subsoiled in the autumn of 1841, and ma- 
nured with farm-yard dung in the drill before sowing the beans in the spring of 1842. O-vving 
to the di7ness of the season, the beans were rather short in the straw; the specific manures 
were applied after the plants had attained some inches in height. 7%e sulphate of soda (dry, 
not hi crystals) blackened and destroyed the under leaves, ttherever il came in contact with 
them, but fresh shoots soon appeared, and it did not seem permanently to injure or retard the 
growth of the plants. They did not, after the application, sliew any marked "change of colour ; 
and at no period did they seem to differ much from the rest of the field. A few peas were 
sown among the beans ; and in dressing the grain, an attempt, partially successful, was made 
to separate them— each experiment underwent the same process in the dressing. Grain 
column 1st represents the produce in beans— grain column 2nd represents that in peas. 
The separation, however, not being completely effected, there were left peas among the beans, 
and some of the smaller and inferior beans among the peas. I thougiit a distinction of this 
kind worth making in the Tables, as I observed that some of the lot.s contained much more 
peas than others, and conceived that the relative value of the manure, as applied to either, 
might thereby in soiie measure be shown, as well as their effects on the beans alone more 
truly exhibited. The gross weights were taken, as those of the other experiments, at the 
town of Haddington's weighing-machine, before thrashing — the detailed weights and mea- 
Burements by myself. Wm. Goodlet. 

The produce of the undressed part amounted in the above experiment to 29 J 
bushels, and it is remarkable — 

1°. That the soot alone caused a sensible diminution of the gross produce, 
and alone did not lessen the proportion of peas. 

2°. Although the season was so dry the sulphate of soda gave a larger increase 
than was obtained by the addition of twice its own weight of guano. 

3°. That an admixture of half its weight of nitrate with the sulphate of eoda 



No. VIIL] EXPERIMENTS UPON BEANS. 75 

did not increase the produce beyond that of an equal weight of sulphate alone. 
This is different from the action of the latter salt in the case of the other grain 
crops and of potatoes. 

4° . That 1 cwt. of sulphate of soda produce as great an effect as 16 cwt. of rape- 
dust — the quantity of grain reaped from both applications being very nearly the 
same. 

SiiSs:estion XI. — These striking effects of the sulphate ultimately took place, 
although when first applied to the young plants it burned and blackened their 
leaves. I trust that these results will also be tested by repetitions in other years 
— less droughty, it is to be hoped — and in other parts of the country. For the 
sulphate of soda, Mr. Alexander's expei-iment seems to say that gypsum, which 
is still cheaper, may be economically substituted. 

5°. It will be seen that guano upon this crop, as upon the wheat already noticed 
(p. 68), was less successful than some of the other substances employed. 

Conclusion. — Upon the observations of Mr. Gardiner in regard to the effect 
of the dressings of 1841 upon the crop of 1842, I have nothing to add to the re- 
marks I have already made (p. 57) upon their importance, and upon the good 
that must follow from continuing them. But in concluding these observations, 
the reader will please to recollect that I have adverted to those points only, in the 
above tables of results, which appeared to myself most important. There are 
many other points to which by a careful study of the tables his attention will 
naturally be drawn. He will consider the observations themselves also, as 
only so many gropings after truth. The present state of our experimental inqui- 
ries can scarcely be supposed as yet to give us more than a glimpse here and 
there of the true light. Like a man who finds himself in a dark dungeon, we 
are peering through the comparative gloom of our prison-house, in the hope of 
finding some mode of escape into the upper day. Like him we may be long in 
discovering the true outlet, and the passage upwards may be narrow and in- 
tricate ; — but the same conviction which will give him safety, will ultimately 
lead us also to the light — that he who persists in trying — marking and recollect- 
ing every turning he has explored — may at length escape; but that he who sits 
still, in indifference, or gives up his quest in despair, is sure to die in darkness. 



No. IX. 

ADDITIONAL EXPERIMENTS IN PRACTICAL AGRICULTURE, 
MADE IN 1842. 

The following experiments were made at Erskine, in Renfrewshire, upon the 
Home Farm of Lord Blantyre: — 

Experiment I. — Potato Oats, after old Grass. 
The soil was variable, chiefly good loam, resting on a subsoil partly gravel 
and partly sand. The field, having been long in pasture, in many places very 
wet, was drained in November and December, 1841; ploughed soon after, and 
sown with oats on the 8th of April. The manures were applied on the 15th 
of April, and harrowed in with a single stroke of the harrows. One-fourth of 
an imperial acre being previously measured off for each plot. 

According to notes taken of the appearance of the crop from time to time — 

May 23. — The nitrate of soda (No. 1) looking darker in colour than any of 

tlie other plots; next to it, in point of colour, the foreign guano (No. 5) seems 

best; then the soot (No, 9^; then the sulphate of ammonia (No, 2); cannot, 

however, discern any very aecided difference in the appearance of the others. 



76 



EXPERIMENTS UPON OATS AND GRASi8. 



[Appendix, 



May 30. — There appears a slight difference in favour of all the applications 
in the order above stated, the sulphate of soda (No. 3) pale in colour. 

June 28. — Appearance same as on 30th May, 

The crop was cut 19th and 20th of August, and thrashed from the stock on 
the 7th of September ; the results carefully ascertained, the grain by weight and 
measure; the straw by weight, as it came from the thrashing-machine; no ac- 
count taken of the chaff. 

RESULTS OF EXPERIMENT 1. OATS. 



No, 



Applications. 



Nitrate of Soda, 28 lbs 

Sulphate of Ammonia, 28 lbs. . . 

Sulphate of Soda, 56 lbs 

Nothing 

Foreign Guano. 28 lbs 

Tumbull's BritishGuano.56 lbs. 
TurnbuU's Impr'd Bones, 56 lbs. 
Tumbull's Humus, lUbush. ... 
Soot, 10 bush .' 



5-c s- 



r^ TO *.- 



s. d. 

6 3 

5 

3 

6 3 

4 
3 

10 
2 11 



PRODUCE. 



Good grain. 



bsh. lbs. 

12 21 

12 22 

12 — 

12 10 

12 4 

12 17A 
11 2" 
11 8i 

13 30^1 



lbs. 

42i 

40 

40 

41 

41 i 

4H 

41 

41 

41 



Light grain. \ 



lbs. 

8 
10 
Uh 
\Qk 

6J 
lOi 
10| 
111 

9i 



OD 



lbs. 
908 
770 
762 
717 
768 
788 
675 
644 



Increase + 


or 
Decrease — . 


Grain. 


Straw. 


lbs. 
+26h 

—18 


lbs. 
+191 
+ 53 
+ 45 


+ 6 
--14 
-49 
+41 
—60 


+ 51 
+ 71 
-42 
— 73 
+163 



Experiment II. — On Old Pasture Grass lobe cut for Hay. 

The soil was of medium quality, on stony clay subsoil. The part of the 
field experimented on was originally very wet, producing scarcely any better 
herbage than rushes and other semi-aquatic plants, was drained in 1835, has 
been three years pastured after a crop of hay from young grass in 1838 ; the 
soil is of a blackish friable texture, the subsoil very retentive. The specific 
manures were applied on 15th April, vi'ith the exception of the soot, which was 
sown on the plot in the experiment at the same time that the other parts of the 
field were dressed whh soot, being about the middle of March, and by the 
15th of April were shewing a greener shade than the portion left for experiment. 

April 25. — Observed the ridge or plot No. 5 (sulphate of ammonia) looking 
dark in the shade, and that the salt has burned the leaves of daisies and other 
broad-leaved plants ; the moss or fog seems also to be burned, it looks black 
and unhealthy. 

May 7. — The ridges or plots Nos. 2, 5, and 7, look decidedly better than the 
rest ; No. 3 also seems farther advanced than where no applications were made. 

May 23. — No. 2 getting on very fast, and now looks as well as No. 1, which 
has always had the advantage (to appearance) of the other plots. The grass 
on No. 3 pale in colour, but taller than where no manure was applied. 

The hay was cut on the 3d of July, and the grass weighed soon, i. e., in a 
few hours after being cut down, but being very sunny weather it was somewhat 
faded when weighed. The made hay weighed and put into stack on . 

Each plot consisted of one-fourth of an wiperial acre. 

RESULTS or EXPERIMENT II. — HAY. 



No. 



Applications. 



Soot, 10 bushels 

Nitrate of Soda, 40 lbs 

Sulphate of Soda, 80 lbs 

Nothing 

Sulphate of Ammonia, 40 lbs. . . . 

Nothing 

Foreign Gnano, 40ib3 

Tumbull's British Guano, 80 lbs. 



Cost of 
applica- 
tion. 



d. 
11 

3| 
lU 



PRODUCS. 



Grass, j Hay. 



lbs. 
2:331 
2536^ 
19.36 
1760 
2516J 
2374 
3024 
2841 



lbs. 
970 

10261 
841* 
726 
935 
838 

1190 

1044 



Increase 
in Hay. 



lbs. 
188 
244i 
59| 

153 

408 

asg / 



No. IX.] 



EXPERIMENTS UPON WHEAT AND POTATOES. 



77 



N. B. — I take the average of the two plots which had no manure, as the sura 
to deduct for finding the increased produce. The second column from the 
right is made hay, the third is green grass, weighed soon after being cut. 

Experiment III. — Up07i Wheat. 

Soil, a good strong loam, resting on a heavy subsoil composed of clay and 
small stones, called till. The wheat was sown in November, 1841, after a crop 
of potatoes. The field had been long in grass previous to 1840 — when it was 
drained, and ploughed for oats in the spring of 1840 — was well dunged with 
good farm-yard manure, and was also limed for the potato crop of 1841, so that 
the field was in very good condition for wheat. 

The manures were applied 14th April, 1842, and harrowed in with a stroke 
of the harrows. 

May 10. — The portion No. 1 seems darker in shade than No. 9 and No. 8. 

June 28. — A calm day, with gentle rain — many of the lots much bent down, 
as follows : — No. 1 much bent down. No. 2 partly swirled and bent at the 
end next a planting. No, 1 swayed at east end next the planting, not so bad as 
No. 2. No. 4 less bent down than No. 3. No. 5 much bent down and swirled. 
Nos. 6 and 7 all standing. No. 8 partly laid down. No. 9 very much swirled 
and laid. All the laid wheat came up again in a few days after the rain. 

The wheat was reaped with the sickle, and in due course stacked, in good 
condition. It was thrashed on the 8th February, 1843. 





RESULTS OP EXPERIMENT III. 


WHEAT. 






No. 
1 
2 
3 
4 
5 
6 
7 
8 
9 


Applications. 


STRAW. 


GRAIN. 1 


Total 
quan- 
tity. 


Increase + 

or 
Decrease — . 


Total 
quantity. 


Weijtht 

per 
bushel. 


Increase. 


Soot, 10 bushels 

Turnbull's Humus, 10 bushels. .. 
Improved Bones 


lbs. 
1213 
1055 
973 
1193 
1049 
1008 
1073 
1138 
1159 


lbs. 
+ 205 
+ 47 
— 35 
+ 185 
+ 41 

+ 65 
+ 130 
+ 151 


bush. lbs. 

13 33 

12 48 
11 58 

14 43 
11 34i 
11 1 

13 7 
13 38 
13 38 


lbs. 

58 

60 

62 

61 

61J 

62 

62 

62 

62 


bush. lbs. 

2 32 

1 47 
57 

3 42* 
33i 

2 6 
2 37 
2 37 


Turnbull's British Guano 

Foreign Guano 


Nothinor 

Sulphate of Soda 


Sulphate of Ammonia 


Nitrate of Soda. 



Experiment IV. — On Potatoes. 

Soil, a medium loam, resting on gravel and sand. The field was ploughed 
from old grass, and sown with oats in 1841 ; was drained (where wet) and deep 
ploughed in the autumn of 1841 ; prepared for potatoes in the spring of 1842, 
and well dunged at the rate of about 45 tons of very good dung from Glasgow, 
per acre. The manures were applied in addition to the dung, by bei7ig sprinkled 
above the dnng in the drills before placing the sets, then covered by reversing the 
drills, on the 21 st and 22d of April, 1842. 

During the season could discover little or no difference in the appearance of 
the portions dressed with the specific manures, from where no applications 
were made ; the crop was a very equal good one over all the field. One-fourth 
of an imperial acre in each plot. 

' I can ill reconcile the great produce from No. 4 with the appearances when growing, 
and have been suspicious, that notwithstanding every precaution being taken to avoid mix- 
ing, some sheaves of No. 5 plot, have been taken to No. 4, while the crop was in stook, as it 
was sometimes necessary (during the time the stooks were in the field) to have them re- 
paired, they being blown down once or twice. 

The cost of the applirations, as also the quantities applied, of the different materials, were 
the same as in Experiment No. I., on Oats. The light grain is not here taken into account, 
as it was too trifling in quantity and quality to be of any importance, and nearly the same ia 
every case. 



78 



EXPERIMENTS UPON POTATOES. [Appendix, 

RESULTS OF EXPERIMENT IV. ON POTATOES. 



No. 
1 



Manures. 



Cost. 



PRODUCE. 



^Nii 



Nitrate of Soda 14 lbs. 

Ipbate of Soda '2R Ihs. 

Sulphate of Soda 2S lbs. ( 

Sulphate of Ammonia 14 lbs. \ 

Foreif^n Guano '28 lbs. 

TurnbuU's British Guano 56 lbs. 

Soot, 7h bushels 

Improved Bone?, TurnbuU's, 56 lbs. 

Gypsum, 1 bushel 

Nothing 



s. 


d. 


4 


7h 


4 





6 
4 
2 
3 


3 







— 



tons. cwt. qrs. lbs 





19 


19 
15 
19 
18 
19 



2ih 

2^ 


21 
21 
21 
21 

7 



Increase + or 
Decrease — . 



cwt. qrs. lbs. 
+ 1 I 17 



+ 

+ 

+ 

— 3 
+ 

- 



17* 



The gypsum used turned out to be genuine on analysis.* 



REMARKS UPON THE PRECEDING EXPERIMENTS. 

1°. Effixt of the drovghl. — It is to be observed, in the first place, that the 
great drought of the season exercised an unfavourable influence upon the re- 
sults of these experiments also. It is necessary, therefore, to suspend our judg- 
ment in some measure regarding them — until -future experiments in other sea- 
sons shall confirm or modify them. 

\f. Inferences to be drawn from the colour of the crop. — A new feature in- 
troduced by Mr. Wilson in the account of these experiments, is the appearance 
presented by the several crops at different specified periods after the dressings 
were applied. 

It is a common thing for practical men to estimate the relative produce of 
different fields or parts of the same field by their appearance, and especially by 
the colour of the growing crops. Yet that this is not to be depended upon in 
a corn crop, is proved by the observation that up to the end of June appearances 
in the oat field were most in favour of the nitrate of soda, the guano being se- 
cond, and the soot third in order. Yet, when reaped, the — 

Nitrate gave an increase of only 2^ bushels per acre. 

Guano 24 lbs. per acre. 

Soot 6 bushels per acre. 

The nitrate did give a little more straw than either of the other two, but that 
the colour is not an unfailing criterion even as to the produce of straw or of 
hay is shewn by the experiments upon oats and upon hay. In both of these 

* List of prices paid for the manures used in the foregoing experiments : — 

1. Foreign Guano 253. per cwt 

2. TurnbuU's Guano 8s. " 

3. TurnbuU's Improved Bones 6s. " 

4. TurnbuU's Humus Is. per bushel. 

5. Nitrate of Soda 25s. per cwt. 

6. Sulpliate of Soda (dry) 6s. " 

7. Sulphate of Ammonia 20s. " 

8. Soot 3id. per bushel. 

Nos. 2, 3, 4, and 7, were manufactured and furnished by Turnbull and Company, Chem- 
ists, Glasgow. The British (Guano No. 2) is said to be made up as follows : — 

2 cwt. of Sulphate of Soda. 
2 cwt. of Sulphate of Ammonia. 
1 cwt. of Common Carbonate of Soda. 
15 cwt. of Improved Bones, manufactured by Turnbull & Co. 

20 cwt., or 1 ton. 

The Improved Bones are said to be half dissolved bones and half wood-charcoal. I be- 
lieve the bones include animal matter, as I am informed the carcaises of old horses, &c., 
are all used in the manufacture. James Wilson. 

Preeland, Erskine, 20th February, 1843. 



No. JX.] REMARKS UPON PRECEDING EXPERIMENTS. 79 

crops the portions dressed with sulphate of soda are described as pale in coloujy 
and yet the excess of produce over the undressed parts was as follows : — 

In the oats . . ^ cwt. straw. J where the sulphate was applied. 
In the hay . . 2 cwt. per acre, J ' /^ 

The increase in neither case would be deserving of much attention — except 
as showing satisfactorily that M^rong conclusions may be drawn in regard to 
the efficacy of manures and top-dressings by those who judge only by the eye 
— and that safe reliance can be placed on those comparative results only which have 
been tested by weight and vicasure. I know, indeed, that practical farmers who 
have applied nitrate of soda to grass land, and have been delighted by the beauti- 
ful green colour which followed, have occasionally been disappointed by find- 
ing that after all this promise the weight of hay obtained was no greater than 
upon the undressed parts of their fields. As to the feeding qualities of the two 
kuids of hay no experiments have yet been made, though it is known that cat- 
tle prefer that which has been dressed. 

Suggestion A'/.— I put down, therefore, as a distinct suggestion for the pur- 
pose of drawing attention to the subject, that this plan of specially noting the 
appearance of the crops at stated, say monthly periods, should be adopted in all 
future experiments. This will serve, not merely to show us more clearly what 
kind of appearances are to be trusted, and how far, as indications of an increase 
of crop— but may hereafter prove of further importance when experiments shall 
begin to be instituted upon the feeding properties of crops reaped under dif- 
ferent circumstances, and raised under different kinds of management. 

3°, Importance of having two or more experimental plots similarly treated. — 
The experiments upon hay above-mentioned exhibit another illustration of the 
fact adverted to in page 59 of this Appendix under the head of li7}iits of error. 
I there drew the attention of experimenters to the difference in the produce ob- 
tained on two equal patches of the same field of turnips, to neither of which 
any dressing had been applied. At Erskine two equal plots of grass in the 
same field gave a similar difference of produce. I present both results here for 
the sake of clearness. The produce per imperial acre was— 

Ilay at Erskine. Turnips at Barochan. 

tons, cwt tons. cwt. 

1st plot 4 5 ^^ ^I 

2d plot 3 3 U_ 

Difference 12 19 

In my remarks upon the difference between the two plots of turnips (Appen- 
dix, p. 59), I expressed an opinion that differences equally great, depending not 
at all upon the substance applied, might be expected on equal portions of those 
fields upon which our different saline manures may have been applied ; — and 
that very erroneous conclusions might thence be drawn in regard to the abso- 
lute and comparative effects of the substances with which our experiments are 
made upon the crops to which they are applied. 

I have since met with a confirmation of this view in a record of two pairs of 
experiments made with equal quantities of rape cake upon equal plots of red 
wheat, in the same season, and upon adjoining parts of the same field, (British 
Husbandry, I., p. 112.) The results of two experiments with different quan- 
tities of rape dust were as follows : — 

Produce of L'gnt 

Rape dust applied, market com. Weight per bushel. com. 

stones. bush. lbs. oz. Iba. 

1st plot 594 ... 26 ... 52 10 ... 46 

2nd plot 59i ... 21 ... 50 8 ... 67 

Istplot 86 ... 28 ... 53 4 ... 35 

2nd plot 86 ... 22 ... 51 2 ... 91 ^ 

The differences both in the quantity and in the weight of the grain reaped, w 



^^ REMARKS UPON preCbding EXPERIMENTS. [Appendix, 

each of these pairs of experiments.are so great that had they been ohtained from 
plots of ground dressed with different manures we should readily have ascS 
them to the unhke action of the substances we had applied. Do^,btrmarnatu- 
rally arise, jhei^fore when we look at the several tables of results contained hi 
this Appendix how far the differences presented in them are really due to the un- 
hke action of the manures employed, and how far to natural causes no^hther^o 
mvestigated. Can al the experiments made during these last two yean w kh so 
much care really be vitiated by this source of error°1 The point mus brelicT- 
dated by further experiment. Should it prove that we have heie a general 
source of error, it is satisfactory at least that sVe have discovered it at thethSoTd 

" aV:Smf it in fSr "^"^"^"^^^ '''^''''' ^"^ ''^' ^ can^devVse'meat 
I therefore repeat the 'Suggestions I. and II., which I ventured to offer in pa-e 
69 (Appendix), thatsome of my readers, of whom I believe many are interested 
m his subject, would in the ensuing season ascertain accurXry^.Wodu^^^^^^^^^ 
equal measured quantities of the same field, under whatever crop irmav be 
and publish or transmit the result to me-and that in all future exnenLm: 
made with the view of ascertaining the effect of different nlirrupon^an^^^^^^^^ 

the ave ie m?^in^ I 'TT^ V^^'^ ^^'^^'"^'^ ^^^^ ^^^^^ substance taken as 

^nS&velxSnlarai^^^^^^^^^^ -' ^-^^^^ -^^^ ^^ 

sidtrallt'7hpCri"r^"/^'''' experiments a top-dressing of soot increased con- 
T^J^^.^, produce of oats and wheat, while it diminished the produce of oo- 

T:i:iz::tit::^i^:^''^''' ^'^^ ^^^ p-^- p- -e o^n the^drl^e^d 
Sretr • • i?t ' ' iiPi^- ' • Htor^rcwt. 

Dressed . . 55 bush. . . 54 bush. . . n tons 3 cwt. 

Ihe unfavourable effect upon the potato crop may probably be due to th^ 

mode in which it was applied, as in other distr/cts it is^ieiyrefuno potatoes 

per fere ' TsJ' Mr'^PI?"'- "^^'V^P'^.^^ -'^-^ to turnips,In incrllL'^fron^ 

.^Vll p. iii). ^ • ^^^'"'"g^ Experiments, Appendix, p. 43j also, Lecture 

nAJi7x!"''''^''"l '"'^'"'^'^f'ootand ofmtraU of soda.~i:\,^ immediate effect 
of both these substances is to darken the colour and to increasTthe Growth 
of hay and straw. In this respect the advantage is rather on the side of f he ni 
If^'J^'^" the soot m some cases gives a little" more gra n Thu thft^to^J 
fct^Io^f^heX^l^^^^ 

Hay. Whedt. Oats. 

Soot 7 /.,.,* lA I , Grain. Straw. 

N^-eorsoiaio'::;;;; Jo^S: : ; «,S; ?- 

cj . J Wheat. Oats. 

Sooted ... 58 lbs. . . 4i Jbs 
Nitrated . . . ^^ lbs. . 431 lbs' 



No. IX.] HEMARKB UPON PRECEDING EXPERIMENTS. 81 

yet met with, seem to point — that it is more uniformly successful when applied to 
root than to grain crops. The increase of oats in the present experiment did not 
exceed half a bushel per acre — though that of hay amounted to 14^ cwt. 

7°. Action of sulpiwlc of soda. — I have already noticed the effect which this 
salt has in palvng the colour of the crop, even when the produce of grass or 
straw is increased. In regard to the grain, we see in the experiment upon oats 
that it reduced the crop, If bushels per acre — while the wheat crop was increased 
10 bushels by a similar application. 

Is this difference in its effects due to the nature of the soil, or to the special 
action of the sulphate upon the two crops 1 

We have seen m the experiments made in 1842 at Lennox Love (p. 52), that the 
sulphate of soda diminished the oat crop 15^ bushels per acre — an effect, how- 
ever, which may be mainly ascribed to the great drought in that locality, since 
even nitrate of soda caused a diminution of i2i bushels. But it also diminished 
the wheat crop at the same place to the extent of 9^ bushels per acre, but upon 
this crop also the drought appeared to interfere with the natural action of the sev- 
eral top-dressings which were applied, so that no tnist-worthy conclusion can 
be drawn from the appare7it results of their action. 

Suggestion XII. — I have already suggested (p. 72) an interesting experiment 
with sulphate of soda, in order to test the very curious observation of Mr. Flem- 
ing, that when applied to land sown with artificial grasses, it brought up a crop 
consisting almost entirely of fescue grasses, though none of these had been 
sown. 1 would here suggest further that the marked difference observed at 
Erskine between the action of this sulphate upon wheat and oats should be 
further investigated— with the view of obtaining a satisfactory answer to this 
question — Does sulphate of soda act less favourable upon wheat than upon 
oats in the same soil ] Or does an unlike action manifest itself only when the 
soils are different 1 I fear the suggestion comes too late for the present year, 
unless, as I hope, there are experiments already in progress which will throw 
light upon the question. But the suggestion will not, I believe, be overlooked 
when another year comes round. 

It is further worthy of remark, in regard to the action of the sulphate of soda 
upon the wheat crop, that the straw was stronger and less laid than where any 
of the other dressings were applied. 

8°. Action of sulphate of avimonia. — The substance employed under the name 
of sulphate of ammonia, as I stated in a previous part of this Appendix (p. 61,) 
is not what its name implies. The makei-s, the Messrs. Turnbull, of Glasgow, 
inform me that it is prepared by adding sulphuric acid to fermenting urine, and 
evaporating to dryness*. Though such a substance must vary in composition 
with the urine from which it is prepared, and must contain more or less am- 
monia according to the degree of fermentation which the urine has undergone, 
yet good effects may fairly be expected from it. I here exhibit the effect of 1 to 
i;^ cwt. per acre applied to different crops — 

Unrlressed. Dressed. Made at 

Wheat 44 bush. 54| bush. Erskine. 

Do 31 i bush. 40 bush. Gadgirth. ^ 

Oats 49 bush. 50 bush. Erskine. ' 

Turnips 12| tons. 24^ tons. Barochan. 

Potatoes I2f tons. 14^ tons. do. 

Do 8f tons. 13^ tons. do. 

These results not only recommend this substance to the practical farmer, but 
they also enforce the remarks I have made in the text upon the value of urine 
in general, upon the large waste of manure annually incurred by the neglect of 
it, and upon the virtual money-loss which is suffered by those who allow it to 
escape from their farm-yards. [See Lecture XVIII., p. 463.] 

9°. Action of TiirnbuU's humus. — This humus, as it is called, is night-soil 

• In the text I have deseribed it under the name of auiphattd urine. —^oe p. 461. 



82 RF.MARKS UPON PRECEDINO EXPERIMENTS. [Appendix, 

and urine mixed with charcoal and gypsum, and dried by a gentle heat. Its ef- 
fects upon the wheat crop are, in the present experiments, more favourable than 
any of those I have yet placed upon record, 'i'he following experimental re- 
sults exhibit the nature of its action in two localities, both in the same neigh- 
bourhood : — 

Undressed. Dressed. Experiments made at 

Wheat ... 44 bush. 51 bush. Erskine. 

Oats .... 49 bush. 45 bush. do. 

Turnips . . . 12| tons. 13| tons. Barochan. 

Do. ... 12 tons. 17 tons. do. 

Potatoes . . . 5| tons. lOf tons. do. 

These results, especially those upon the corn crops, are not so beneficial as 
might well be expected from a prepared night-soil, and they afford room for the 
suspicion that the mode of manufacture has been such as to dissipate some of 
the more valuable constituents. 

10°. Experiments upon potatoes. — In the experiments upon potatoes the whole 
crop averaged 12 tons per acre, and the parts of the field to which the artificial 
manures were added exhibited no marked increase above this general average. 
Even the mixture of nitrate with sulphate of soda, which in so many other 
cases has proved beneficial to the potato crop, in this instance produced only 1 
cvvt. of increase. 

It may be that the manure which was added at the rate of 45 tons per acre 
contained a sufficient supply of all those kinds of food which were added after- 
wards in the saline and other substances. If so, a larger crop could only have 
been obtained by the addition of some other substance not tried, for a loam of 
moderate quality ought to be able to produce more than 12 tons of potatoes per 
acre. 

Or it may be that these same artificial manures would have produced a larger 
increase had they been pvit on as a top-dressing after the crop had come up, in- 
stead of being spread upon the manure before the potatoes were planted upon 
it. In the experiments of Mr. Fleming made with especial reference to this 
point, [Appendix, pp. 49 and G6,] it was found that a larger proportionate 
increase was obtained from the same saline substances applied in equal quanti- 
tites to the potato crop when they were spread upoii the vianure, than v:hen Viey 
toere applied as a top-dressing after the crop had come up. Still the experiments 
in his case being made in different fields, I stated that the point was not to be 
considered as established, but was deserving of further investigation. This 
opinion is strengthened by the results of these experiments of Lord Blantyre : 
I would therefore beg to offer as — 

Svggestian XIII. — That the application of saline manures to the potato 
crop — either when the trial is made for the purpose of obtaining practical infor- 
mation, which may, hereafter, be valuable as a guide to the operations of the 
farmer, on the land whex-e his experiments are made, or for that of arriving a1 
results which may be theoretically useful — that the same proportions should b« 
applied to two or more plots buried with the manure, and to two or more dusted 
on as a top-dressing. Prom an accumulation of results obtained in both ways, 
we shall be able to extract something like a principle by which practical men 
may be easily guided in that direction which is likely in the greatest number 
of cases to lead to the greatest amount of profit. 

11°. Water in the potatoes. — I will here add one other observation upon the 
potato experiments. There was, as we have already remarked, no notable dif- 
ference in the weight o^ crop raised upon the several patches. But the quality of 
the crop — the weight of dry food i-aised upon the several patches — might really 
be different notwithstanding. In my remarks, [Appendix, p. 65], upon the Baro- 
chan experiments upon potatoes, made in 1842, I have drawn attention to the 
fact that potatoes sometimes contain as much as 30 per cent, of dry food, and at 
other tunes as little as 20 per cent., and therefore that a ton of potatoes of one 
kind may contain 6 cwt., while the same weight of another contains only 4 



I 



No. JX.\ REMARKS UPON PRECBDINO EXPERIMENTS. 83 

cwt. of dry nourishment. It may be, therefore, that as by growing in unlike 
soils or with unequal degrees of rapidity our potatoes may contain different pro- 
portions of water, so by different kinds of dressings which act in the si me way 
as natural differences of soil, and cause the plants to develope themselves with 
greater or less rapidity, the same effects may be produced. One kind of saline 
substance, such as nitrate of soda, by hastening the growth, may give us a crop 
of potatoes containing much water, while another, such as sulphate of soda, by 
retarding the growth, may give a crop containing less water — and thus, though 
tnere may be no difference in the weight of the two crops, they may be very 
unlike in the relative proportions of food they contain. 

If such be the case it is of great practical importance to determine the quantity 
of water which our several experimental potato crops contain, since without 
this we may draw very incorrect conclusions as to the value of our experimental 
manures — placing the highest value upon that which gives the greatest weight 
of raw material, and esteeming least, perhaps, that which produces the greatest 
weight of dry food. 

1 would again, therefore, draw the attention of my readers to the subject of 
Suggestions IV. and VI., [Appendix, pp. 63 and 65,] in reference to the'deter- 
mi nation of the quantity of water in their experimental root crops. The 
method of doing this is very simple, and has already been described, [Appendix, 
p. 64.] 

Each new series of experimental results we are called upon to examine and 
analyse, will, I hope, more and more satisfy my readers, as they do myself, 
that this is the true line of procedure, and that though there may be much in 
our results at first which may appear contradictoiy and discouraging, yet that 
out of these crude results, when combined, compared, and frequently repeated, 
the real substance of a rational agriculture will, slowly it may be and with di^ 
ficulty, yet surely at last, be extracted. 



No. X. 

RESULTS OF EXPERIMENTS IN PRACTICAL AGRICULTURE, MADE 
AT BAROCHAN IN 1843. 

Experiment I. — Upo7v Potatoes. 
Comparative effects of guano, farm-yard manure, gypsum, &c., by them- 
selves and in mixture, upon Potatoes of different varieties, planted 25tn, 26th, 
and 27th April; lifted, measured, and weighed from l2th to 14th October, 
1843. On one-eighth of an imperial acre. 

The portion of the field upon which these potatoes were grown contains 
about five acres ; soil — loam of medium texture, super-incumbent upon trap 
rock. It was trenched with the spade out of seven years old lea in the winter 
of 1842 and 1843 to the depth of 16 inches, the sward being turn-spaded into 
the bottom of the trench, and the subsoil a stiff yellow till brought up to the 
top, which mouldered down to a fine mould during the winter. The drills were 
formed for the potato cuts with the double-moulded plough, and by the 7th 
June the plants were all brairded in the rows, and were worked in the usual 
manner with the plough, drill, grubber, and hand-hoes. After the drills were 
formed, where the guano was used, it was sown in the drills by the hand, on 
the bottom and sides of the drills, the farm-yard manure being then put in and 



b4 



EXPERIMENTS UPON POTATOES. 



[AppeTidix^ 



No. 



8 



Manures. 



Guano 

Farm-yard manure..... 

Guano 

Farm-yard manure 

Farm-yard manure 

Guano 

Farm-yard manure 

Guano , 

Farm-yard manure 

Gypsum 

Farm-yard manure 

Gypsum, powdered on 

sets 

Farm-yard manure..,!. 

Farm-yard manure 

and top-dressed 7th July 

with Guano 

Guano 

Farm yard manure 

Guano 

Guano 

Farm-yard manure 

Farm-yard manure 

Guano 




So 
3 m . 

P «-> o. 



154 

136 
118 
128 

144 



4) I.. 
O O 

s «s 
o c. 

Ph.S 



fc CO 

«J « c 

> o o 



tns. cwt. jE. s. 



19 



38 10 



17 34 
14 15 29 10 
16 32 



18 



120 

106 

98 
86 



122 


15 


5 


112 


14 





116 


14 


10 


130 


16 


5 



15 

13 5 

12 

10 15 



36 

30 10 

28 

29 
32 10 



Perths. 
Reds. 
Rough 
Reds. 
Do, 

Cups. 
Do. 



Do. 
Do. 
Do. 

Buffs. 



30 Do. 

26 10^p^"^J^«- 
Blues. 



24 
21 10 



Do. 
Do. 



spread upon the top of it. Cut sets were then laid on and covered up with 
about three inches of soil. Particular attention should be paid when ^uano is 
ffd thatit be we I mixed with the soil, as this is of the greatest importance to the 
health of the plants and the bulk of the crop, especially in the case of potatoes and 
turnips. This conclusion has been arrived at after three years' extensive ex- 
perience in the use of guano as a manure; as it has been found here that the 
more minutely it is spread and worked into the soil the crop is the heavier and 
the better matured. When it has been used in a body immediately under the 
plan , It has always been found to induce a strong vigorous growth of stems 
and eaves, and, in general, to ripen the plant prematurely, and both the potatoes 
and turnips were in consequence deficient in tubers and bulbs. From these 
circumstances it may be inferred— what is indeed known to be the case— that 
the guano does not contain all the ingredients which are required by the plants 
and that the large proportion of ammoniacal salts it contains— when it is laid 
in a mass in immediate contact with the roots of the plants— pushes on the 
growth too quickly with small stems and delicate leaves. Numerous small 
bulbs are the consequence, and the cultivator being disappointed is led to pro- 
nounce the guano worthless, whilst his inferior crop may be in a great measure 
owing to bad management. Whatever maybe the reason, however, it has 
been found in using it here that ichcn sown broad-cast the crops of every descrip- 
tion have been benefitted, while, on the other hand, lohen laid in a body near 
the roots the reverse has been the case. In cutting the potato for seed, gypsum 
in powder was strewed upon the sets when newly cut, and it will be sein from 
INo. bot the table, with good effects in adding to the produce, as where the cuts 
were so powdered, as in No. 6, their superiority over No. 7 (which was not 
oone so) in point of strength and vigour was most remarkable, and when lifted 
the produce was 1 ton 5 cwt. per acre more than No. 7. It may also in a certain 
measure be a means of preventing failure in the potato, as there was no failure 
m this field where the gypsum was so used on the cuts, while the same seed 
potaloes fai2ed upon another field which was planted at the same time, but 



No. X.] 



EXPERIMENTS UPON POTATOES AND HAY. 



85 



where no gypsum was powdered on the sets. At all events, it is worthy of a more 
extensive "trial as a preventative, and it will in all soils, where it is deficient, 
add to the produce. It has, at the same time, the merit of being a cheap appli- 
cation. 

There was no great alteration in point of strength or forwardness till the 1st 
of July, when all those patches upon which the guano had been used began to 
take the lead of those planted with farm-yard manure alone. The guano produced 
a dark green colour and very strong stems and leaves, so much so, that it was 
found when too late that they had been too near planted, i.e., 32 inches between 
the drills, and 12 inches between plant and plant. There would have been a 
far heavier crop if there had been more space, as the strong growing varieties, 
such as the cups and blues, were nearly choked for want of air. It will be 
seen from the tables that a mixture of guano and farm-yard manure gave a 
greater crop than where either of them was used alone. The portion, iN^o. 8, 
was top-dressed with guano when the potatoes were set up for the last time. 
It was sown broad-cast between the drills, after which the drill harrow was put 
through them and the plough followed, it acted immediately by altering the 
colour to a dark green, the plants putting out, at the same time, new stems and 
leaves, but owing to its being applied so late in the season, there was a larger 
proportion of small potatoes than at the others when lifted. After many trials 
it has been found that the best and most economical way of rising g%iano for the 
potato crop is by adding 2 or 3 civt. per acre to half the tcsual quantity of farm- 
yard dung, which wilt be found to give, at least, as good a crop as double the quan- 
tity of dung atone, whilst it is much cheaper in the first cost, and saves much 
cartage, which is of the greatest moment to the farmer in spring. From its 
eflfects upon the oat crop of this season, where it was used as a manure for the 
turnip crop of 1842, at the rate of 3 cwt. per acre, it seems permanent — as the 
oats will bear a comparison with those which grew where the land was manured 
with 40 cubic yards of farm-yard dung, and the hay ci'op, at this time, looks 
as strong and forward as any in the same field. Potatoes manured with guano, 
or dressed with sulphate and nitrate of soda, appear also to be improved in health, 
and the tubers so grown are less apt to fail when cut and planted the following 
season. 

Experanent II. — On Hay. 

Effect of top-dressings of various substances upon three years old Grass, 
mostly Timothy, cut for hay in 1843 ; top-dressed on the 3d of June ; cut on 
the 5th of August ; weighed when cut, and again weighed when stacked on the 
28th ot August. Quantity of ground under each dressing — One-eighth of an 
imperial acre. 



No. 



Dressings. 



Nothing 

Guano 

Compost of saw 
dust and coal tar 
Muriate of ammonia. 
Sulphate of urhie, 

Turnbull's 

Nitrate of soda 

Muriate of ammonia 

Common salt 

Nitrate of soda , 

Common salt 



ON ONE-EIGHTH OF AN IMPERIAL ACRE. PER. IMP. ACRE 



qrs. 



lbs. 



1 14 


3 10 


5 bush. 


2 6 


20 


3 


20 


3 


20 

1.5 

1 

15 

1 


9 
2 6 
4^ 
2 4 
4^ 



s. d. 



Oh bl 



Ib.s. 

1.344 

4660 

45C0 

3700 

3780 



lbs. 

3316 
3156 
2356 
2436 



2840 1496 
3760 2416 

3460 2116 



o S 






St. lbs. 
52 11 

7 



Soc 



c 
"'•5.= 



St. lbs. 

38 10 
43 9 



35 



v-S 



V 



ca 



"a S 



St. 

416 
752 

761 

560 

672 

424 

744 

696 



a a. 






£. s. d. 

6 18 8 

12 10 8 

12 13 8 

9 6 



11 12 



P*- 



2 CO 

Si v 



lbs. 
350 
275 

300 

265 

312 

265 

375 

350 



86 



EXPERIMENTS UPON HAY AND OATS. 



[Appendix, 



The part of the field where the above dressings were put is a stiff clay loam 
lying quite level upoa a sandstone rock, and has a south exposure. The 
dressings were late of being put on, and it was intended for green cutting for 
soiUng, but owing to the abundance of other feeding, the parts dressed were 
saved for hay. All the dressings except No. 3 had the effect of altering the 
colour to a dark green in the course of a week, and they all came away very 
strong and vigorous. No. 3 (the compost, see note 1°, p. 88,) had the effect of al- 
tering the colour in about three weeks after being applied, and came away so 
rapidly that it soon gained upon the others in point of strength and luxuriance 
of stems and leaves. It will be seen from the tables that Nos. 4 and 6 gave 
less hay from 1000 lbs. green cut, when used alone, than any of the others ; but 
with the addition of common salt 1000 lbs. gave more than any of the other 
dressed portions. Sulphated urine may be considered a salt of ammonia, all 
of which salts have been found to give greater bulk than almost any other ap- 
plication of salts applied to green produce, but they have invariably been found 
here to give less dry hay when used by themselves. The extra produce from 
the sulphated urine is probably owing to its compound nature. It appears from 
the above, therefore, that the most profitable way of using these salts is by 
viixing them loith others, and that the more compound the mixture is the better will 
be t/ie crop* 

Experiment III. — On Oats. 

Effects of guano upon Oats (potato), sown on the l7th of April ; cut and 
weighed on the 15th of September. Thrashed, cleaned, and weighed on the 
24th of October. 



1 


•6 


c 


S G 

b 


■is« 


is . 

2? 


s 
2 


o 


a 
2 






a. 




M ?<^ 




Jj .c 


to 


a> 


60 


No. 


Dressing. 


a) 




OS? 


- Si; 


O 1; 


■ol 


is 


o 

9) 






ts 




-G sVv_ 


S O CO 


x: *- 


■a = 




s 






a 
aJ 

D 

a? 


O 

O 


^ .S 
> C 3 


U C C 


^1 


5 CI. 


o aj 


u 
o 

a 






qrs. 


s. d. 


lbs. 


lbs. 


lbs. 


lbs. 


bush. lbs. 


bush. lbs. 


1 
2 


Guano 


3 


7 6 


3300 
2120 


653 
539 


1045 
749 


40 
42 


16 13 
12 35 


3 20 


Nothing 



Note. — The above quantities were applied to and reaped from one-fourth of 
an imperial acre. 

The portion of the field upon which the above oats were grown is a deep 
stiff yellow clay, super-incumbent upon sandstone rock. It has been thoroughly 
drained for a number of years. It had been sown Avith wheat on the 20th of 
January, 1843, top dressed with guano at the same time, which was harrowed 
in, but owing to the dampness and constant change from frost and thaw, the 
greatest part of the wheat failed, and was ploughed up on the 15th of April, and 
potato oats sown upon it on the 17th of that month. The oats brairded all 
alike, showing no difference in point of earliness ; but by the 9th of June a 
most remarkable alteration had taken place, the portion which had been dressed 
with guano for the wheat taking the lead of the undressed portion, and being 
of a dark green colour with broad leaves, and covering the ground well ; whilst 
that which had no dressing was brown and stinted in comparison, and the 
ground not half covered. The two portions continued throughout the season to 
present the same difference in their appearance, and at the time of cutting tliere 
was more than a foot in length of straw in favour of the dressed portion. It 
will be seen from the table, however, that although the guano had the effect of 
giving more bushels per acre, the bushels were lighter in weight by 2 lbs. than 
the grain from the undressed. It may be remarked, however, that had common 

* See on this subject of mixtures the Author's Elements of Agricultural Chemittry and 
Geology^ p. 149. 



No. X.] 



EXPERIMENTS UPON OATS AND TURNIPS. 



87 



salt been mixed with the g:uano, there is reason to believe, from other trials, 
that the grain would not have been deficient in weight per bushel. Ammonia- 
cal salts should at no time be dressed upon grain crops, without, at the same 
time, adding, according lo the composition of the soil upon which such crops 
are grown, such other inoi'ganic ingredients as may be required. Few soils, at 
least in this part of tlie countiy, appear able to supply these in sufficiency to the 
plants — particularly the phosphates, which seem always deficient. At least the 
addition of bone-dust or animal charcoal seems always to improve the crops to 
which they are applied. 

Experiment IV. — 0?i Turnips. 
Comparative effects of guano, farm-yard manure, bone-dust, and animal char- 
coal, by themselves and in mixtures,' on Turnips of different varieties ; lifted, 
topped, tailed, and weighed, in Nov., 1843. 



ON AN EIGHTH OP AN IMPERIAL ACRE. 



lON AN IMP. A ORE, 



p^Q 'Variety of turnips and.'pjjj^^ q, 



kind oi luaimies. 



ISiOWing. 



SWEDISH. 

C Farm-yard manure.... 

1 < jfciuano 

C Animal cliarcoal' 

UFarm-yard manure... 

2 < Giiduo 

C lllalf-incli bones 

3 Farm-yard manure . . . . 

4 iGuano 

5 llall'-inch bones 



PURPLE-TOP VELLOW. 

Guano 

i>iing 

Bones 

Farm-yard manure... 

Guano ... 

Farm-yard manure... 

Bone-dust .. . 

Farm yard manure... 

Guano 

Animal charcoal 



JONES' YELLOW TOP 

Farm-yard manure... 

Animal cliarcoal 

Farm-yard manure... 

Bone-dust 

Farm-yard manure.... 
tiul(.)tiale of Soda, as a 

top dressing 

Farm-yard manure... 

Guano 

Farm-yard manure.... 

Guanot 

Animal charcoal 

Compost of coal tar 

and saw-dust 



June 
5 to 7 



13 



17 



I Cost of 
Quantity of m.anures, 
manure exclusive of 
applied. cartage. 



21 



29 



2^ cub. yds. 

42 lbs. 

70 lbs. 

2.^ rub. yds. 

42 lbs. 

2^ bushels. 

5' cub. yds. 

70 lbs. 

5 bushels. 



.56 lbs. 

4§ cub. yds. 

ih bushels. 

2i cub. yds. 

2S lbs. 

2^ cub. yds. 

li bushels. 

'4 yds. 

28 lbs. 
42 lbs. 



3f yds. 
70 lbs. 
3| yds. 
1^ bushels. 

3f vds. 
20 ibs. 

3i yds. 
70 lbs. 
2k vds. 
42 ibs. 
li cwt. 

8 bushels. 



Produce. 



Pro- 
duce. 




10 




18 8;» 

2 6< 

18 9> 

3 0^ 

19 9/ 

1 OC 



6 3 

12 6: 

3 9 

5 



3 10 



ts. cts. qrs 
5 6 Oi 

4 19 




10 



4 18 3 

4 

3 1 1 

3 10 



3 5 
5 

2 

2 13 

3 12 3i 



ts. cte 
42 9 



33 17 
32 



25 14 



28 

26 16 

24 

36 



Value of 

produce 

at 15s. 

per ton. 



£. s. d. 
31 7 



39 1229 19 3 



•25 7 11 
6 



824 



14 2 6 

13 8 

12 

18 



25 10 12 15 
3J 1019 15 



32 
24 9 

28 



16 

12 4 6 

14 

13 
9 

17 1 
10 13 6 

14 11 






The field upon which the above turnips were grown is a light gravelly loam, 
super-incumbent upon a deep gravelly till. The greater part of the field was 
trenched with the spade, and all drained with tiles and soles 30 inches deep and 
20 feet apart, in the winter of 1841 and 1842, and in the preparation for the tur- 

• The animal charcoal here used is the refuse of the sugar refiners, and contains about 
fib. of its weight of bone-earth. 
t This part of the field was trenched. 



88 EXPERIMENTS UPON TURNIPS. [Appendix^ 

nip crop in 1842 and 1843, what had not been trenched was subsoiled. The 
turnip crop was sown at different times, as noticed in the tables. All the parts 
brairded well and healthy, and continued to grow without intermission througli 
the season. The field contains about 11 acres imperial, and the crop was most 
luxuriant, so much so, that the lightest turnips in any part of the field would 
have been reckoned good. The field was drilled for the crop with the double 
mould plough at 30 inches apart, for swedes and purple top-yelbw, and 26 and 28 
inches for Jones^ yellmv, which variety is remarkable for very small tops, and, in 
consequence, may be drilled nearer. The difference in the appearance of the 
turnips, where the various manures and mixtures had been applied, was very 
mai-ked. Wherever guano had been applied, the tops were larger than any of 
the others, except No. 3 of the table {Jones^ ijellou^), upon which sulphate of soda 
was top-dressed, after the plants were thinned. The crop upon this portion was 
remarkable for luxuriance of tops and large bulbs, and gave a very good crop.* 
No. 6 of the table (Jones' yellow), was upon spade-trenched land, and 
is the only lot where a comparison can be made between trenching and subsoil- 
ing. Where bone dust was used the tops were not so large, and where the ani- 
mal charcoal had been added the lops were least of all and the bulbs largest. Upon . 
all the varieties of soils in this farm, the application of animal charcoal or bone I 
dust has been of great benefit to all crops — to wheat, barley, oats, hay, and grass ** 
— the crops being bulkier and of superior quality, especially upon soils superin- 
cumbent on trap rock, giving an evidence that all such soils upon this estate are 
in want of phosphates. This has also been proved by the analysis of several — 
none of them giving more than a trace of phosphates, and some of them none at 
all. Upon all these soils animal charcoal or bones seem to be indispensable, 
because the gi'ain crops cannot be matured without phosphates of lime and 
magnesia. It appears from the many experiments that have been made here, 
that guano does not contain a sufficiency of the phosphates to supply the crops 
to which it is usually applied, and which, from the greater luxuriance of growth 
its application at all times induces, would be required in greater quantity accord- 
ing to the bulk of crop. A portion of the animal charcoal of tlie sugar refiners 
bemg mixed with it at the time of sowing, will supply the deficiency, and at all 
places inland from the sea, common salt will be found a valuable addition. The 
cultivator who is obliged from deficiency of farm-yard manure to use guano will 
find that by taking one-half of his usual quantity of farm-yard manure per acre, 
and making up for the other half by the addition of 2 to 4 cwts. of guano, his 
crops will be, at least, as bulky, and his after-crops as good, as if he had used 
40 cubic yards of good dung. Guano, however, should not be used by itself 
upon soils that do not contain a certain amount of vegetable matter (i. e. on poor 
sharp soils), but it will in all cases be found an invaluable manure for thorough- 
drained moss soils. 

Notes. — 1^. The compost of coal-tar and saw-dust used in the preceding experiments is 
composed of saw-dust or moss 40 bushels, coal-tar 20 gallons, bone-dust 7 bushels, sulphate 
of soda 1 cwt., sulphate of magnesia 1^ cwt., and common salt 1^ cwt., put togetlier in a 
heap, with 20 busliels of quicklime, and allowed to ferment and heat for three weeks, when 
it is turned, and again allowed to ferment, and is then fit for use. 

2^. In using the nitrate of soda for the last four years in the garden, it has been found 
that top dressing the leeks- in* the month of August or September enabled them to resist the 
effects of winter, whilst those that were not so dressed have invariably failed, and gone to 
decay early in the season ; at the same time, it increases their bulk in a remarkable man- 
ner. Knowing this effect upon leeks, — a crop that if grown to a large size has a great 
tendency to rot and fail in winter, — might it not have the same effect upon autumn sown 
wheats if dressed with it after they are brairded 7 This hint is merely thrown out as worthy 
of trial, as the salt appears to have the power of toughening the fibre or otherwise enabling 
the plants to withstand the rigours of winter, and in this way might, perhaps, prevent the 
wheat crop from failing in winter, which is often the case, to the great loss and disappoint- 
ment of the farmer 

Wm. Fleming. 

Barochan, Feb., 1844. 

* Sulphuric acid and the sulphates appear to exercise a marked action oa the turnip crop. — J. 



No. X] REMARKS UPON PRECEDING EXPERIMENTS. 89 

REMARKS. 

I submit these experiments to the reader without any lengthened comment. 
The experiments with guano are very seasonable, and will bo of much service 
to the thousands of practical men who are now likely to try this valuable 
manure. 

There are three interesting general observations of Mr, Fleming, to which 
alone I would direct especial attention — 

1°. That the potato sets did' not fail when powdered with gypsum, and that 
the more extensive trials of this substance which he recommends ought cer- 
tainly to be encouraged. 

2°. That potatoes dressed with guano, or with nitrate and sulphate of soda, 
appear to be improved in healtli, and are less apt to fail when cut and planted 
the following year. 

3'^. That his trap soils are supposed to be especially deficient in phosphates, 
and that the use of bones, in any form, always improved his crops upon these 
soils. 

These three observations are very interesting, and a careful study of the 
tables of results will lead the reader to make other interesting observations and 
deductions for himself. 

It is very satisfactory to me to have been able in this Appendix to incorporate 
the results of experiments performed on three successive years by one so skilful 
and zealous as Mr. Fleming, — conducted every year also with more care, and 
more likely, therefore, to lead to important conclusions. 

The subject of agricultural experiments has now been taken up so warmly 
and so successfully in almost every part of the country, that we may look for- 
ward with confidence to the gradual accumulation of a body of facts, out of 
which correct and practically useful principles may gradually be elicited. The 
large body of experimental results, which the prize offered last year by the 
Highland Society has brought before the public, shows how eagerly the en- 
lightened practical farmers of the present day will follow the guidance of such 
as are willing to show them how the art by which they live may be really and 
permanently improved. 



p I N I s. 



James P. Wright. Printer, 
122 Fulton street. 



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